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Haematological values during normal reproduction of the maternal and the fetal rabbit
Camp. Biochem. Phy.M. Vol. 87A, No. 2, pp. 479485, Printed
in Great
1987
0300-9629/87 $3.00 + 0.00 % 1987 Pergamon Journals Ltd
Britain
HAEMATOLOGICAL VALUES DURING NORMAL REPRODUCTION OF THE MATERNAL AND THE FETAL RABBIT K. KRIESTEN*, U. MURAWSKI* and W. SCHMIDTMANN? *Institute of Physiolo~cal Chemistry, University of Bonn, Nussallee 11,5300 Bonn, Federal Republic of Germany; t Medical University Clinic Bonn, Sigmund-Freud-StraDe 25, 5300 Bonn-Venusberg, Federal Republic of Germany
Abstract-l. Haematological values of non-pregnant/non-lactating, pregnant as well as lactating rabbits and 28-day-old fetuses were measured. 2. The haemoglobin content in does decreased during the observed periods from 122 + 8 g/l to 100 _+1I g/l. In 28-day-old fetuses it was 85 k 0 g/i. 3. The erythrocyte count in 28-day-old fetuses was 2.4 x 10’*/1.In the does, the erythrocyte count was 5.2 x lo’*/1 in week 4 of gestation. The erythrocyte volume in fetuses was about 45% higher than that of the doe. 4. In fetuses the leucocyte count was approximately one ninth that of the mother in week 4 of gestation (0.41 + 0.08 x 109/1vs 3.8 & 0.4 x 10’11).
INTRODUCX’ION
9204; 1424).Generally 100 cells were counted. Fetal blood was taken by opening the vena jugular& of six fetuses. The
There are limited numbers of studies of haematology of normal healthy female rabbits (Laird et al., 1970; Nomura et al., 1973; Srinivasan et al., 1979). Only a little data has been published on haematological parameters in pregnant and lactating rabbits. Normal gestation does mean a stress situation for maternal
differences between sampfe means were cabuiated by Student’s t-test (Sachs, 1984), for the significance of P < 0.05 the two side limit was chosen. RESULTS AND DISCUSSION
physiology. Thus, pregnancy elevates the plasma volume as well as the blood volume and red cell volume (Nuwayhid, 1979). The effects on other haematological parameters in this species are not well known. Because the embryo/fetus is a tissue allograft. pregnancy is an interesting object for an extensive study. Possibly the immunodeficiency in the mother reflects changes in the number of l~phocytes and other white blood cells as well as related factors. In this study we report on changes of red and white blood cell numbers, the mean erythrocyte volume and the platelet counts as well as the haemoglobin concentrations and the haematoc~t values. These parameters were also estimated in the blood of 28-day-old fetuses, except the white blood cell proportions. MATERIALS AND METHODS Studies were carried out on 10 healthy female rabbits (New Zealand White hybrids) between 7 and 9 months and an average weight of 3.9 + 0.4 kg. The animals were kept singly in iron cages and fed with dry fodder and tap water ad lib&m. Blood was taken from the central ear artery. The blood samples were collected in EDTA and analysed with the Coulter counter (S) and the Thrombo counter within 5 hr. Mean erythrocyte volume (MCV) and mean haemo~obin content of solitary erythrocytes (Hb,) as well as mean corpuscular haemoglobin content (MCHC) were calculated. Differential cell counts were made in blood smears which were stained with Giemsa and May-Griinwald (Merck:
The blood volume of non-pregnant/non-lactating rabbits with a mean body weight of 3.9 kg was nearly 0.22 1. Therefore the total haemoglobin (68,O~ dalton, Penzlin, 1980) content per animal from the mean Hb concentration of 122 g/1 (Table 1) was calculated at approximately 26.8 g. A similar Hb content of 122 g/I was also found in female rabbits of local strains (Srinivasan et al., 1979). Schmidtmann et al. (1973) found nearly the same Hb-concentration in male and female rabbits of different races with 124 g/l. Furthermore, the haematocrit of 0.35/l of our animals at stage 0 (Table I) was in the range 0.35-0.40/l from a New Zealand White outbreed line (Fischer, 1980), but differed slightly from the value of 0.42/l (Flindt, 1985). Other heamatological parameters of non-pregnant/ non-lactating animals can be taken from Tables I, 2 and 3. The mean percentage of lymphocytes in our animals was also higher than the neutrophil proportion. This is consistent with the observations of rabbits (local strains) by Srinivasan et al. (1979).
479
Gestation
Total haemoglobin concentration in the rabbits was decreased slightly, to about 26.2g in week 1 of pregnancy. This was connected with the diminished haemoglobin content at stage 1 (Table I), while the increase in the haematocrit value could result partly from a slight fluid-flux into the extra vasal room. Presumably, a higher release of erythrocytes (life-
K. KRIESTEN et al.
480 Table
stage
I
Haematological
values of rabbits
Heemiltocrit
Ileemoplohin
(l-1)
(R/l)
122 +
during
and lactation
(4 weeks) (N = IO)
MCHC
"he (Pa)
R.0
+
gestation
(R/l)
23.0
+ 2.7
351
329 + 32.1
1
0.36
+ 0.03
119
9.0
22.0
+
2
0.33
+ 0.03
125 +
17.0
26.0
+ 5.7
375 + 65.4
3
0.75
+ 0.04
119 +
11."
22.0
+ 2.2
337 + 26.1
4
0.74
2 0.04
110 +
12.0
21.2
+ 2.0
324 + 34.3
11.0
21.3
+ 2.R
348 + 17.9
l.A
non-pregnant non-lactating
+ 27.6
/
gestation
‘I6
+
100 +
4.”
21.7
+
1.3
rs4.5+ 31.1
103 +
x.0
21.9
+ 2.0
346 + 36.4
100 +
11.0
"1.3
+ 2.2
'114 + 32.4
1actotion
Table 2. Red and white blood cell and blood platelet counts in rabbits during gestation IPytt,rocytes
stwz
(x 10'2/1)
0
5.3
+
0.3
and lactation
WV
Lellcocytes
Platelets
(fl)
(x 109/l)
(//‘I blood)
64.6
+ 3.7
8.2
+ 1.0
243909
+ 70869
(N = 10)
non-pregnant non-lactating
5.4 + 0.B
67.5
+ 2.4
7.6 + 1.3
261363
+ 70176
4.8
+ 0.3
6R.4
+ 2.4
7.0 +
1.3
297666
+ 89923
5.4 + 0.5
66.5
+ 4."
5.9 +
1.6
356363
+ 5288fi
5.2 + O.6
64.5
+ 4.1
3.8 + 0.4
255111
+100030
4.5
6O.R
+
1.5
9.3
346250
+ 68923
4.6 + 0.3
62.R
+
1.4
4.7
fi3.R + 1.7
/
gestation
+ 0.4
+ 2.9
23X25
+ 78654
9.9 + 3.1
312375
+ 85765
10.7 + 2.8
256666
+ 93905
7.\3 +
1.2
lactation + 0.4
63.0
4.7 + 0.5
2
1.2
Table 3. White blood cell percentages
StaRe
Neutrophils
(%I 0
45.0
2
4.2
Lymphocytes (96) 50.5
+
11.8
in rabbits
Eosinophils (%) 2.0
+
1.4
during
gestation
and lactation
Basophila (%)
Yonocytes (%6)
2.0
1.5
+
1.4
+
0.6
64.0 +
2.0
2.5 + 0.7
1.5 + 0.7
1.0 + 0
58.0 +
2.1
2.0 + 1.4
1.0 + 0
1.5 + 0.7
5.0
59.0 +
17.0
1.5 + 0.7
0.5 + 0.4
3.0 + 0
27.0 +
1.5
70.5 +
1.5
1.0 +
0
1.5 + 0.5
5
26.0
+
3.5
67.0 +
1.l
1.5 + 0.5
3.0 2 2.0
0.5 + 0.5
5.4
2.0 + 0
1.6 + 0.4
1.0 + 0
1.0 + 0.5
1.0 + 0.5
0.5 + 0.5
2.5 +
1.0 + 0
2.5 + 1.5
1
29.5
2
2
26.0
+ 10.9
0.8
3
20.0 +
4
(N = IO)
non-pregnant non-lactating
gestation
6
28.5
+
3.6
65.5 +
7
17.5 +
3.5
66.1
8
36.5
4.5
52.0 + il.3
1.0
lactation
2
+ 11.9
1.5
/
Blood values in maternal and fetal rabbit span about 45-68days; Flindt, 1985) may in part account for this effect. A greater large-vessel haematocrit was observed in pregnant rabbits while no difference was seen in the whole body-haematocrit between pregnant and non-pregnant animals (Prince, 1982). Against this, the haematocrit significantly dropped to a minimum in week 2 of gestation in our rabbits (stages l-2, P < 0.05). This reflects a rise in the blood volume at the same time and is associated with a higher oxygen transport to the organs. An elevation of total blood volume in New Zealand White rabbits could be observed from day 10 to day 19 of gestation and should be about 45% higher near term (Nuwayhid, 1979). Mean corpuscular haemoglobin content (MCHC) and the mean haemoglobin concentration of solitary erythrocytes (Hb,) also showed similar trends (stages O-2, P < 0.02). The haematocrit of our animals decreased to a minimum of 0.36/l in week 2 of gestation, while the Hb content rose to a maximum at this stage. The Hb concentration in the sow comparatively decreased up to week 9 of gestation (Hoffmann et al., 1980). In the same way, the erythrocyte volume of this species dropped, up to week 8 of pregnancy (Steinhardt et al., 1982). In weeks 3 and 4 of gestation, the haemoglobin content in our rabbits diminished (stages 2-4, P < 0.05) whilst the erythrocyte count increased in week 3 (stages 2-3, P < 0.01). The mean haemoglobin content of solitary erythrocytes (Hb,) also declined (stages 2-4, P < 0.02). For example, the lowest haemoglobin level of the sow was measured within week 14 of pregnancy too, in the same way the erythrocyte volume decreased about the time of gestation in this species (Steinhardt et al., 1982). Also, the erythrocyte count and the haemoglobin concentration in cows decreased from week 6 of pregnancy to parturition (Bostedt et al., 1974). The decrease of haemoglobin content in stage 4 of our rabbits was probably produced by a lower synthesis of these molecules as a result of a deficiency of iron, since the lowest content of this element was observed in week 4 of gestation (Kriesten et al., 1986). A decrease in the haematocrit value and haemoglobin concentration was also measured during human pregnancy (Hytten and Leitch, 1971; Peters, 1984). The decline of the erythrocyte number in our animals within week 4 of pregnancy (Table 2) could have resulted from a higher erythrocyte osmotic fragility (Magid et al., 1982) by virtue of the drop in albumin content (Morgan, 1964). On the other hand, it can be assumed that progesterone modifies the erythrocyte parameters by the regulation of erythropoesis during gestation (Gromadzka-Ostrowska et al., 1985). The platelet (life-span about 6 days ; Flindt, 1985) count rose in weeks 1 and 2 of gestation and reached the peak level in week 3 (stages O-3, P < 0.001; stages l-3, P < 0.01) (Table 2). Then the platelet number decreased to a minimum at stage 4 of gestation. The rise in platelet numbers in week 3 is not consistent with the gestational increase of the blood volume (Nuwayhid, 1979; Prince, 1982) in this period, but could be the result of a higher thrombopoesis. Our data show an average decline in platelet numbers of nearly 28.4% in week 4 of gestation. This could be in agreement with the increasing total blood volume at
481
that time of gestation and could be due to the changes of hormonal influence. A small decrease in the platelet count was also found throughout human pregnancy (Sejeny et af., 1975). A reduction of monoamineoxidase (EC 1.4.3.4) activity was reported in platelets during human pregnancy (Wahlund et al., 1986) which could also be affected in its velocity (I’,,,,,) in the platelets of pregnant rabbits. The leucocyte count was previously diminished in week 1 of gestation, in comparison to non-pregnant, non-lactating animals (Table 2). In contrast, an increase in total number of leucocytes occurred relatively early in human pregnancy (Pitkin and Witte, 1979). The fall of leucocytes in pregnant rabbits is probably produced by a decrease in the neutrophil proportion (stages O-l, P < 0.0001) and the basophils as well as the monocytes. Whereas the lymphocytes and eosinophil cell numbers became elevated at the same time (Table 3). In the following week the leucocyte count showed a further decline (stages O-2, P < 0.002). This decrease is mainly produced by a drop in numbers of neutrophils (stages l-3, P -c0.02) eosinophil cells (stages l-3, P < 0.01) and basophil cells (stages l-3, P < 0.0001; stages O-3, P < O.OOOl),whilst the monocyte numbers were significantly elevated in week 3 of gestation (stages 2-3, P < 0.0001; stages O-3, P < 0.0001). An elevation of the monocyte number was also observed in human pregnancy in the second trimester (Pitkin and Witte, 1979). In the last week of pregnancy the leucocyte count of our animal collective showed a decrease (stages 1-4, P < 0.0001; stages 2-4, P c 0.0001; stages 3-4, P < O.OOl), whilst the lymphocyte numbers were significantly elevated at this stage (stages 3-4, P < 0.02). A marked decline in white blood cell numbers, to the lowest level in the pregnancy of chinchillas, was also observed before parturition (Gromadzka-Ostrowska et al., 1985). Generally, the lymphocytes in rabbit gestation were nearly in the same range as in human pregnancy (Pitkin and Witte, 1979). The decrease of leucocyte counts in our rabbits is probably the result of a reduction of the numbers of basophils and neutrophils. While the increase of neutrophils in human pregnancy probably resulted from the elevated levels of estrogen and corticosteroids (Pitkin and Witte, 1979) it is possible that these hormones do not have such marked effects on the stem cells of neutrophils in pregnant rabbits. The significant elevation of lymphocyte numbers in the last week of rabbit gestation (stages O-4, P -c0.0001; stages l-4, P < 0.0001; stages 2-4, P < 0.0001; stages 3-4, P < 0.05) would probablv be caused by an increase of the number of B 1ym;rhocytes. In contrast a slight decrease of total lymphocytes in primiparous cows was observed at parturition (Kashiwazaki et al., 1985). Whether there was also a change in the number of certain subpopulations of T lymphocytes in pregnant rabbits is still open to question. So, for example, the suppressor T lymphocytes (OKT 8 cells) (Hirahara et al., 1980; Cheney er al., 1984) as well as the percentage of OKT 4 cells (T helper cells) (Canepa et al., 1984), T lymphocytes which express for Fc-IgG (To cells) (Ong et al., 1983) and the number of T lymphocytes which carry trophoblastic glycoprotein-receptors (Sotnikova et al., 1985) were elevated during human pregnancy; but the total
482
K. KRIESTENet al.
number of T lymphocytes decreased in the course of human pregnancy (Knippel et al., 1984). The higher level of lymphocytes in our animal collective was presumably brought about by an increased number of B lymphocytes. The elevation of B lymphocytes in pregnant mice results mainly from the fetus itself (Newport and Carter 1983). On the other hand, T lymphocytes in rabbits could be important in the immune adaptation to pregnancy, they may play an essential role in embryo/fete-maternal immunological interaction. Because the embryo/fetus can be thought of as a tolerated semi-allograft, since one half of its MCH (major histocompatibility complex) antigens and/or other alloantigens are derived from the father and should be recognized by the mother as foreign (Beer and Billingham, 1974). It is possible that a depression of the cytolytic activity during gestation of rabbits may be due to the elevated level of progesterone (K. Kriesten et al., unpublished data) which presumably reduced the cell lysing capacity of T lymphocytes (effector cells) (Stites et al., 1983) and so is partially responsible for the tolerance of embryonal/fetal allografts in rabbits. In addition, alphafetoproteins, chorion gonadotrophin and placental lactogen in combination (Bischof et al., 1983) could also have inhibitory effects on lymphoblastogenesis of T cells in pregnant rabbits. Furthermore, uteroglobin in connection with transglutaminase (EC 2.3.2.13) should play a specific role in masking the antigenicity of the growing rabbit embryo during implantation (Murkherjee et al., 1982). The increase of monocytes in week 3 of gestation in our rabbits is comparable to the rise in that cell population within the second trimester in human pregnancy (Pitkin and Witte, 1979). It is not clear whether that cell population also has a reduced thromboblastin activity in pregnant rabbits (Oian et al., 1985). Monocytes of rabbits may also play a role in local activation of coagulation systems in pregnancy (especially in the utero-placental circulation). Monocytes could probably react with antibodies in the serum of pregnant rabbits, and this reaction could presumably provide a regulator signal for the suppression of T cell proliferation (Nieda et al., 1985). A marked increase of the monocyte/lymphocyte ratio was also observed in week 3 of gestation (Fig. I),
after this the ratio decreased. It is known that an excess of monocytes relative to the lymphocytes is even able to suppress some immune responses (Allison, 1978). Therefore, it can also be assumed, that a higher prostaglandin synthesis plays an essential role in these reactions (Kurland and Bockman, 1978). This probably represents a suppressive mechanism by which the allograft could be protected in rabbit gestation also. Whether the suppressor functions of monocytes and of some T cell subpopulations (mainly T helper cells) act in concert with other humoral factors (Stites et al., 1983) to protect the embryos/fetuses from rejection in rabbits, is still a field of speculation. In the blood of 28-day-old rabbit fetuses, the number of erythrocytes was about the half of that of the doe in week 4 of gestation (Table 4). The haemoglobin concentration was also relatively low compared to that of the mother at stage 4 of gestation. Whilst an increased mean erythrocyte volume (MCV) was noticed in 28-day-old fetuses, the Hb content of the solitary erthyrocytes (Hb,) was nearly the same as that of the doe. Similar values of mean corpuscular haemoglobin content (MCHC) were also found in rabbit fetuses and in the mothers. The haematocrit value was approximately one half of that of newborn rabbits (Harris et al., 1983) whilst the blood platelet count in the doe was nearly five times greater than that in the fetus. Whether at the same time, the width of platelets of the fetus was also changed, is still unsolved. A significantly lower leucocyte count was also found in the 28-day-old fetuses, compared with that of the mother at stage 4 (P < 0.0001). Lactation
The erythrocyte count showed a marked decrease in the 4 weeks of lactation which were monitored (stages 4-5, P <: 0.01; stages 4-6, P < 0.02; stages 4-7, P < 0.05) (Table 2). These findings could be connected with the loss of doe’s blood during and after parturition. Whilst a marked rise of erythrocyte number was observed in cows after parturition (Bostedt et al., 1974) the haematocrit values also diminished significantly after parturition in our rabbits (stages 45, P < 0.005; stages 4-6, P < 0.002; stages 4-7, P < 0.01; stages 4-8, P < 0.02) (Table 1). This is probably associated with a higher 0, release from haemoglobin to the tissue. At the same time the haematocrit values reached the nadir and were lower than those from pregnant as well as non-pregnant, Table 4. Haematological
gestation ’ lactation Fig. 1. Monocyte-lymphocyte ratios in gestation and lactation. The ratios were calculated as the mean of monocyte (%j over the mean of lvmohocvte Co?&)counts.
values of 28-day-old
fetuses
Blood values in maternal and fetal rabbit non-lactating animals. The haemoglobin concentration was also significantly lower in weeks 1 and 2 of lactation, in comparison with that during the gestation period (stages 4-5, P < 0.05; stages 4-6, P < 0.05). Against this, the haemoglobin content during human lactation rose steadily, apart from a slight decrease directly after parturition and was higher than in the course of pregnancy (Stirling et al., 1984). Also, the haemoglobin content in cows increased after parturition (Bostedt et al., 1974). In addition, the volume of erythrocytes in our rabbit collective further diminished in week 1 of this period (stages 4-5, P < 0.002) and showed an elevated level in the following weeks of lactation (stages 5-6, P ~0.01; stages 5-7, P < 0.001;stages 5-8, P < 0.002). Altogether the MCV was lower than the values of pregnant as well as non-pregnant, nonlactating animals. The decrease of the MCV in week 1 of lactation was in contrast with the results measured in mice (Miesel, 1978). The MCV of this species was immediately elevated after parturition. The MCV of sows was likewise markedly higher on day 10 of lactation and rose further from day 28 to day 35 during the course of lactation (Steinhardt et al., 1982). The values of mean corpuscular haemoglobin concentration (MCHC) was slightly higher during the early lactation period compared with that in the second half of gestation (Table l), whereas the haemoglobin content of solitary erythrocytes (Hb,) showed an unimportant decrease in comparison with the mean value of rabbits in week 4 of gestation. Moreover, the Hb, was lower than the values found in rabbits in the first half of gestation and also lower than those in non-pregnant, non-lactating animals (Table 1). The number of platelets in our animal collective reached a minimum in week 2 of lactation (stages 5-6, P < O.Ol), rose again in week 3 and dropped once more in week 4 (stages 5-8, P < 0.002) (Table 2). The number of these cells showed a higher trend during lactation compared to the last week of gestation. A rise in platelet counts was also measured in humans after delivery (Stirling et al., 1984). The number of leucocytes was significantly higher during lactation than during the course of gestatron (stages 4-5, P < 0.001; stages 4-6, P < 0.01; stages 4-7, P < 0.0001; stages 4-8, P < 0.001). Thereby, the leucocyte count showed a trough in week 2 of the lactation period (Table 2). The decrease of leucocytes was probably provoked by the diminished monocyte and eosinophil numbers at the time of lactation (stage 5-6, P < 0.001 resp. stages 5-6, P < 0.01) (Tables 2 and 3). The eosinophils showed a higher tendency during lactation compared with week 4 of gestation (Table 3). The peak level of this cell population could result from an allergic response to milk as conjectured for the cow (Brewer, 1957). However, the neutrophil cells of our rabbits showed similar values in the second week of lactation as during the gestation period and reached a maximum in week 4 of this period (stages 5-8, P < 0.001; stages 7-8, P < 0.0001) (Table 3). Whilst the basophil cell proportion was markedly elevated in week 1 of lactation, this cell population dropped in the following weeks of observation (stages 556, P < 0.05; stages 5-8, P < 0.01; stages 67 P < 0.01; stages 68, P < 0.001
483
stages 7-8, P < 0.01). The percentage of monocytes decreased significantly in week 1 of lactation (stages 4-5, P < 0.001) and was twice that of stage 5 in week 2 (Table 3) then increased to a maximum level in week 4 (stages 5-6, P < 0.01; stages 5-8, P < 0.01; stages 6-7, P < 0.01; stages 6-8, P < 0.01; stages 7-8, P < 0.001) whereas the lymphocytes were significantly lower during the lactation period compared with week 4 of gestation (stages 4-5, P < 0.0001; stages 4-6, P < 0.02; stages 4-8, P < 0.0001). This cell population reached a trough in week 4 of lactation (stages 5-8; P < 0.001; stages 68, P < 0.01; stages 7-8, P < 0.02). This suggests the possibility of a decreased maternal immune response in lactating rabbits as observed during the lactation of mice (Gamble and Ferguson, 1982) whilst a marked increase in the lymphocyte count in primiparous cows was noticed after parturition (Kashiwazaki et al., 1985). The monocyte-lymphocyte ratio reached a minimum in week 1 of lactation and rose slightly in week 2 (Fig. 1). Then the ratio decreased once more in the following week and showed a peak in week 4 of this period. This maximum appears to be related to an immunosuppresive mechanism. Whether the changes of neutrophils and lymphocytes in pregnant and lactating rabbits alone may be indicative of health or illness, must be examined by further investigations. However, heterophil cells and lymphocytes alone should show whether a rabbit is normal or ill (Hinton et al., 1982) as when all the blood cells were taken into account. SUMMARY
Haematological values of non-pregnant/nonlactating, pregnant as well as lactating rabbits (New Zealand White hybrid, N = IO) and of 28-day-old fetuses (N = 6) were measured. The erythrocyte count decreased in week 2 of pregnancy and was slightly elevated in the second half of this period. A marked decrease occurred in week 1 of lactation. The haemoglobin content dropped slightly in the second half of gestation and further decreased in week 1 of lactation. The haematocrit value showed only a slight decline during the gestation period, compared with the values of nonpregnant/non-lactating animals and was not significantly diminished in the lactation phase. The leucocyte count was lower during gestation compared to the values of non-pregnant/nonlactating animals. This cell population was slightly higher during the lactation period in comparison with that of the animals in week 4 of pregnancy. The platelet count showed a marked decrease in week 4 of gestation and reached a peak level in week 1 of the lactation phase. In 28-day-old fetuses, the erythrocyte count was very low, at 2.3 x lO”/l. The mean erythrocyte volume of the fetus was about 45% higher than that of the doe in week 4 of gestation. The haematocrit was nearly 21% lower than that of the mother animal at the end of pregnancy. The haemoglobin content was also relatively low in comparison to that of the doe. The leucocyte count was approximately one ninth that of the mother in week 4 of gestation. The platelet
K. KRIESTEN et al.
484 number mother
of the fetus
was
about
one fifth
that
of the
in week 4 of pregnancy.
Acknowledgements-The Renate Langer (MTLA) techniques.
authors wish to thank Miss for her help with haematological
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I
Kriesten K., Schmidtmann W. and Murawski U. (1986) Iron and copper concentrations in the maternal and fetal serum, in the placenta and amniotic fluid during the reproductive stadium as well as in the milk of rabbits, Camp. Biochem. Physiol. 83A, 291-296. Kurland J. and Bockman R. (1978) Prostaglandin E production by human monocytes and mouse peritoneal macrophages. J. exp. Med. 147, 952-957. Laird W. C.: Fox R. R., Mitchell P. B., Blau M. E. and Schultz S. H. (1970) Effect of strain and aae on some hematological parameters in the rabbit. AmyJ. Physiol. 218, 1613-1617. Magid S. M., Perlin M. and Gottfried L. E. (1982) Increased erythrocyte osmotic fragility in pregnancy. Am. J. Gbsref. Gynecol. 144, 91O-914. Miesel G. (1978) Normalwerte bei wachsenden und laktierenden Mlusen. Thesis: Tiermed., University of Munich. Morgan H. E. (1964) Passage of transferrin, albumin and gamma globulin from maternal plasma to foetus in the rat and rabbit. J. Physiol. 171, 26-41. Mukherjee B. A., Ulane E. R. and Agrawal K. A. (1982) Role of uteroglobin and transglutaminase in masking the antigenicity of implanting rabbit embryos. Am. J. Reprod. Immun. 2, 1355141. Newport A. and Carter J. (1983) Changes in T and B lymphocyte subpopulations in the lymph nodes draining the uterus in pregnant mice. J. Reprod. Fertil. 67, 433440. Nieda M., Juji T. and Imao S. (1985) Allogeneic suppressive effects of pregnancy sera on monocytes of responding cells in mixed lymphocyte reactions. J. clin. Invest. 76, 147771484. Nomura G., Tamura M., Hirohashi K. and Nagase S. (1973) Comparison of constitution of blood of several experimental animals with human blood. Exper. Anim. 22, 308-321. Nuwayhid S. (1979) Hemodynamic changes during pregnancy in the rabbit. Am. J. bbslet. Gynecol. 135,59&596. 0ian P.. Omsie I.. Maltau M. J. and 0sterud B. (1985) Reduced thiomboplastin activity in blood monocytes and reduced sensitivity to stimuli in vitro of blood monocytes from pregnant women. Br. J. Haemal. 59, 1333137. Ong S. K., Grieco H. M. and Goel 2. (1983) Increased ‘T lymphocyte’ bearing Fc receptors for IgG in pregnancy. Int. Archs Allergy appl. Immun. 70, 220-224. Penzlin H. (1980) Lehrbuch der Tierphysiologie, 3rd edn. Gustav Fischer, Stuttgart. Peters H.-W. (1984) Haematocrit and haemoglobin levels in adult males and in pregnant and non-pregnant females in northern Ethiopia. Ethiop. Med. J. 22, 17-27. Pitkin M. and Witte L. D. (1979) Platelet and leucocyte counts in pregnancy. J. Am. Med. Assoc. 242,26962698. Prince H. (1982) Blood volume in pregnant rabbits. Q. J. exp. Physiol. 67, 87-95. Sachs L. (1984) Angewand/e Statistik, 6th edn. Springer, Berlin. Schmidtmann W., Loeven B., Koch M. and Oest S. (1973) Normalwerte von Versuchskaninchen. Arztl. Lab. 19, 351-360. Sejeny S. A., Eastham R. D. and Baker S. R. (1975) Platelet counts during normal pregnancy. J. clin. Pathol. 28, 812-813. Sotnikova N. Yu., Babakova L. A. and Petrov R. V. (1985) Lymphocyte receptors for trophoblastic /J-glycoprotein. -_ _ B&i. eksp. Biol.-Med. 99, 326327. Srinivasan R.. Nataraian N. and Shinmuaam M. A. (1979) A study on the no-&al haematology of rabbits. Indian Vet. J. 56, 55&553. Steinhardt M., Furcht G., Fiissel A. -E., Grumbach R. and Hiiriigel K. (1982) Beziehungen zwischen einigen MengenmaDen des Blutes von Sauen in der Trachtigkeit und Laktation. Archs exp. Vet Med. 36, 203-209.
Blood values in maternal and fetal rabbit Stirling Y., Woolf L., North S. R. W., Seghatchian J. M. and Meade W. T. (1984) Haemostasis in normal _ preg_ _ nancy. Thromb. Ha&os; 52, 176-l 82. Stites D. P., Bugbee S. and Siiteri P. K. (1983) Differential actions of progesterone and cortisol on lymphocyte and monocyte interaction during lymphocyte activation-
485
relevance to immunosuppression in pregnancy. J. Reprod. Immun. 5. 215-228. Wahlund L.-O., SIHf J., Eneroth-Grimfors E., Nilsson B. A. and Bevegard S. (1986) Reduced platelet MAO activity during pregnancy. Acra Physiol. &and. 126, 135-139.
in Great
1987
0300-9629/87 $3.00 + 0.00 % 1987 Pergamon Journals Ltd
Britain
HAEMATOLOGICAL VALUES DURING NORMAL REPRODUCTION OF THE MATERNAL AND THE FETAL RABBIT K. KRIESTEN*, U. MURAWSKI* and W. SCHMIDTMANN? *Institute of Physiolo~cal Chemistry, University of Bonn, Nussallee 11,5300 Bonn, Federal Republic of Germany; t Medical University Clinic Bonn, Sigmund-Freud-StraDe 25, 5300 Bonn-Venusberg, Federal Republic of Germany
Abstract-l. Haematological values of non-pregnant/non-lactating, pregnant as well as lactating rabbits and 28-day-old fetuses were measured. 2. The haemoglobin content in does decreased during the observed periods from 122 + 8 g/l to 100 _+1I g/l. In 28-day-old fetuses it was 85 k 0 g/i. 3. The erythrocyte count in 28-day-old fetuses was 2.4 x 10’*/1.In the does, the erythrocyte count was 5.2 x lo’*/1 in week 4 of gestation. The erythrocyte volume in fetuses was about 45% higher than that of the doe. 4. In fetuses the leucocyte count was approximately one ninth that of the mother in week 4 of gestation (0.41 + 0.08 x 109/1vs 3.8 & 0.4 x 10’11).
INTRODUCX’ION
9204; 1424).Generally 100 cells were counted. Fetal blood was taken by opening the vena jugular& of six fetuses. The
There are limited numbers of studies of haematology of normal healthy female rabbits (Laird et al., 1970; Nomura et al., 1973; Srinivasan et al., 1979). Only a little data has been published on haematological parameters in pregnant and lactating rabbits. Normal gestation does mean a stress situation for maternal
differences between sampfe means were cabuiated by Student’s t-test (Sachs, 1984), for the significance of P < 0.05 the two side limit was chosen. RESULTS AND DISCUSSION
physiology. Thus, pregnancy elevates the plasma volume as well as the blood volume and red cell volume (Nuwayhid, 1979). The effects on other haematological parameters in this species are not well known. Because the embryo/fetus is a tissue allograft. pregnancy is an interesting object for an extensive study. Possibly the immunodeficiency in the mother reflects changes in the number of l~phocytes and other white blood cells as well as related factors. In this study we report on changes of red and white blood cell numbers, the mean erythrocyte volume and the platelet counts as well as the haemoglobin concentrations and the haematoc~t values. These parameters were also estimated in the blood of 28-day-old fetuses, except the white blood cell proportions. MATERIALS AND METHODS Studies were carried out on 10 healthy female rabbits (New Zealand White hybrids) between 7 and 9 months and an average weight of 3.9 + 0.4 kg. The animals were kept singly in iron cages and fed with dry fodder and tap water ad lib&m. Blood was taken from the central ear artery. The blood samples were collected in EDTA and analysed with the Coulter counter (S) and the Thrombo counter within 5 hr. Mean erythrocyte volume (MCV) and mean haemo~obin content of solitary erythrocytes (Hb,) as well as mean corpuscular haemoglobin content (MCHC) were calculated. Differential cell counts were made in blood smears which were stained with Giemsa and May-Griinwald (Merck:
The blood volume of non-pregnant/non-lactating rabbits with a mean body weight of 3.9 kg was nearly 0.22 1. Therefore the total haemoglobin (68,O~ dalton, Penzlin, 1980) content per animal from the mean Hb concentration of 122 g/1 (Table 1) was calculated at approximately 26.8 g. A similar Hb content of 122 g/I was also found in female rabbits of local strains (Srinivasan et al., 1979). Schmidtmann et al. (1973) found nearly the same Hb-concentration in male and female rabbits of different races with 124 g/l. Furthermore, the haematocrit of 0.35/l of our animals at stage 0 (Table I) was in the range 0.35-0.40/l from a New Zealand White outbreed line (Fischer, 1980), but differed slightly from the value of 0.42/l (Flindt, 1985). Other heamatological parameters of non-pregnant/ non-lactating animals can be taken from Tables I, 2 and 3. The mean percentage of lymphocytes in our animals was also higher than the neutrophil proportion. This is consistent with the observations of rabbits (local strains) by Srinivasan et al. (1979).
479
Gestation
Total haemoglobin concentration in the rabbits was decreased slightly, to about 26.2g in week 1 of pregnancy. This was connected with the diminished haemoglobin content at stage 1 (Table I), while the increase in the haematocrit value could result partly from a slight fluid-flux into the extra vasal room. Presumably, a higher release of erythrocytes (life-
K. KRIESTEN et al.
480 Table
stage
I
Haematological
values of rabbits
Heemiltocrit
Ileemoplohin
(l-1)
(R/l)
122 +
during
and lactation
(4 weeks) (N = IO)
MCHC
"he (Pa)
R.0
+
gestation
(R/l)
23.0
+ 2.7
351
329 + 32.1
1
0.36
+ 0.03
119
9.0
22.0
+
2
0.33
+ 0.03
125 +
17.0
26.0
+ 5.7
375 + 65.4
3
0.75
+ 0.04
119 +
11."
22.0
+ 2.2
337 + 26.1
4
0.74
2 0.04
110 +
12.0
21.2
+ 2.0
324 + 34.3
11.0
21.3
+ 2.R
348 + 17.9
l.A
non-pregnant non-lactating
+ 27.6
/
gestation
‘I6
+
100 +
4.”
21.7
+
1.3
rs4.5+ 31.1
103 +
x.0
21.9
+ 2.0
346 + 36.4
100 +
11.0
"1.3
+ 2.2
'114 + 32.4
1actotion
Table 2. Red and white blood cell and blood platelet counts in rabbits during gestation IPytt,rocytes
stwz
(x 10'2/1)
0
5.3
+
0.3
and lactation
WV
Lellcocytes
Platelets
(fl)
(x 109/l)
(//‘I blood)
64.6
+ 3.7
8.2
+ 1.0
243909
+ 70869
(N = 10)
non-pregnant non-lactating
5.4 + 0.B
67.5
+ 2.4
7.6 + 1.3
261363
+ 70176
4.8
+ 0.3
6R.4
+ 2.4
7.0 +
1.3
297666
+ 89923
5.4 + 0.5
66.5
+ 4."
5.9 +
1.6
356363
+ 5288fi
5.2 + O.6
64.5
+ 4.1
3.8 + 0.4
255111
+100030
4.5
6O.R
+
1.5
9.3
346250
+ 68923
4.6 + 0.3
62.R
+
1.4
4.7
fi3.R + 1.7
/
gestation
+ 0.4
+ 2.9
23X25
+ 78654
9.9 + 3.1
312375
+ 85765
10.7 + 2.8
256666
+ 93905
7.\3 +
1.2
lactation + 0.4
63.0
4.7 + 0.5
2
1.2
Table 3. White blood cell percentages
StaRe
Neutrophils
(%I 0
45.0
2
4.2
Lymphocytes (96) 50.5
+
11.8
in rabbits
Eosinophils (%) 2.0
+
1.4
during
gestation
and lactation
Basophila (%)
Yonocytes (%6)
2.0
1.5
+
1.4
+
0.6
64.0 +
2.0
2.5 + 0.7
1.5 + 0.7
1.0 + 0
58.0 +
2.1
2.0 + 1.4
1.0 + 0
1.5 + 0.7
5.0
59.0 +
17.0
1.5 + 0.7
0.5 + 0.4
3.0 + 0
27.0 +
1.5
70.5 +
1.5
1.0 +
0
1.5 + 0.5
5
26.0
+
3.5
67.0 +
1.l
1.5 + 0.5
3.0 2 2.0
0.5 + 0.5
5.4
2.0 + 0
1.6 + 0.4
1.0 + 0
1.0 + 0.5
1.0 + 0.5
0.5 + 0.5
2.5 +
1.0 + 0
2.5 + 1.5
1
29.5
2
2
26.0
+ 10.9
0.8
3
20.0 +
4
(N = IO)
non-pregnant non-lactating
gestation
6
28.5
+
3.6
65.5 +
7
17.5 +
3.5
66.1
8
36.5
4.5
52.0 + il.3
1.0
lactation
2
+ 11.9
1.5
/
Blood values in maternal and fetal rabbit span about 45-68days; Flindt, 1985) may in part account for this effect. A greater large-vessel haematocrit was observed in pregnant rabbits while no difference was seen in the whole body-haematocrit between pregnant and non-pregnant animals (Prince, 1982). Against this, the haematocrit significantly dropped to a minimum in week 2 of gestation in our rabbits (stages l-2, P < 0.05). This reflects a rise in the blood volume at the same time and is associated with a higher oxygen transport to the organs. An elevation of total blood volume in New Zealand White rabbits could be observed from day 10 to day 19 of gestation and should be about 45% higher near term (Nuwayhid, 1979). Mean corpuscular haemoglobin content (MCHC) and the mean haemoglobin concentration of solitary erythrocytes (Hb,) also showed similar trends (stages O-2, P < 0.02). The haematocrit of our animals decreased to a minimum of 0.36/l in week 2 of gestation, while the Hb content rose to a maximum at this stage. The Hb concentration in the sow comparatively decreased up to week 9 of gestation (Hoffmann et al., 1980). In the same way, the erythrocyte volume of this species dropped, up to week 8 of pregnancy (Steinhardt et al., 1982). In weeks 3 and 4 of gestation, the haemoglobin content in our rabbits diminished (stages 2-4, P < 0.05) whilst the erythrocyte count increased in week 3 (stages 2-3, P < 0.01). The mean haemoglobin content of solitary erythrocytes (Hb,) also declined (stages 2-4, P < 0.02). For example, the lowest haemoglobin level of the sow was measured within week 14 of pregnancy too, in the same way the erythrocyte volume decreased about the time of gestation in this species (Steinhardt et al., 1982). Also, the erythrocyte count and the haemoglobin concentration in cows decreased from week 6 of pregnancy to parturition (Bostedt et al., 1974). The decrease of haemoglobin content in stage 4 of our rabbits was probably produced by a lower synthesis of these molecules as a result of a deficiency of iron, since the lowest content of this element was observed in week 4 of gestation (Kriesten et al., 1986). A decrease in the haematocrit value and haemoglobin concentration was also measured during human pregnancy (Hytten and Leitch, 1971; Peters, 1984). The decline of the erythrocyte number in our animals within week 4 of pregnancy (Table 2) could have resulted from a higher erythrocyte osmotic fragility (Magid et al., 1982) by virtue of the drop in albumin content (Morgan, 1964). On the other hand, it can be assumed that progesterone modifies the erythrocyte parameters by the regulation of erythropoesis during gestation (Gromadzka-Ostrowska et al., 1985). The platelet (life-span about 6 days ; Flindt, 1985) count rose in weeks 1 and 2 of gestation and reached the peak level in week 3 (stages O-3, P < 0.001; stages l-3, P < 0.01) (Table 2). Then the platelet number decreased to a minimum at stage 4 of gestation. The rise in platelet numbers in week 3 is not consistent with the gestational increase of the blood volume (Nuwayhid, 1979; Prince, 1982) in this period, but could be the result of a higher thrombopoesis. Our data show an average decline in platelet numbers of nearly 28.4% in week 4 of gestation. This could be in agreement with the increasing total blood volume at
481
that time of gestation and could be due to the changes of hormonal influence. A small decrease in the platelet count was also found throughout human pregnancy (Sejeny et af., 1975). A reduction of monoamineoxidase (EC 1.4.3.4) activity was reported in platelets during human pregnancy (Wahlund et al., 1986) which could also be affected in its velocity (I’,,,,,) in the platelets of pregnant rabbits. The leucocyte count was previously diminished in week 1 of gestation, in comparison to non-pregnant, non-lactating animals (Table 2). In contrast, an increase in total number of leucocytes occurred relatively early in human pregnancy (Pitkin and Witte, 1979). The fall of leucocytes in pregnant rabbits is probably produced by a decrease in the neutrophil proportion (stages O-l, P < 0.0001) and the basophils as well as the monocytes. Whereas the lymphocytes and eosinophil cell numbers became elevated at the same time (Table 3). In the following week the leucocyte count showed a further decline (stages O-2, P < 0.002). This decrease is mainly produced by a drop in numbers of neutrophils (stages l-3, P -c0.02) eosinophil cells (stages l-3, P < 0.01) and basophil cells (stages l-3, P < 0.0001; stages O-3, P < O.OOOl),whilst the monocyte numbers were significantly elevated in week 3 of gestation (stages 2-3, P < 0.0001; stages O-3, P < 0.0001). An elevation of the monocyte number was also observed in human pregnancy in the second trimester (Pitkin and Witte, 1979). In the last week of pregnancy the leucocyte count of our animal collective showed a decrease (stages 1-4, P < 0.0001; stages 2-4, P c 0.0001; stages 3-4, P < O.OOl), whilst the lymphocyte numbers were significantly elevated at this stage (stages 3-4, P < 0.02). A marked decline in white blood cell numbers, to the lowest level in the pregnancy of chinchillas, was also observed before parturition (Gromadzka-Ostrowska et al., 1985). Generally, the lymphocytes in rabbit gestation were nearly in the same range as in human pregnancy (Pitkin and Witte, 1979). The decrease of leucocyte counts in our rabbits is probably the result of a reduction of the numbers of basophils and neutrophils. While the increase of neutrophils in human pregnancy probably resulted from the elevated levels of estrogen and corticosteroids (Pitkin and Witte, 1979) it is possible that these hormones do not have such marked effects on the stem cells of neutrophils in pregnant rabbits. The significant elevation of lymphocyte numbers in the last week of rabbit gestation (stages O-4, P -c0.0001; stages l-4, P < 0.0001; stages 2-4, P < 0.0001; stages 3-4, P < 0.05) would probablv be caused by an increase of the number of B 1ym;rhocytes. In contrast a slight decrease of total lymphocytes in primiparous cows was observed at parturition (Kashiwazaki et al., 1985). Whether there was also a change in the number of certain subpopulations of T lymphocytes in pregnant rabbits is still open to question. So, for example, the suppressor T lymphocytes (OKT 8 cells) (Hirahara et al., 1980; Cheney er al., 1984) as well as the percentage of OKT 4 cells (T helper cells) (Canepa et al., 1984), T lymphocytes which express for Fc-IgG (To cells) (Ong et al., 1983) and the number of T lymphocytes which carry trophoblastic glycoprotein-receptors (Sotnikova et al., 1985) were elevated during human pregnancy; but the total
482
K. KRIESTENet al.
number of T lymphocytes decreased in the course of human pregnancy (Knippel et al., 1984). The higher level of lymphocytes in our animal collective was presumably brought about by an increased number of B lymphocytes. The elevation of B lymphocytes in pregnant mice results mainly from the fetus itself (Newport and Carter 1983). On the other hand, T lymphocytes in rabbits could be important in the immune adaptation to pregnancy, they may play an essential role in embryo/fete-maternal immunological interaction. Because the embryo/fetus can be thought of as a tolerated semi-allograft, since one half of its MCH (major histocompatibility complex) antigens and/or other alloantigens are derived from the father and should be recognized by the mother as foreign (Beer and Billingham, 1974). It is possible that a depression of the cytolytic activity during gestation of rabbits may be due to the elevated level of progesterone (K. Kriesten et al., unpublished data) which presumably reduced the cell lysing capacity of T lymphocytes (effector cells) (Stites et al., 1983) and so is partially responsible for the tolerance of embryonal/fetal allografts in rabbits. In addition, alphafetoproteins, chorion gonadotrophin and placental lactogen in combination (Bischof et al., 1983) could also have inhibitory effects on lymphoblastogenesis of T cells in pregnant rabbits. Furthermore, uteroglobin in connection with transglutaminase (EC 2.3.2.13) should play a specific role in masking the antigenicity of the growing rabbit embryo during implantation (Murkherjee et al., 1982). The increase of monocytes in week 3 of gestation in our rabbits is comparable to the rise in that cell population within the second trimester in human pregnancy (Pitkin and Witte, 1979). It is not clear whether that cell population also has a reduced thromboblastin activity in pregnant rabbits (Oian et al., 1985). Monocytes of rabbits may also play a role in local activation of coagulation systems in pregnancy (especially in the utero-placental circulation). Monocytes could probably react with antibodies in the serum of pregnant rabbits, and this reaction could presumably provide a regulator signal for the suppression of T cell proliferation (Nieda et al., 1985). A marked increase of the monocyte/lymphocyte ratio was also observed in week 3 of gestation (Fig. I),
after this the ratio decreased. It is known that an excess of monocytes relative to the lymphocytes is even able to suppress some immune responses (Allison, 1978). Therefore, it can also be assumed, that a higher prostaglandin synthesis plays an essential role in these reactions (Kurland and Bockman, 1978). This probably represents a suppressive mechanism by which the allograft could be protected in rabbit gestation also. Whether the suppressor functions of monocytes and of some T cell subpopulations (mainly T helper cells) act in concert with other humoral factors (Stites et al., 1983) to protect the embryos/fetuses from rejection in rabbits, is still a field of speculation. In the blood of 28-day-old rabbit fetuses, the number of erythrocytes was about the half of that of the doe in week 4 of gestation (Table 4). The haemoglobin concentration was also relatively low compared to that of the mother at stage 4 of gestation. Whilst an increased mean erythrocyte volume (MCV) was noticed in 28-day-old fetuses, the Hb content of the solitary erthyrocytes (Hb,) was nearly the same as that of the doe. Similar values of mean corpuscular haemoglobin content (MCHC) were also found in rabbit fetuses and in the mothers. The haematocrit value was approximately one half of that of newborn rabbits (Harris et al., 1983) whilst the blood platelet count in the doe was nearly five times greater than that in the fetus. Whether at the same time, the width of platelets of the fetus was also changed, is still unsolved. A significantly lower leucocyte count was also found in the 28-day-old fetuses, compared with that of the mother at stage 4 (P < 0.0001). Lactation
The erythrocyte count showed a marked decrease in the 4 weeks of lactation which were monitored (stages 4-5, P <: 0.01; stages 4-6, P < 0.02; stages 4-7, P < 0.05) (Table 2). These findings could be connected with the loss of doe’s blood during and after parturition. Whilst a marked rise of erythrocyte number was observed in cows after parturition (Bostedt et al., 1974) the haematocrit values also diminished significantly after parturition in our rabbits (stages 45, P < 0.005; stages 4-6, P < 0.002; stages 4-7, P < 0.01; stages 4-8, P < 0.02) (Table 1). This is probably associated with a higher 0, release from haemoglobin to the tissue. At the same time the haematocrit values reached the nadir and were lower than those from pregnant as well as non-pregnant, Table 4. Haematological
gestation ’ lactation Fig. 1. Monocyte-lymphocyte ratios in gestation and lactation. The ratios were calculated as the mean of monocyte (%j over the mean of lvmohocvte Co?&)counts.
values of 28-day-old
fetuses
Blood values in maternal and fetal rabbit non-lactating animals. The haemoglobin concentration was also significantly lower in weeks 1 and 2 of lactation, in comparison with that during the gestation period (stages 4-5, P < 0.05; stages 4-6, P < 0.05). Against this, the haemoglobin content during human lactation rose steadily, apart from a slight decrease directly after parturition and was higher than in the course of pregnancy (Stirling et al., 1984). Also, the haemoglobin content in cows increased after parturition (Bostedt et al., 1974). In addition, the volume of erythrocytes in our rabbit collective further diminished in week 1 of this period (stages 4-5, P < 0.002) and showed an elevated level in the following weeks of lactation (stages 5-6, P ~0.01; stages 5-7, P < 0.001;stages 5-8, P < 0.002). Altogether the MCV was lower than the values of pregnant as well as non-pregnant, nonlactating animals. The decrease of the MCV in week 1 of lactation was in contrast with the results measured in mice (Miesel, 1978). The MCV of this species was immediately elevated after parturition. The MCV of sows was likewise markedly higher on day 10 of lactation and rose further from day 28 to day 35 during the course of lactation (Steinhardt et al., 1982). The values of mean corpuscular haemoglobin concentration (MCHC) was slightly higher during the early lactation period compared with that in the second half of gestation (Table l), whereas the haemoglobin content of solitary erythrocytes (Hb,) showed an unimportant decrease in comparison with the mean value of rabbits in week 4 of gestation. Moreover, the Hb, was lower than the values found in rabbits in the first half of gestation and also lower than those in non-pregnant, non-lactating animals (Table 1). The number of platelets in our animal collective reached a minimum in week 2 of lactation (stages 5-6, P < O.Ol), rose again in week 3 and dropped once more in week 4 (stages 5-8, P < 0.002) (Table 2). The number of these cells showed a higher trend during lactation compared to the last week of gestation. A rise in platelet counts was also measured in humans after delivery (Stirling et al., 1984). The number of leucocytes was significantly higher during lactation than during the course of gestatron (stages 4-5, P < 0.001; stages 4-6, P < 0.01; stages 4-7, P < 0.0001; stages 4-8, P < 0.001). Thereby, the leucocyte count showed a trough in week 2 of the lactation period (Table 2). The decrease of leucocytes was probably provoked by the diminished monocyte and eosinophil numbers at the time of lactation (stage 5-6, P < 0.001 resp. stages 5-6, P < 0.01) (Tables 2 and 3). The eosinophils showed a higher tendency during lactation compared with week 4 of gestation (Table 3). The peak level of this cell population could result from an allergic response to milk as conjectured for the cow (Brewer, 1957). However, the neutrophil cells of our rabbits showed similar values in the second week of lactation as during the gestation period and reached a maximum in week 4 of this period (stages 5-8, P < 0.001; stages 7-8, P < 0.0001) (Table 3). Whilst the basophil cell proportion was markedly elevated in week 1 of lactation, this cell population dropped in the following weeks of observation (stages 556, P < 0.05; stages 5-8, P < 0.01; stages 67 P < 0.01; stages 68, P < 0.001
483
stages 7-8, P < 0.01). The percentage of monocytes decreased significantly in week 1 of lactation (stages 4-5, P < 0.001) and was twice that of stage 5 in week 2 (Table 3) then increased to a maximum level in week 4 (stages 5-6, P < 0.01; stages 5-8, P < 0.01; stages 6-7, P < 0.01; stages 6-8, P < 0.01; stages 7-8, P < 0.001) whereas the lymphocytes were significantly lower during the lactation period compared with week 4 of gestation (stages 4-5, P < 0.0001; stages 4-6, P < 0.02; stages 4-8, P < 0.0001). This cell population reached a trough in week 4 of lactation (stages 5-8; P < 0.001; stages 68, P < 0.01; stages 7-8, P < 0.02). This suggests the possibility of a decreased maternal immune response in lactating rabbits as observed during the lactation of mice (Gamble and Ferguson, 1982) whilst a marked increase in the lymphocyte count in primiparous cows was noticed after parturition (Kashiwazaki et al., 1985). The monocyte-lymphocyte ratio reached a minimum in week 1 of lactation and rose slightly in week 2 (Fig. 1). Then the ratio decreased once more in the following week and showed a peak in week 4 of this period. This maximum appears to be related to an immunosuppresive mechanism. Whether the changes of neutrophils and lymphocytes in pregnant and lactating rabbits alone may be indicative of health or illness, must be examined by further investigations. However, heterophil cells and lymphocytes alone should show whether a rabbit is normal or ill (Hinton et al., 1982) as when all the blood cells were taken into account. SUMMARY
Haematological values of non-pregnant/nonlactating, pregnant as well as lactating rabbits (New Zealand White hybrid, N = IO) and of 28-day-old fetuses (N = 6) were measured. The erythrocyte count decreased in week 2 of pregnancy and was slightly elevated in the second half of this period. A marked decrease occurred in week 1 of lactation. The haemoglobin content dropped slightly in the second half of gestation and further decreased in week 1 of lactation. The haematocrit value showed only a slight decline during the gestation period, compared with the values of nonpregnant/non-lactating animals and was not significantly diminished in the lactation phase. The leucocyte count was lower during gestation compared to the values of non-pregnant/nonlactating animals. This cell population was slightly higher during the lactation period in comparison with that of the animals in week 4 of pregnancy. The platelet count showed a marked decrease in week 4 of gestation and reached a peak level in week 1 of the lactation phase. In 28-day-old fetuses, the erythrocyte count was very low, at 2.3 x lO”/l. The mean erythrocyte volume of the fetus was about 45% higher than that of the doe in week 4 of gestation. The haematocrit was nearly 21% lower than that of the mother animal at the end of pregnancy. The haemoglobin content was also relatively low in comparison to that of the doe. The leucocyte count was approximately one ninth that of the mother in week 4 of gestation. The platelet
K. KRIESTEN et al.
484 number mother
of the fetus
was
about
one fifth
that
of the
in week 4 of pregnancy.
Acknowledgements-The Renate Langer (MTLA) techniques.
authors wish to thank Miss for her help with haematological
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