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Effects of chronic hypoxia on hematocrit ratios and heart size in the pigeon
Vol . 9 Part I, Life Sciences Printed in Great Hrita~n
pp . 451-455, 1970 .
Pergamon Prese
1/ EFFECTS OF CHRONIC HYPOXIA ON HEMATOCRIT RATIOS AND HEART SIZE IN THE PIGEON James J . McGrath Division of Physiology, Department of Animal Sciences Rutgers University, New Brunswick, New Jersey (Received ? November 1989 ; in final form 27 January 1970) The effects of chronic altitude exposure on heart size and hematocrit ratios have been studied in numerous species .
How-
ever, the vast majority of the work has concerned itself with mammals while the avian species have received comparatively little attention . Barbashova (1) reported that birds and reptiles do not have a noticeable increase in the oxygen capacity of their blood during the process of adjusting to hypoxis .
However, Smith and
Abbott (2) and Burton and Smith (3) have shown increased hematocrit ratios end cardiac hypertrophy in chickens living at 12,500 feet elevation .
Dunson (4) also reported increased heart weights
as well as increased right and left lung weights in montane robins . Since Altland (5) had reported that pigeons are extremely resistant to acute altitude exposure, a study was undertaken to acclimatize pigeons to chronic hypoxia and to study changes which may occur in heart size, and hematocrit ratios with acclimatization . Materials and Methods Adult male homing pigeons were acclimatized to chronic hypoxia in a barometric chamber for 30 days . _1/
The chamber was
Supported in part by grants from USDA Project NE-61 and B.
Fortunato . 451
452
EFFECT OF CHRONIC HYPORIA
Vol. 9, No . 8
programmed for a simulated altitude of 22,000 feet and was represaurized to sea level every second day for 30 minutes for cleaning and food replenishment .
Control birds were maintained
in a similar chamber kept at sea level pressure, and were handled the same as the experimental animals .
At the end of the acclima-
tization period the birds were weighed and blood samples were drawn via the brachial vein for microhematocrit determinations . The birds were decapitated and the hearts were removed and trimmed of visible fat and weighed.
The stria were separated and the re-
mainder of the heart wee divided into 2 portions consisting of the right ventricle end the left ventricle and attached septum . These portions were then weighed separately on a Mettler balance . Results and Discussion Table 1 shows that the hematocrit ratios of the altitude birds were significantly greater than those of the control birds . After 30 days at 22,000 feet, hematocrit ratios were 75 .6 exposed birds as opposed to 59 .9 level .
in the
in birds maintained at sea
The difference between these values is significant at the
0.05 level .
The control values are within the range reported for
male birds by several authors as summarized by 3turkie (6) . The body mass and net heart data are presented in Table 2. There is no significant difference between the control and altitude birds in body weight, total heart weight, right ventricular weight or left ventricular plus septal mesa weights .
In a larger
sample, however, some of these differences might be significant. In Table 3 it can be seen that the ratio of the right ventricular mass to total heart mesa (RV/ST), as well ae the ratio of the right ventricular mass to the left ventricular and septal masses (RV/LV) is greater in the altitude exposed birds .
Tlie
RV/AT ratio was .0273 in the altitude birds, compared to .0207 in
Vol. 9, No. 8
EFFECT OF CHRONIC HYPOXIA
453
the control birds, whereas the RV/LV ratio wa$ .436 in the altitude birds compared to .329 in the control birds .
The differences
between the altitude and control birds in both these parameters are significant at the 0 .05 level . These results with pigeons, as well as the results of Dunaon (4) with robins and Burton and Smith (3) with chickens, indicate that birds do indeed develop a polycythemia and right ventricular hypertrophy in response to chronic altitude exposure .
Right ven-
tricular hypertrophy is a findirig common to many animals exposed to altitude, and is believed to be due to pulmonary arterial hypertension .
Pulmonary arterial blood preeaure was not measured
in these experiments, but numerous authors have reported increases in pulmonary blood pressure with altitude acclimatization (7) . Burton et al . (8) reported pulmonary arterial blood pressures doubled in chickens exposed to altitude compared to sea level controls . Thus, these studies clearly demonstrate that male pigeons also develop an increased hematocrit ratio, and a right ventricular hypertrophy in response to chronic hypoxic exposure .
The
first response results in an increased oxygen carrying capacity of the blood, while the second may reflect the increased work load imposed on the heart by pulmonary arterial hypertension,
Thus, it
is interesting that the pigeon, a bird very resistant to acute hypoxia (5), responds to chronic hypoxia in a manner similar to the chicken, a bird which is very susceptible to acute hypoxia . Summary Adult male pigeons were exposed to a simulated altitude of
22,000 feet for 30 days .
There were increases in the hematocrit
ratios, the right ventricular mass to total heart mass ratios, and right ventricular mesa to left ventricular mass ratios .
454
EFFECT OF CHRONIC HYPOXIA
Vol. 9, No . 8
These responses are similar to those seen in the chicken and in non-avian species, TABLE 1 Hematocrit ratios of control pigeons and pigeons exposed to 22,000 feet, Control No . of birds
Altitude
5
5
Mean (~)
56 .9
75 .6
s .E .
± .93
± 2 .3
3 ;. Difference between means significant at 0.05 level . Mann-Whitney II test used to test significance .
TABLE 2 Body (BW), Heart (HT ), Right Ventricular (RV) and Left Ventricular plus Septal (LV) mass weights of control pigeons and pigeons exposed to 22,000 feet . Control (5) Mean (grams)
Altitude (5) S .E .
Mean (grams)
S .E .
BW
263 .7
(±15 .7)
264 .7
(±16 .3)
HT
5 .172
(± .260)
4 .949
(± .014)
Lv
3 .274
(± .183)
3 .116
(± .206)
RV
1 .063
(t .029)
1 .362
(± .152)
Yol . 9, No. 8
LFFECT OF CHROMIC HYPOXIA
455
TABLE 3 Ratios of right
ventricular to total heart weights (RV/HT) and
right ventricular to left ventricular plue septal mass weights (RV/LV) of control pigeons and pigeons exposed to 22,000 feet . Control (5) RV/HT
RV/LV
Means
.0207
.329
S .E .
± .0013
1 .024
Altitude (5) RV/HT
RV/LV
.0273#
.436#
1 .0019
1 .033
Differences between control and altitude means significant at 0 .05 level . Mann-Whitney U test used to teat significance . References l.
Z. I . BARBASHOVA, Handbook of Ph siolopy, American Physiology Society, Washington, .
2.
A . H . 3MiTH and U. S. ABBOTT, foult . Sci . 1.0 :1459 (1961) .
3.
R . R. BURTON and A . H. SMITH, J. Appl . Physiol .
4.
W. A . .DUNSON, Condor
5"
P. D . ALTLAND, J . Appl . Physiol . 1:141 (1961) .
6.
P . D . STURKIE, Avian Physiology , Cornell Un~v . Press, Ithaca, New York (1965) .
7.
E. J . VAN LIERE and J. C . STICgNEY, Hypoxie, Univ . of Chicago Press, Chicago, Illinois (1963) .
8.
R . R . BURTON, E. L . BESCH and A . H . SMITH, Am . J . Physiol . 21 :1438 (1968) .
:782 (1967) .
:215 (1965) .
pp . 451-455, 1970 .
Pergamon Prese
1/ EFFECTS OF CHRONIC HYPOXIA ON HEMATOCRIT RATIOS AND HEART SIZE IN THE PIGEON James J . McGrath Division of Physiology, Department of Animal Sciences Rutgers University, New Brunswick, New Jersey (Received ? November 1989 ; in final form 27 January 1970) The effects of chronic altitude exposure on heart size and hematocrit ratios have been studied in numerous species .
How-
ever, the vast majority of the work has concerned itself with mammals while the avian species have received comparatively little attention . Barbashova (1) reported that birds and reptiles do not have a noticeable increase in the oxygen capacity of their blood during the process of adjusting to hypoxis .
However, Smith and
Abbott (2) and Burton and Smith (3) have shown increased hematocrit ratios end cardiac hypertrophy in chickens living at 12,500 feet elevation .
Dunson (4) also reported increased heart weights
as well as increased right and left lung weights in montane robins . Since Altland (5) had reported that pigeons are extremely resistant to acute altitude exposure, a study was undertaken to acclimatize pigeons to chronic hypoxia and to study changes which may occur in heart size, and hematocrit ratios with acclimatization . Materials and Methods Adult male homing pigeons were acclimatized to chronic hypoxia in a barometric chamber for 30 days . _1/
The chamber was
Supported in part by grants from USDA Project NE-61 and B.
Fortunato . 451
452
EFFECT OF CHRONIC HYPORIA
Vol. 9, No . 8
programmed for a simulated altitude of 22,000 feet and was represaurized to sea level every second day for 30 minutes for cleaning and food replenishment .
Control birds were maintained
in a similar chamber kept at sea level pressure, and were handled the same as the experimental animals .
At the end of the acclima-
tization period the birds were weighed and blood samples were drawn via the brachial vein for microhematocrit determinations . The birds were decapitated and the hearts were removed and trimmed of visible fat and weighed.
The stria were separated and the re-
mainder of the heart wee divided into 2 portions consisting of the right ventricle end the left ventricle and attached septum . These portions were then weighed separately on a Mettler balance . Results and Discussion Table 1 shows that the hematocrit ratios of the altitude birds were significantly greater than those of the control birds . After 30 days at 22,000 feet, hematocrit ratios were 75 .6 exposed birds as opposed to 59 .9 level .
in the
in birds maintained at sea
The difference between these values is significant at the
0.05 level .
The control values are within the range reported for
male birds by several authors as summarized by 3turkie (6) . The body mass and net heart data are presented in Table 2. There is no significant difference between the control and altitude birds in body weight, total heart weight, right ventricular weight or left ventricular plus septal mesa weights .
In a larger
sample, however, some of these differences might be significant. In Table 3 it can be seen that the ratio of the right ventricular mass to total heart mesa (RV/ST), as well ae the ratio of the right ventricular mass to the left ventricular and septal masses (RV/LV) is greater in the altitude exposed birds .
Tlie
RV/AT ratio was .0273 in the altitude birds, compared to .0207 in
Vol. 9, No. 8
EFFECT OF CHRONIC HYPOXIA
453
the control birds, whereas the RV/LV ratio wa$ .436 in the altitude birds compared to .329 in the control birds .
The differences
between the altitude and control birds in both these parameters are significant at the 0 .05 level . These results with pigeons, as well as the results of Dunaon (4) with robins and Burton and Smith (3) with chickens, indicate that birds do indeed develop a polycythemia and right ventricular hypertrophy in response to chronic altitude exposure .
Right ven-
tricular hypertrophy is a findirig common to many animals exposed to altitude, and is believed to be due to pulmonary arterial hypertension .
Pulmonary arterial blood preeaure was not measured
in these experiments, but numerous authors have reported increases in pulmonary blood pressure with altitude acclimatization (7) . Burton et al . (8) reported pulmonary arterial blood pressures doubled in chickens exposed to altitude compared to sea level controls . Thus, these studies clearly demonstrate that male pigeons also develop an increased hematocrit ratio, and a right ventricular hypertrophy in response to chronic hypoxic exposure .
The
first response results in an increased oxygen carrying capacity of the blood, while the second may reflect the increased work load imposed on the heart by pulmonary arterial hypertension,
Thus, it
is interesting that the pigeon, a bird very resistant to acute hypoxia (5), responds to chronic hypoxia in a manner similar to the chicken, a bird which is very susceptible to acute hypoxia . Summary Adult male pigeons were exposed to a simulated altitude of
22,000 feet for 30 days .
There were increases in the hematocrit
ratios, the right ventricular mass to total heart mass ratios, and right ventricular mesa to left ventricular mass ratios .
454
EFFECT OF CHRONIC HYPOXIA
Vol. 9, No . 8
These responses are similar to those seen in the chicken and in non-avian species, TABLE 1 Hematocrit ratios of control pigeons and pigeons exposed to 22,000 feet, Control No . of birds
Altitude
5
5
Mean (~)
56 .9
75 .6
s .E .
± .93
± 2 .3
3 ;. Difference between means significant at 0.05 level . Mann-Whitney II test used to test significance .
TABLE 2 Body (BW), Heart (HT ), Right Ventricular (RV) and Left Ventricular plus Septal (LV) mass weights of control pigeons and pigeons exposed to 22,000 feet . Control (5) Mean (grams)
Altitude (5) S .E .
Mean (grams)
S .E .
BW
263 .7
(±15 .7)
264 .7
(±16 .3)
HT
5 .172
(± .260)
4 .949
(± .014)
Lv
3 .274
(± .183)
3 .116
(± .206)
RV
1 .063
(t .029)
1 .362
(± .152)
Yol . 9, No. 8
LFFECT OF CHROMIC HYPOXIA
455
TABLE 3 Ratios of right
ventricular to total heart weights (RV/HT) and
right ventricular to left ventricular plue septal mass weights (RV/LV) of control pigeons and pigeons exposed to 22,000 feet . Control (5) RV/HT
RV/LV
Means
.0207
.329
S .E .
± .0013
1 .024
Altitude (5) RV/HT
RV/LV
.0273#
.436#
1 .0019
1 .033
Differences between control and altitude means significant at 0 .05 level . Mann-Whitney U test used to teat significance . References l.
Z. I . BARBASHOVA, Handbook of Ph siolopy, American Physiology Society, Washington, .
2.
A . H . 3MiTH and U. S. ABBOTT, foult . Sci . 1.0 :1459 (1961) .
3.
R . R. BURTON and A . H. SMITH, J. Appl . Physiol .
4.
W. A . .DUNSON, Condor
5"
P. D . ALTLAND, J . Appl . Physiol . 1:141 (1961) .
6.
P . D . STURKIE, Avian Physiology , Cornell Un~v . Press, Ithaca, New York (1965) .
7.
E. J . VAN LIERE and J. C . STICgNEY, Hypoxie, Univ . of Chicago Press, Chicago, Illinois (1963) .
8.
R . R . BURTON, E. L . BESCH and A . H . SMITH, Am . J . Physiol . 21 :1438 (1968) .
:782 (1967) .
:215 (1965) .