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Influence of donor and host age on the regeneration and blood flow of splenic transplants
Influence of Donor and Host Age on the Regeneration and Blood Flow of Splenic Transplants By J~rgen Westermann, Karl-Ulrich Willf6hr, and Reinhard Pabst Hannover, West Germany 9 After splenectomy there is an increased risk of fatal overwhelming postsplenectomy sepsis, especially in children. If all alternatives to splenectomy fail, autotransplantation of splenic fragments is indicated. These fragments regenerate after a necrotic phase to small splenic nodules. Regulatory factors governing the regeneration process are largely unknown. Inbred rats were used as a model to define the influence of recipient and donor age on the regenerated mass and the blood flow of transplanted splenic fragments. These are both important factors for the protective function of the spleen. Fetal, newborn, weanling, or adult spleens were implanted into the greater omentum of newborn, weanling, or adult rats. The younger the recipient and donor, the better the regeneration and perfusion of transplants. However, these did not reach more than 4 0 % of the normal splenic mass. In addition, no experimental group achieved more than one third of the normal splenic blood flow. There is an obvious age dependency in splenic regeneration and blood flow, but the transplants are far from attaining a normal splenic mass and perfusion. 9 1 9 8 8 by Grune & S t r a t t o n , Inc. INDEX WORDS: Splenic autotransplants.
and host age on the mass and blood flow of a splenic transplant. MATERIALS AND METHODS
A n i m a l s and Operation A total of 141 male Lewis rats were kept under barriermaintained conditions. All operations were carried out as previously described) Three to five thin slices of the excised spleen were implanted in a pouch formed in the greater omentum. The kinetics of regeneration was studied in adult rats in which 3, 6, 12, or 18 months after transplantation the regenerated nodules were carefully dissected out, blood flow having been measured and splenic tissue weighed. Sham-splenectomized rats served as controls. The general outline of the experiments concerning age of splenic donors is shown in Fig 1. Three groups of hosts were used for the transplants: newborn (two days), weanling (3 weeks), or adult rats (24 weeks). Donors of the implanted splenic tissue were fetal (15 days postconception), newborn, weanling, and adults. In most experiments the weight of the implanted splenic tissue was equivalent to 50% of the weight of the host's spleen that had been excised. In the case of fetal splenic tissue, smaller amounts were available and the neonatal hosts received ~4 mg, the weanlings and adults ~ 16 mg.
Blood Flow OR A L O N G T I M E the spleen was considered to be a useless organ that should be excised even after minor lacerations of the splenic capsule. In the last decade this attitude completely changed after the increased rate of fatal overwhelming postsplenectomy sepsis was documented for children and seemed likely for adults. 13 Today it is recommended that the traumatized spleen be preserved by application of hemostyptic agents, splenorrhaphy, or partial splenectomy. 2 Only if all these attempts fail is autotransplantation of splenic fragments into the greater omentum indicated. 2'3 However, the protective effect of regenerated splenic tissue could not be demonstrated in all studies, 4'5 and little is known about the effect of autotransplantation on the immune status. 6 Splenic transplants in experimental animals and man differ from a normal spleen in two major ways; the regenerated splenic mass is very small and blood flow is greatly reduced. 7 As both of these are essential factors for effective bacterial clearance, these parameters were tested in this study. In addition to gaining more insight into the mechanism of splenic regeneration, the clinical aspect of this study was to test whether the regenerative capacity of splenic tissue of a young child is better than that of an adult. Inbred rats were used as a model to define the influence of donor
F
Journal of Pediatric Surgery, Vol 23, No 9 (September),1988: pp 835-838
Blood flow was determined by the rubidium chloride technique (~30 ttCi rubidium chloride 86.) 9 Weighed samples of the spleen or splenic transplants, of both kidneys, and of the heart were used for 7 counting, and the total weight of the organs was determined. Radioactivity was expressed as counts per minute per milligram of organ weight. The mean and standard deviation were determined, and Student's t test was used to define significant differences. RESULTS
Duration o f Splenic Regeneration A f t e r Autotransplantation A n i m p o r t a n t c l i n i c a l q u e s t i o n is w h e t h e r a n d w h e n splenic regeneration ends. Therefore, weight and blood flow w e r e t e s t e d a t d i f f e r e n t t i m e s a f t e r t r a n s p l a n t a t i o n in a d u l t r a t s . A f t e r 3 m o n t h s , a m e a n o f o n l y 1 2 0 ___ 43 m g s p l e n i c t i s s u e w a s f o u n d , in c o n t r a s t t o t h e n o r m a l s p l e n i c w e i g h t o f 5 3 7 _+ 4 0 m g ( F i g 2 A ) . A t 6,
From the Centre of Anatomy, Medical School of Hannover, West Germany. Supported by the Deutsche Forschungsgemeinschaft, SFB 146, A5a. Address reprint requests to Dr J. Westermann, Zentrum Anatomie 4150, Medizinische Hochschule Hannover, Postf ach 610180, D-3000 Hannover 61, West Germany. 9 1988 by Grune & Stratton, Inc. 0022-3468/88/2309-0012503.00/0
835
836
WESTERMANN, WILLFOHR, AND PABST a g e of the donor
age of the donor fetal
newborn
weaniin9
~,,.
~
~_
'---]fetal
adult
NnewbornN
....
.o, lad~
~
*=p <0.05 300 "~
mg -
U
"E n:7
n=7
n=7
n=8
newborn
n.8
n.8
n.9
n.7
weanling
n~8
2oo-
(n 150"o
adult
1000J
age of the recipient
C OO> 50-
Fig 1. Schematic outline of the experimental protocol indicating d i f f e r e n t t y p e s o f d o n o r s and r e c i p i e n t s o f splenic t r a n s p l a n t s .
P
n:7
12, or as late as 18 months after transplantation, the regenerated splenic mass did not increase over the low 3-month value (Fig 2A). When blood flow to the transplant was expressed as a proportion of the cardiac output flowing through the splenic tissue, no significant differences were found between the transplanted groups from 3 to 18 months after transplantation (Fig 2B), Splenic blood flow in the adult transplants was 600 -
n:7
n:8
n=8
n:9
n=8
recipient weanling
n=7
n=8
recipient adult
Fig 3. Weight of regenerated splenic tissue 3 months after transplanting splenic particles from donor rats of different ages i n t o n e w b o r n , w e a n l i n g , o r a d u l t rats. S i g n i f i c a n t differences a r e also n o t e d (e).
always <1/6 of that of the normal spleen. Since no further splenic growth could be demonstrated after 3 months, this time frame was used in the following studies.
Effect of Donor and Host Age on the Regenerated Splenic Mass
s f- 4 0 0 9 O~
In newborn hosts, fetal and newborn splenic tissue regenerated equally well, but splenic tissue of adult rats resulted in significantly less regenerated tissue (Fig 3). When weanling rats were used as hosts, there
200 -
t-
n=7
recipient newborn
O. u)
a g e of the d o n o r n=40 control
A
n:8
n:6
n:12
n=6
3
6
12
18
~ - ~ fetal [ ]
newborn [ ]
. . . . Hng m
6000~,
4000-
ooo 3000-
0.3 -
0.2-
X ~
~*~
2000-
u
=
*:p(O.05
0.4-
0. = o .~-
adult
months after transplantation
|~ 3ooZ O.t-
--/--
j.I
~,~
I
200 100n=40
n=8
n=6
n=12
n=6
control
3
6
12
18
i n,7
months after transplantation
Fig 2. (A) Splenic weight and (B) blood flow in age-matched normal rats at 3, 6, 12, and 18 months after autotransplantation of splenic fragments in adult rats.
n,7
m ' ~ I n=7
n=8
n*8
nt8
n:9
n=7
recipient
recipient
recipient
newborn
weanling
adult
n=8
Fig 4. Weight of splenic transplants as a percentage of implanted splenic tissue 3 months prior. Significant differences a r e n o t e d (*).
REGENERATION OF SPLENIC TRANSPLANTS
837
was a significant decline in regenerated tissue from fetal via weanling to adult transplants. In adult hosts the fetal tissue did not regenerate as well as in younger ones, while splenic fragments from weanling rats resulted in more tissue than those from adult rats. For technical reasons, newborn and adult hosts could not be implanted with the same absolute weight of splenic donor tissue. Therefore, it was also important to compare the regenerated tissue as a percentage of the mass of implanted splenic tissue in the different groups. For all hosts the implanted fetal spleens showed a significantly better regeneration, which lessened the older the recipients were (Fig 4). A comparable relationship was obvious for newborn, weanling, and adult implanted tissue. Blood Flow Blood flow to the splenic transplants can be expressed in two ways: as flow per milligram of splenic tissue, and flow to all splenic tissue as a percentage of the cardiac output. There was no difference in flow rates to any transplants per milligram of splenic tissue. However, the different weights of the transplants resulted in a more complex picture (Fig 5). In twoday-old hosts, a significantly reduced percentage of cardiac output perfused the transplant received from an adult rat. The general pattern of blood flow is comparable to that of the absolute weights. Obviously, the greater the splenic weight the greater the percentage of cardiac output perfusing the transplants. It is necessary to stress that in no group of transplanted rats did blood flow reach more than one third of the normal a g e of the donor
[~fet., [ ~ .ewb*,. [ ~
. . . . ,i.g U
.d.,t
splenic blood flow. In the clinical situation, only splenic autotransplantation can be performed. Therefore, experimental groups receiving autotransplants are also worth comparing (Figs 3 and 5). There were no significant differences in splenic mass and blood flow, although the implanted mass varied from 15 _+ 1 mg in newborns and 47 _+ 3 mg in weanlings to 303 _+ 13 mg in adults. DISCUSSION
In experiments on partial splenectomy the protective function against experimental pneumococcal sepsis was proportional to the mass of splenic tissue, assuming a critical mass. ~~ To date only small splenic nodules have been seen using scintigraphy in patients after splenic autotransplantation. However, a decreasing clearance function has been described in 11 patients 2 to 4 years after splenic autotransplantation. 12 This study demonstrates that up to 18 months (about half of the life span of a rat) the transplants still had the same weight as after 3 months, when the transplantation was carried out in adult rats. Thus, there is no continuous increase in splenic weight with time, but about 20% of normal splenic weight seems to be the maximum. The clinical relevance of sufficient splenic mass is obvious from reports of fatal septicemia in at least 17 patients despite the presence of accessory spleens or regenerated splenic tissue. 7 Most transplants have been performed in adults. Disappointingly small amounts of regenerated splenic tissue should not result in false pessimism about the situation in children. This study shows that the younger the transplant recipient, the greater the amount of splenic tissue that was found later; this is in accordance with some earlier studies.!3J 4
~._
~, 0.14~ o
.=p,o.os ......
%.
7 o.~o. u
"~ o.os =
~ 0.06~ 0.04o ~o 0,02o
n=5
n=7
recipient newborn
n=7
n:6
n:8
recipient weanling
n:7
n=9
n=7
n:8
recipient adult
Fig 5. Blood flow as a percentage of cardiac o u t p u t t o regenerated splenic tissue in rats that had received transplants from donors of different ages 3 months before. Significant differences are also shown ( * ) .
.
.
.
.
.
.
.
.
.
.
Blood flow is another important factor for the clearance function of the spleen. 7'15 Blood flow per milligram of splenic transplants in relation to the flow to the kidney was not different between control spleens and most splenic transplants. However, in experiments with pigs the transplants were significantly less perf u s e d . 7'16 The protective function of the spleen depends more on the absolute blood flow or percentage of cardiac output passing the splenic filter system. No splenic transplant group exceeded one third of the normal splenic blood flow. In no experimental group did regenerated splenic mass attain more than 40% of that of control rats, or more than one third of the normal splenic blood flow. These facts should not lead to the wrong conclusion, ie, that more than 50% of the splenic tissue should be implanted, because this would probably create problems such as adhesions and massive necrosis, especially
838
WESTERMANN, WILLFUHR, AND PABST
in c h i l d r e n . T h e c o m p a r i s o n o f a u t o t r a n s p l a n t e d rats clearly demonstrated that although only 1/20 of the i m p l a n t e d m a s s o f a d u l t s was t r a n s p l a n t e d in n e w borns, s i m i l a r r e g e n e r a t e d splenic m a s s e s w e r e f o u n d 3 m o n t h s later. ACKNOWLEDGMENT
The authors thank Ms I. Dressend~rfer and Ms M. Peter for technical assistance, and Ms S. Fryk for assistance in preparing the manuscript. REFERENCES
1. Sekikawa T, Shatney CH: Septic sequelae after splenectomy for trauma in adults. Am J Surg 145:667-673, 1983 2. Cooper M J, Williamson RCN: Splenectomy: Indications, hazards and alternatives. Br J Surg 71:173-180, 1984 3. Witte MH, Witte CL, van Wyck DB, et al: Preservation of the spleen. Lymphology 16:128-137, 1983 4. Patel J, Williams JS, Naim JO, et al: Protection against pneumococcal sepsis in splenectomized rats by implantation of splenic tissue into an omental pouch. Surgery 91:638-641, 1982 5. Schwartz AD, Goldthorn JF, Winkelstein JA, et al: Lack of protective effect of autotransplanted splenic tissue to pneumococcal challenge. Blood 51:475-478, 1978 6. Westermann J, Pabst R: Autotransplantation of splenic fragments: Lymphocyte subsets in blood, lymph nodes and splenic tissue. Clin Exp Immunol 64:188-194, 1986
7. Pabst R, Kamran D: Autotransplantation of splenic tissue. J Pediatr Surg 21:120-124, 1986 8. Pabst R, Hafke R, Hillebrand J: Enhanced regeneration of transplanted splenic tissue by increased work load to the splenic compartments. J Trauma 25:326-328, 1985 9. Mendell PL, Hollenberg NK: Cardiac output distribution in the rat: Comparison of rubidium and microsphere methods. Am J Physio1221:1617-1620, 1971 10. van Wyck DB, Witte MH, Witte CL, et al: Critical splenic mass for survival from experimental pneumococcemia. J Surg Res 28:14-17, 1980 11. Bradshaw PH, Thomas CG: Partial splenectomy and overwhelming infection in rats. J Surg Res 32:173-175, 1982 12. Diirig M, Harder F: Auswirkungen der Splenektomie. Chirurg 57:189-193, 1986 13. Marine D, Manley OT: Homeotransplantation and autotransplantation of the spleen in rabbits. J Exp Med 32:113-130, 1920 14. Kovacs KF, Caride VJ, Touloukian R J: Regeneration of splenic autotransplants in suckling and adult rats. Arch Surg 116:335-336, 1981 15. Horton J, Ogden ME, Williams S, et al: The importance of splenic blood flow in clearing pneumococcal organisms. Ann Surg 195:172-176, 1982 16. Pimpl W, Thalhamer J, Pattermann M: Perfusion of autologous splenic grafts in correlation with specific immunological functions-An experimental study in pigs. Eur Surg Res 19:53-61, 1987
and host age on the mass and blood flow of a splenic transplant. MATERIALS AND METHODS
A n i m a l s and Operation A total of 141 male Lewis rats were kept under barriermaintained conditions. All operations were carried out as previously described) Three to five thin slices of the excised spleen were implanted in a pouch formed in the greater omentum. The kinetics of regeneration was studied in adult rats in which 3, 6, 12, or 18 months after transplantation the regenerated nodules were carefully dissected out, blood flow having been measured and splenic tissue weighed. Sham-splenectomized rats served as controls. The general outline of the experiments concerning age of splenic donors is shown in Fig 1. Three groups of hosts were used for the transplants: newborn (two days), weanling (3 weeks), or adult rats (24 weeks). Donors of the implanted splenic tissue were fetal (15 days postconception), newborn, weanling, and adults. In most experiments the weight of the implanted splenic tissue was equivalent to 50% of the weight of the host's spleen that had been excised. In the case of fetal splenic tissue, smaller amounts were available and the neonatal hosts received ~4 mg, the weanlings and adults ~ 16 mg.
Blood Flow OR A L O N G T I M E the spleen was considered to be a useless organ that should be excised even after minor lacerations of the splenic capsule. In the last decade this attitude completely changed after the increased rate of fatal overwhelming postsplenectomy sepsis was documented for children and seemed likely for adults. 13 Today it is recommended that the traumatized spleen be preserved by application of hemostyptic agents, splenorrhaphy, or partial splenectomy. 2 Only if all these attempts fail is autotransplantation of splenic fragments into the greater omentum indicated. 2'3 However, the protective effect of regenerated splenic tissue could not be demonstrated in all studies, 4'5 and little is known about the effect of autotransplantation on the immune status. 6 Splenic transplants in experimental animals and man differ from a normal spleen in two major ways; the regenerated splenic mass is very small and blood flow is greatly reduced. 7 As both of these are essential factors for effective bacterial clearance, these parameters were tested in this study. In addition to gaining more insight into the mechanism of splenic regeneration, the clinical aspect of this study was to test whether the regenerative capacity of splenic tissue of a young child is better than that of an adult. Inbred rats were used as a model to define the influence of donor
F
Journal of Pediatric Surgery, Vol 23, No 9 (September),1988: pp 835-838
Blood flow was determined by the rubidium chloride technique (~30 ttCi rubidium chloride 86.) 9 Weighed samples of the spleen or splenic transplants, of both kidneys, and of the heart were used for 7 counting, and the total weight of the organs was determined. Radioactivity was expressed as counts per minute per milligram of organ weight. The mean and standard deviation were determined, and Student's t test was used to define significant differences. RESULTS
Duration o f Splenic Regeneration A f t e r Autotransplantation A n i m p o r t a n t c l i n i c a l q u e s t i o n is w h e t h e r a n d w h e n splenic regeneration ends. Therefore, weight and blood flow w e r e t e s t e d a t d i f f e r e n t t i m e s a f t e r t r a n s p l a n t a t i o n in a d u l t r a t s . A f t e r 3 m o n t h s , a m e a n o f o n l y 1 2 0 ___ 43 m g s p l e n i c t i s s u e w a s f o u n d , in c o n t r a s t t o t h e n o r m a l s p l e n i c w e i g h t o f 5 3 7 _+ 4 0 m g ( F i g 2 A ) . A t 6,
From the Centre of Anatomy, Medical School of Hannover, West Germany. Supported by the Deutsche Forschungsgemeinschaft, SFB 146, A5a. Address reprint requests to Dr J. Westermann, Zentrum Anatomie 4150, Medizinische Hochschule Hannover, Postf ach 610180, D-3000 Hannover 61, West Germany. 9 1988 by Grune & Stratton, Inc. 0022-3468/88/2309-0012503.00/0
835
836
WESTERMANN, WILLFOHR, AND PABST a g e of the donor
age of the donor fetal
newborn
weaniin9
~,,.
~
~_
'---]fetal
adult
NnewbornN
....
.o, lad~
~
*=p <0.05 300 "~
mg -
U
"E n:7
n=7
n=7
n=8
newborn
n.8
n.8
n.9
n.7
weanling
n~8
2oo-
(n 150"o
adult
1000J
age of the recipient
C OO> 50-
Fig 1. Schematic outline of the experimental protocol indicating d i f f e r e n t t y p e s o f d o n o r s and r e c i p i e n t s o f splenic t r a n s p l a n t s .
P
n:7
12, or as late as 18 months after transplantation, the regenerated splenic mass did not increase over the low 3-month value (Fig 2A). When blood flow to the transplant was expressed as a proportion of the cardiac output flowing through the splenic tissue, no significant differences were found between the transplanted groups from 3 to 18 months after transplantation (Fig 2B), Splenic blood flow in the adult transplants was 600 -
n:7
n:8
n=8
n:9
n=8
recipient weanling
n=7
n=8
recipient adult
Fig 3. Weight of regenerated splenic tissue 3 months after transplanting splenic particles from donor rats of different ages i n t o n e w b o r n , w e a n l i n g , o r a d u l t rats. S i g n i f i c a n t differences a r e also n o t e d (e).
always <1/6 of that of the normal spleen. Since no further splenic growth could be demonstrated after 3 months, this time frame was used in the following studies.
Effect of Donor and Host Age on the Regenerated Splenic Mass
s f- 4 0 0 9 O~
In newborn hosts, fetal and newborn splenic tissue regenerated equally well, but splenic tissue of adult rats resulted in significantly less regenerated tissue (Fig 3). When weanling rats were used as hosts, there
200 -
t-
n=7
recipient newborn
O. u)
a g e of the d o n o r n=40 control
A
n:8
n:6
n:12
n=6
3
6
12
18
~ - ~ fetal [ ]
newborn [ ]
. . . . Hng m
6000~,
4000-
ooo 3000-
0.3 -
0.2-
X ~
~*~
2000-
u
=
*:p(O.05
0.4-
0. = o .~-
adult
months after transplantation
|~ 3ooZ O.t-
--/--
j.I
~,~
I
200 100n=40
n=8
n=6
n=12
n=6
control
3
6
12
18
i n,7
months after transplantation
Fig 2. (A) Splenic weight and (B) blood flow in age-matched normal rats at 3, 6, 12, and 18 months after autotransplantation of splenic fragments in adult rats.
n,7
m ' ~ I n=7
n=8
n*8
nt8
n:9
n=7
recipient
recipient
recipient
newborn
weanling
adult
n=8
Fig 4. Weight of splenic transplants as a percentage of implanted splenic tissue 3 months prior. Significant differences a r e n o t e d (*).
REGENERATION OF SPLENIC TRANSPLANTS
837
was a significant decline in regenerated tissue from fetal via weanling to adult transplants. In adult hosts the fetal tissue did not regenerate as well as in younger ones, while splenic fragments from weanling rats resulted in more tissue than those from adult rats. For technical reasons, newborn and adult hosts could not be implanted with the same absolute weight of splenic donor tissue. Therefore, it was also important to compare the regenerated tissue as a percentage of the mass of implanted splenic tissue in the different groups. For all hosts the implanted fetal spleens showed a significantly better regeneration, which lessened the older the recipients were (Fig 4). A comparable relationship was obvious for newborn, weanling, and adult implanted tissue. Blood Flow Blood flow to the splenic transplants can be expressed in two ways: as flow per milligram of splenic tissue, and flow to all splenic tissue as a percentage of the cardiac output. There was no difference in flow rates to any transplants per milligram of splenic tissue. However, the different weights of the transplants resulted in a more complex picture (Fig 5). In twoday-old hosts, a significantly reduced percentage of cardiac output perfused the transplant received from an adult rat. The general pattern of blood flow is comparable to that of the absolute weights. Obviously, the greater the splenic weight the greater the percentage of cardiac output perfusing the transplants. It is necessary to stress that in no group of transplanted rats did blood flow reach more than one third of the normal a g e of the donor
[~fet., [ ~ .ewb*,. [ ~
. . . . ,i.g U
.d.,t
splenic blood flow. In the clinical situation, only splenic autotransplantation can be performed. Therefore, experimental groups receiving autotransplants are also worth comparing (Figs 3 and 5). There were no significant differences in splenic mass and blood flow, although the implanted mass varied from 15 _+ 1 mg in newborns and 47 _+ 3 mg in weanlings to 303 _+ 13 mg in adults. DISCUSSION
In experiments on partial splenectomy the protective function against experimental pneumococcal sepsis was proportional to the mass of splenic tissue, assuming a critical mass. ~~ To date only small splenic nodules have been seen using scintigraphy in patients after splenic autotransplantation. However, a decreasing clearance function has been described in 11 patients 2 to 4 years after splenic autotransplantation. 12 This study demonstrates that up to 18 months (about half of the life span of a rat) the transplants still had the same weight as after 3 months, when the transplantation was carried out in adult rats. Thus, there is no continuous increase in splenic weight with time, but about 20% of normal splenic weight seems to be the maximum. The clinical relevance of sufficient splenic mass is obvious from reports of fatal septicemia in at least 17 patients despite the presence of accessory spleens or regenerated splenic tissue. 7 Most transplants have been performed in adults. Disappointingly small amounts of regenerated splenic tissue should not result in false pessimism about the situation in children. This study shows that the younger the transplant recipient, the greater the amount of splenic tissue that was found later; this is in accordance with some earlier studies.!3J 4
~._
~, 0.14~ o
.=p,o.os ......
%.
7 o.~o. u
"~ o.os =
~ 0.06~ 0.04o ~o 0,02o
n=5
n=7
recipient newborn
n=7
n:6
n:8
recipient weanling
n:7
n=9
n=7
n:8
recipient adult
Fig 5. Blood flow as a percentage of cardiac o u t p u t t o regenerated splenic tissue in rats that had received transplants from donors of different ages 3 months before. Significant differences are also shown ( * ) .
.
.
.
.
.
.
.
.
.
.
Blood flow is another important factor for the clearance function of the spleen. 7'15 Blood flow per milligram of splenic transplants in relation to the flow to the kidney was not different between control spleens and most splenic transplants. However, in experiments with pigs the transplants were significantly less perf u s e d . 7'16 The protective function of the spleen depends more on the absolute blood flow or percentage of cardiac output passing the splenic filter system. No splenic transplant group exceeded one third of the normal splenic blood flow. In no experimental group did regenerated splenic mass attain more than 40% of that of control rats, or more than one third of the normal splenic blood flow. These facts should not lead to the wrong conclusion, ie, that more than 50% of the splenic tissue should be implanted, because this would probably create problems such as adhesions and massive necrosis, especially
838
WESTERMANN, WILLFUHR, AND PABST
in c h i l d r e n . T h e c o m p a r i s o n o f a u t o t r a n s p l a n t e d rats clearly demonstrated that although only 1/20 of the i m p l a n t e d m a s s o f a d u l t s was t r a n s p l a n t e d in n e w borns, s i m i l a r r e g e n e r a t e d splenic m a s s e s w e r e f o u n d 3 m o n t h s later. ACKNOWLEDGMENT
The authors thank Ms I. Dressend~rfer and Ms M. Peter for technical assistance, and Ms S. Fryk for assistance in preparing the manuscript. REFERENCES
1. Sekikawa T, Shatney CH: Septic sequelae after splenectomy for trauma in adults. Am J Surg 145:667-673, 1983 2. Cooper M J, Williamson RCN: Splenectomy: Indications, hazards and alternatives. Br J Surg 71:173-180, 1984 3. Witte MH, Witte CL, van Wyck DB, et al: Preservation of the spleen. Lymphology 16:128-137, 1983 4. Patel J, Williams JS, Naim JO, et al: Protection against pneumococcal sepsis in splenectomized rats by implantation of splenic tissue into an omental pouch. Surgery 91:638-641, 1982 5. Schwartz AD, Goldthorn JF, Winkelstein JA, et al: Lack of protective effect of autotransplanted splenic tissue to pneumococcal challenge. Blood 51:475-478, 1978 6. Westermann J, Pabst R: Autotransplantation of splenic fragments: Lymphocyte subsets in blood, lymph nodes and splenic tissue. Clin Exp Immunol 64:188-194, 1986
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