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Effects of pharmacologic sympathectomy on gut hypertrophy in enterectomized rats
JOURNAL
OF SURGICAL
Effects
RESEARCH
19, 9-11 (1975)
of Pharmacologic Sympathectomy on Gut Hypertrophy in Enterectomized Rats ROBERT J. TOULOUKIAN, M.D., M. DAVID TILSON, M.D., AND ROBERT ROTH, Ph.D.
Departments of Surgery and Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06.510 Submitted for publication November 8, 1974
Blood flow, biochemical and histochem- 1 week after receiving the second intraical data indicate that the hypertrophied ileal venous dose of 6-hydroxydopamine. A comremnant is partially denervated of its parable group of normal animals was enterpostganglionic adrenergic fibers 2 months ectomized and served as controls. Enterecfollowing mid-enterectomy; the adrenergic tomized animals were weighed weekly and innervation of the nonhypertrophied jejunal their growth and activity observed. All aniremnant remains normal [7, 81. These mals were sacrificed 2 months following investigations established a coincidental but enterectomy, and histologic sections of the noncausal relationship between selective jejunal and ileal remnants were prepared for adrenergic denervation and gut hypertrophy. measurement of villus length. The technique The effects of pharmacologic sympa- of enterectomy and method for measuring thectomy with 6-hydroxydopamine on com- villus length and determining tissue catepensatory hypertrophy in the jejunal and cholamine concentration in the gut wall have ileal remnants following enterectomy was been described in previous communications studied to define further the relationship be- by the authors [5,7,8]. tween adrenergic innervation and gut RESULTS hypertrophy. Effective and continued pharmacologic METHODS AND MATERIALS sympathectomy was achieved in unoperated Pharmacologic sympathectomy was rats 1 week and 1 and 2 months after achieved in 15 Sprague-Dawley male rats receiving 6-hydroxydopamine, with catewith two tail-vein injections of 6- cholamine concentration in sections of hydroxydopamine (75 mg/kg) given at 7-day jejunum and ileum being reduced to about intervals. Five animals were sacrificed at 1 20% of normal (Fig. 1). Activity level and general appearance of week and at 1 and 2 months following the second dose of 6-hydroxydopamine. The enterectomized and non-operated rats effectiveness of adrenergic denervation was following pharmacologic sympathectomy determined by biochemical assay for cate- was not significantly different when comcholamine concentration in the jejunum and pared to their respective controls. An ileum and in a comparable group of un- analysis of the rate of growth by the method treated animals serving as control subjects. of least squares showed that there was a Measurements of jejunal and ileal villus linear relationship of weight with time for length were obtained in control and treated both groups (r = 0.96, P < O.OOl),and the animals 2 months after the initial dose of 6- rate of growth of enterectomized animals hydroxydopamine. with or without sympathectomy was not A second group of ten animals being pre- significantly different (Fig. 2). The villus pared by pharmacologic sympathectomy, as height of jejunum and ileum in unoperated described, underwent 50% mid-enterectomy and enterectomized animals was unaffected 9 Copyright o 1975 by Academic Press, Inc. All rights of reproduction in any form reserved.
10
JOURNAL OF SURGICAL
RESEARCH VOL. 19, NO. 1, JULY
JEJUNUM
1975
ILEUM
800 CATECHOLAMINE CONC. halqm dry weiqhtl
600
Cm t S.E.M.) 400
I
200
INI
ENTERECTDUI (2 mos)
t
IWk
Imo
Zmor
1
followlnq 6-OH oopa
FIG. 1. Catecholamine concentration in rat jejunum and ileum I week and 1 and 2 months following pharmacologic sympathectomy with 6-hydroxydopamine.
by pharmacologic sympathectomy (P < 0.005) (Table 1). DISCUSSION The role of the autonomic nervous system on controlling gut blood flow, cellular metabolism and compensatory growth has been extensively studied [l-8]. Blood flow to the mucosa of the ileal remnant is significantly elevated in rats 2 days after enterectomy; that the ileal remnant is also selectively
600
denervated of its adrenergic terminals was confirmed by evidence of reduced catecholamine concentration and fewer histofluorescent-staining adrenergic fibrils in the intestinal wall [7]. Vagotomy is known to reduce jejunal and ileal blood flow by nearly 50% in experimental subjects [3] and was believed responsible for villus shortening following vagotomy procedures [ 11. More recent reports contradict the initial studies and suggest that other metabolic or nutri-
corr coeff = 0.97
50% MIDENTERECTDMY
T T
450 I WT mean
400
T
T
(Kg) fS.E.M 350
250
200 1
I I
I 2
I 3
I 4
I 5
I 6
I 7
I 8
Weeks
FIG. 2. Growth of control and sympathectomized
rats following 50% mid-enterectomy.
TOULOUKIAN,
Villus Height’
AND
ROTH:
Operation
A B C D
None None Enterectomy Enterectomy
Sympathectomy None Yes Yes None
11
GUT HYPERTROPHY
TABLE 1 in Control and Enterectomized Rats 2 Months Following Sympathectomy with 6-Hydroxydopamine
Group
‘Villus
TILSON
Pharmacologic
Jejunum 60.2 61.4 82.4 82.8
f + f +
1.8 1.1 3.6 1.2
Ileum 44.6 46.4 63.6 64.7
f f + f
0.7 0.8 2.1 0.7
height, wm/lO * SEM.
tional factors are responsible for the observed histologic findings following vagot-
on-v PI.
6-Hydroxydopamine selectively destroys postganglionic sympathetic nerve endings and achieves an adequate and prolonged pharmacologic sympathectomy with longlasting depletion of tissue catecholamines by an impaired uptake of [3H] norepinephrine [9]. Chemically sympathectomized animals, therefore, serve as an excellent model for studying the effects of adrenergic denervation on the gut wall. The villus length of the jejunal and ileal remnants in enterectomized rats and the rate of growth of animals having pharmacologic sympathectomy did not significantly differ from control subjects in our experiments. The failure of sympathectomy to accelerate compensatory hypertrophy in the jejunal or ileal remnant of enterectomized subjects leaves unexplained the previously recognized association of reduced catecholamine stores in the hypertrophied remnant. It now appears, however, that this is a coincidental finding and not a critical causative factor in the mechanism responsible for compensatory villus hypertrophy. Further investigations of a “hormonal factor” [6] functioning independently of autonomic control is now justified in studying the genesis of gut hypertrophy. SUMMARY The effect of pharmacologic sympathectomy on compensatory hypertrophy and rate of growth of rats was studied 2 months after 50% mid-enterectomy. An 80% reduction in tissue catecholamine concentration
was achieved on biochemical assay of the jejunum and ileum 1 week and 1 and 2 months following administration of 6hydroxydopamine. No statistical difference in growth rate of the animals or villus height of the jejunal and ileal remnants was observed in the sympathectomized and control subjects. The evidence contradicts the hypothesis that adrenergic innervation initiates or accelerates hypertrophy in the gut remnant. REFERENCES 1. Ballinger, W. F., Iida, J., Aponte, G. E., Wirts, C. W., and Goldstein, F. Structure and function of the canine small intestine following total abdominal vagotomy. Surg. Gynecol. Obsrer. 118:1305, 1964. 2. Bejar, J., Broitman, S. A., and Zamcheck, N. Effect of vagotomy upon the small intestine. Gut 9:87, 1968. 3. Mackie, D. B., and Turner, M. D. The effect of truncal vagotomy on jejunal and ileal blood flow. J. Surg. Res. 11:356, 1971. 4. Padula, T. H., and Camishion, R. C. Mesenteric vascularity after vagotomy and splanchnicectomy. Surg. Gynecol. Obstet. 127:41, 1968. 5. Tilson, M. D., and Wright, H. K. Adaptation of functioning and bypassed segments of ileum during compensatory hypertrophy of the gut. Surgery 67~687, 1970. 6. Tilson, M. D., and Wright, H. K. Adaptational changes in the ileum following jejunectomy. In R. J. Goss (Ed.), Regulation of Organ and Tissue Growth. Academic Press, New York, 1972. 7. Touloukian, R. J., Aghajanian, G. K., and Roth, R. H. Adrenergic denervation of the hypertrophied gut remnant. Ann. Surg. 176:633, 1972. 8. Touloukian, R. J., and Spencer, R. P. Ileal blood flow preceding compensatory intestinal hypertrophy. Ann. Surg. 175:320, 1972. 9. Tranzer, J. P., and Thoenen, H. An electron microscopic study of selective, acute degeneration of sympathetic nerve terminals after administration of 6hydroxy dopamine. Experientia 24:155, 1968.
OF SURGICAL
Effects
RESEARCH
19, 9-11 (1975)
of Pharmacologic Sympathectomy on Gut Hypertrophy in Enterectomized Rats ROBERT J. TOULOUKIAN, M.D., M. DAVID TILSON, M.D., AND ROBERT ROTH, Ph.D.
Departments of Surgery and Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06.510 Submitted for publication November 8, 1974
Blood flow, biochemical and histochem- 1 week after receiving the second intraical data indicate that the hypertrophied ileal venous dose of 6-hydroxydopamine. A comremnant is partially denervated of its parable group of normal animals was enterpostganglionic adrenergic fibers 2 months ectomized and served as controls. Enterecfollowing mid-enterectomy; the adrenergic tomized animals were weighed weekly and innervation of the nonhypertrophied jejunal their growth and activity observed. All aniremnant remains normal [7, 81. These mals were sacrificed 2 months following investigations established a coincidental but enterectomy, and histologic sections of the noncausal relationship between selective jejunal and ileal remnants were prepared for adrenergic denervation and gut hypertrophy. measurement of villus length. The technique The effects of pharmacologic sympa- of enterectomy and method for measuring thectomy with 6-hydroxydopamine on com- villus length and determining tissue catepensatory hypertrophy in the jejunal and cholamine concentration in the gut wall have ileal remnants following enterectomy was been described in previous communications studied to define further the relationship be- by the authors [5,7,8]. tween adrenergic innervation and gut RESULTS hypertrophy. Effective and continued pharmacologic METHODS AND MATERIALS sympathectomy was achieved in unoperated Pharmacologic sympathectomy was rats 1 week and 1 and 2 months after achieved in 15 Sprague-Dawley male rats receiving 6-hydroxydopamine, with catewith two tail-vein injections of 6- cholamine concentration in sections of hydroxydopamine (75 mg/kg) given at 7-day jejunum and ileum being reduced to about intervals. Five animals were sacrificed at 1 20% of normal (Fig. 1). Activity level and general appearance of week and at 1 and 2 months following the second dose of 6-hydroxydopamine. The enterectomized and non-operated rats effectiveness of adrenergic denervation was following pharmacologic sympathectomy determined by biochemical assay for cate- was not significantly different when comcholamine concentration in the jejunum and pared to their respective controls. An ileum and in a comparable group of un- analysis of the rate of growth by the method treated animals serving as control subjects. of least squares showed that there was a Measurements of jejunal and ileal villus linear relationship of weight with time for length were obtained in control and treated both groups (r = 0.96, P < O.OOl),and the animals 2 months after the initial dose of 6- rate of growth of enterectomized animals hydroxydopamine. with or without sympathectomy was not A second group of ten animals being pre- significantly different (Fig. 2). The villus pared by pharmacologic sympathectomy, as height of jejunum and ileum in unoperated described, underwent 50% mid-enterectomy and enterectomized animals was unaffected 9 Copyright o 1975 by Academic Press, Inc. All rights of reproduction in any form reserved.
10
JOURNAL OF SURGICAL
RESEARCH VOL. 19, NO. 1, JULY
JEJUNUM
1975
ILEUM
800 CATECHOLAMINE CONC. halqm dry weiqhtl
600
Cm t S.E.M.) 400
I
200
INI
ENTERECTDUI (2 mos)
t
IWk
Imo
Zmor
1
followlnq 6-OH oopa
FIG. 1. Catecholamine concentration in rat jejunum and ileum I week and 1 and 2 months following pharmacologic sympathectomy with 6-hydroxydopamine.
by pharmacologic sympathectomy (P < 0.005) (Table 1). DISCUSSION The role of the autonomic nervous system on controlling gut blood flow, cellular metabolism and compensatory growth has been extensively studied [l-8]. Blood flow to the mucosa of the ileal remnant is significantly elevated in rats 2 days after enterectomy; that the ileal remnant is also selectively
600
denervated of its adrenergic terminals was confirmed by evidence of reduced catecholamine concentration and fewer histofluorescent-staining adrenergic fibrils in the intestinal wall [7]. Vagotomy is known to reduce jejunal and ileal blood flow by nearly 50% in experimental subjects [3] and was believed responsible for villus shortening following vagotomy procedures [ 11. More recent reports contradict the initial studies and suggest that other metabolic or nutri-
corr coeff = 0.97
50% MIDENTERECTDMY
T T
450 I WT mean
400
T
T
(Kg) fS.E.M 350
250
200 1
I I
I 2
I 3
I 4
I 5
I 6
I 7
I 8
Weeks
FIG. 2. Growth of control and sympathectomized
rats following 50% mid-enterectomy.
TOULOUKIAN,
Villus Height’
AND
ROTH:
Operation
A B C D
None None Enterectomy Enterectomy
Sympathectomy None Yes Yes None
11
GUT HYPERTROPHY
TABLE 1 in Control and Enterectomized Rats 2 Months Following Sympathectomy with 6-Hydroxydopamine
Group
‘Villus
TILSON
Pharmacologic
Jejunum 60.2 61.4 82.4 82.8
f + f +
1.8 1.1 3.6 1.2
Ileum 44.6 46.4 63.6 64.7
f f + f
0.7 0.8 2.1 0.7
height, wm/lO * SEM.
tional factors are responsible for the observed histologic findings following vagot-
on-v PI.
6-Hydroxydopamine selectively destroys postganglionic sympathetic nerve endings and achieves an adequate and prolonged pharmacologic sympathectomy with longlasting depletion of tissue catecholamines by an impaired uptake of [3H] norepinephrine [9]. Chemically sympathectomized animals, therefore, serve as an excellent model for studying the effects of adrenergic denervation on the gut wall. The villus length of the jejunal and ileal remnants in enterectomized rats and the rate of growth of animals having pharmacologic sympathectomy did not significantly differ from control subjects in our experiments. The failure of sympathectomy to accelerate compensatory hypertrophy in the jejunal or ileal remnant of enterectomized subjects leaves unexplained the previously recognized association of reduced catecholamine stores in the hypertrophied remnant. It now appears, however, that this is a coincidental finding and not a critical causative factor in the mechanism responsible for compensatory villus hypertrophy. Further investigations of a “hormonal factor” [6] functioning independently of autonomic control is now justified in studying the genesis of gut hypertrophy. SUMMARY The effect of pharmacologic sympathectomy on compensatory hypertrophy and rate of growth of rats was studied 2 months after 50% mid-enterectomy. An 80% reduction in tissue catecholamine concentration
was achieved on biochemical assay of the jejunum and ileum 1 week and 1 and 2 months following administration of 6hydroxydopamine. No statistical difference in growth rate of the animals or villus height of the jejunal and ileal remnants was observed in the sympathectomized and control subjects. The evidence contradicts the hypothesis that adrenergic innervation initiates or accelerates hypertrophy in the gut remnant. REFERENCES 1. Ballinger, W. F., Iida, J., Aponte, G. E., Wirts, C. W., and Goldstein, F. Structure and function of the canine small intestine following total abdominal vagotomy. Surg. Gynecol. Obsrer. 118:1305, 1964. 2. Bejar, J., Broitman, S. A., and Zamcheck, N. Effect of vagotomy upon the small intestine. Gut 9:87, 1968. 3. Mackie, D. B., and Turner, M. D. The effect of truncal vagotomy on jejunal and ileal blood flow. J. Surg. Res. 11:356, 1971. 4. Padula, T. H., and Camishion, R. C. Mesenteric vascularity after vagotomy and splanchnicectomy. Surg. Gynecol. Obstet. 127:41, 1968. 5. Tilson, M. D., and Wright, H. K. Adaptation of functioning and bypassed segments of ileum during compensatory hypertrophy of the gut. Surgery 67~687, 1970. 6. Tilson, M. D., and Wright, H. K. Adaptational changes in the ileum following jejunectomy. In R. J. Goss (Ed.), Regulation of Organ and Tissue Growth. Academic Press, New York, 1972. 7. Touloukian, R. J., Aghajanian, G. K., and Roth, R. H. Adrenergic denervation of the hypertrophied gut remnant. Ann. Surg. 176:633, 1972. 8. Touloukian, R. J., and Spencer, R. P. Ileal blood flow preceding compensatory intestinal hypertrophy. Ann. Surg. 175:320, 1972. 9. Tranzer, J. P., and Thoenen, H. An electron microscopic study of selective, acute degeneration of sympathetic nerve terminals after administration of 6hydroxy dopamine. Experientia 24:155, 1968.