Compensatory-adaptive modifications of the C-cell apparatus of the thyroid in normal rats of various ages and in partial sympathectomy

Population of the thyroid C-cells, normal and at sympathectomy has been analyzed in 75 white male rats at the age of 1, 3 and 6 months by means of electron microscopical, morphometrical and radioimmunological methods. Partial sympathectomy has been performed using subcutaneous injection of guanethidine (15 mg/kg of body mass) during 14 days after birth. During the period from 1 up to 6 months of life in intact rats a decrease in C-cells functional activity is observed. Under conditions of sympathectomy in 30-day-old animals decreasing extrusion processes of the secretory material are observed. During successive periods of life (3 and 6 months) mechanisms of paracrinic evacuation of hormonal products enhance considerably, nuclear volume of the cells and number of C-cells in the field of vision increase. Their hyperplastic alterations in the sympathectomized thyroid gland are more pronounced in 3-month-old animals.     

Brain enzyme activity in irradiated sympathectomized rats

The results are reviewed from studies of activity of hexokinase (2.7.1.1.EC), dehydrogenase glucose-6-phosphate (1.1.1.49 EC), and cholinesterase (3.1.1.7 EC) in subcellular fractions of rat brain at the background of chemical sympathectomy induced by long-term administration of guanethidine and subsequent irradiation with a dose of 7 Gy. In conditions of sympathectomy, the enzyme activity is inhibited; in irradiated sympathectomized rats, activity of hexokinase and cholinesterase increases to reach the level of that of intact animals while dehydrogenase remains inhibited.     

Effect of guanethidine-induced sympathectomy on osteoblastic activity in the rat femur evaluated by 3H-proline autoradiography

Osteoblastic activity in the rat femur was assessed following sympathectomy by injections of guanethidine sulfate from birth to 14 days of age. At ages 30, 45 and 90 days, osteogenesis was monitored by quantitative autoradiography using 3H-proline. Grain counts over periosteal osteoblasts of the femoral diaphysis showed a significant reduction in the uptake of 3H-proline in sympathectomized rats. The results indicate that the sympathetic innervation of bone influences osteoblastic activity and provide support for a role of the autonomic nervous system in the regulation of bone formation.     

Characteristics of the recovery processes in the resected thyroid of adult rats after sympathectomy

The investigation was carried out on 65 adult white male rats (12-month-old) after normal development or chemical sympathectomy by guanethidine and subtotal thyroidectomy. By means of electronic microscopic, autoradiographic and radioimmunological methods the increased functional activity in thyroid gland of chemically sympathectomized rats was found. This is mainly due to thyrotropin hyperproduction and intensification of proliferative potential of the organ. Partial resection of sympathectomized rats thyroid gland leads to exhaustion of adenohypophysis compensatory potential manifested in disjunction of integrative connections in hypothalamus-hypophysis-thyroid gland system and delay of thyroid status normalization.     

Effects of dosed sympathectomy on the development of adaptation-compensation reaction of C-cells of the thyroid gland and chromaffin cells of the adrenal glands in young rats

Using radioimmunological, morphometrical, electron microscopic and luminescent methods, comparative analysis of thyroid C-cells and adrenal chromaffin cells has been carried out at guanethidine sympathectomy in young rats. Significant decrease of functional activity of C-cells with concomitant hyperplasia of C-cells population under blockade of sympathetic influences has been revealed. Compared to C-cells, adrenal chromaffinocytes of sympathectomized rats possess higher degree of structural-functional mobilization and are characterized by intensive secretion of catecholamines directed at restoration of tissue neurotransmitter deficit.     

Autoradiographic assessment of 3H-proline uptake by osteoblasts following guanethidine-induced sympathectomy in the rat

Summary Sympathectomy was carried out in rats by injections of guanethidine-sulfate from birth to 14 days of age. At 45 days of age, the activity of osteoblastic cells was monitored by ³H-proline autoradiography. Effectiveness of sympathectomy was verified by light-microscopic examination of superior cervical and celiac ganglia. Grain counts over periosteal osteoblasts of the femoral diaphysis and osteoblasts mesial to the first molar in the mandible demonstrated a significantly reduced uptake of ³H-proline in the sympathectomized rats. The data provide direct evidence of sympathetic influence on osteoblastic activity and suggest that sympathectomy may result in the loss of a trophic influence which is important in the regulation of osteogenesis.Supported by N.I.D.R. grant DEO 4557 (R.M.K.), N.I.H. grant 5-SO1RR-5373 to K.U.M.C., and N.I.H. grant RR-05332 to N.Y.U. (U.S.). We thank Charles A. Brownley of CIBA-Geigy, Summit, N.J. for the guanethidine sulfate     

Neonatal chemical sympathectomy attenuates fructose-induced hypertriglyceridemia and hypertension in rats

Experiments were performed to determine the pathogenic contribution of the peripheral sympathetic nervous system to fructose-induced hypertriglyceridemia, hyperinsulinemia and hypertension in rats. Neonatal chemical sympathectomy was performed in neonatal Sprague-Dawley rats (1-week old) by administration of guanethidine (50 microg/g, i.p.) 5 times per week for consecutive 3 weeks and nerve-intact rats were served as controls. Both groups of rats were fed a fructose-enriched diet for 9 weeks. The systolic blood pressure (SBP) and body weight were measured weekly and arterial blood samples were taken weekly for determinations of plasma insulin, glucose and triglyceride levels. The results showed that fructose feeding for one week significantly increased SBP in intact rats and sympathectomized rats (116+/-1 to 119+/-1 mmHg and 116+/-1 to 120+/-1 mmHg, respectively). SBP further increased thereafter in both groups. However, the increased SBP levels were significantly higher in intact group than in sympathectomized group after 5 weeks of fructose feeding. Fructose feeding for one week concurrently produced hypertriglyceridemia that preceded the appearance of hyperinsulinemia in both groups. The elevated plasma triglyceride levels were significantly lower in sympathectomized rats than in intact rats after 3 weeks of fructose feeding, whereas the elevated plasma insulin concentrations were not different between groups throughout fructose feeding period. Plasma glucose concentrations of both groups were comparable and remained unchanged throughout the study. These data indicate that neonatal chemical sympathectomy attenuated, but did not prevent, fructose-induced elevations in blood pressure and plasma triglyceride levels, suggesting a partial dependency of fructose-induced hypertriglyceridemia and hypertension on the integrity of the peripheral sympathetic nervous system (SNS) in rats.     

Ovarian sympathectomy in the guinea pig

Summary The role of ovarian adrenergic nerves in follicular growth was studied in prepubertal guinea pigs by determining the effect of sympathectomy on 1) follicle populations and 2) follicular development following exogenous gonadotropin administration. Selective unilateral ovarian sympathectomy was achieved by injecting 6-hydroxydopamine into a surgically closed periovarian bursa on day 20 postpartum. The contralateral surgically closed ovarian bursa was injected with the vehicle used for 6-hydroxydopamine. On day 25, animals were injected with pregnant mare serum or saline followed by human chorionic gonadotropin or saline 48 h later. All animals were laparotomized on day 28 and blood from utero-ovarian veins was collected bilaterally for androstenedione determination. Ovaries were processed for morphometric analysis of follicles. The sympathectomized ovary in saline-injected animals had a significant decrease in preantral follicles (characterized by 2 layers of granulosa cells without antrum formation), an increase in 310–500 m diameter atretic follicles and an increase in follicles 700 um compared to the contralateral control ovary. There were no differences in androstenedione levels from the two sides, ovarian weights or the total number of follicles per ovary. Neither ovary had corpora lutea. The sympathectomized ovary in animals injected with gonadotropins was not different from the contralateral ovary in any of the parameters measured. Both control and sympathectomized ovaries had newly formed corpora lutea in response to the exogenous gonadotropins. These results suggest that ovarian adrenergic nerves normally participate in follicular development in the prepubertal guinea pig. However, exogenous gonadotropins may override neural influences on the prepubertal ovary.     

Effect of sympathectomy on the phenotype of smooth muscle cells of middle cerebral and ear arteries of hyperlipidaemic rabbits

This study was carried out to determine whether sympathectomy influences the phenotypic modulation of smooth muscle cells in the peripheral and cerebral arteries of heritable hyperlipidaemic rabbits. Unilateral superior cervical ganglionectomy (common origin of innervation to the middle cerebral artery and the central ear artery) was performed on four Watanabe heritable hyperlipidaemic rabbits. Cross-sections of the ipsi- (sympathectomized) and the contralateral (intact) cerebral and ear arteries were prepared 2 months later and labelled with monoclonal antibodies against vimentin and desmin, two markers of the differentiation of smooth muscle cells, and α-smooth muscle actin, a marker of these cells. Sections from control and sympathectomized arteries were analysed with a confocal laser scanning microscope. Compared with contralateral intact ear arteries, the sympathectomized ear artery developed a thickened intima with dedifferentiated smooth muscle cells, expressing α-smooth muscle actin but no desmin, whereas the middle cerebral artery remained unchanged. These results suggest that sympathectomy may favour the progression of atherosclerosis in peripheral but not in cerebral arteries of Watanabe heritable hyperlipidaemic rabbits     

Electrophysiological effects of ouabain in 6-hydroxydopamine pretreated dogs

Chemical sympathectomy and bilateral vagotomy were used to evaluate the contribution of each division of the autonomic nervous system in the electrophysiological actions of ouabain. Intact and chemically sympathectomized dogs were given successive and cumulative doses of ouabain until toxicity became manifest (ventricular extrasystoles and (or) ventricular tachycardia). An additional group of normal and sympathectomized animals was also submitted to bilateral vagotomy in the presence of a therapeutic dose of ouabain. Sinus cycle length, AH interval of the His bundle electrogram, atrioventricular junctional effective and functional refractory periods were increased by ouabain at therapeutic doses. These effects were no different in sympathectomized dogs than in intact dogs, indicating the absence of any significant contribution of efferent sympathetic neural activity. However, our results suggested that vagal enhancement was the main mechanism whereby ouabain produced sinus bradycardia and depression of atrioventricular conduction. Sympathectomy with 6-OHDA did not modify nor abolish ouabain toxicity. However, toxic doses were significantly higher in sympathectomized animals than in normal animals. Considering that increasing heart rate by cardiac pacing or vagotomy significantly lowered toxic doses of ouabain in both intact and sympathectomized dogs, it is possible that sympathectomy could influence ouabain toxicity by altering heart rate alone.     

Ethanol-induced cardiac hypertrophy: effects of peripheral sympathectomy

The development of cardiac hypertrophy was examined in rats that had undergone sympathectomy with 6-hydroxydopamine. After 4 days, the rats were given severely intoxicating doses of ethanol or isocalorically paired quantities of maltose-dextrin by intubation at 8-h intervals up to 48 h. The ethanol and sugar intubations were applied in a nutritionally adequate, liquid diet mix. The extent of the peripheral sympathectomy was evident from the absence of detectable quantities of noradrenaline in hearts of animals injected with the neurotoxin and in the reduced levels of excreted noradrenaline. The adrenal medullary catecholamine contents of sympathectomized rats were unchanged in the absence of ethanol; there were reduced quantities of adrenaline in the medullae of rats given ethanol. The adrenal glands of rats given ethanol were larger than those from control animals. Urine samples from sympathectomized and control rats, given ethanol, displayed equivalent increases in excreted adrenaline and noradrenaline. Increases in relative cardiac weight were evident in hearts from sympathectomized animals after 4 days of sympathectomy, and this change reached significance in the hearts from 6-hydroxydopamine-treated rats after a further 2 days on the control diet. Hearts from animals exposed to ethanol showed a marked, rapid development of cardiomegaly; after 24 h there was an increased mass of some 17%, which was sustained over the remaining 24-h period. The proportion of cardiac protein did not differ in the large hearts from ethanol-treated animals and those from their controls, hence myocardial oedema could not account for the increase in weight.(ABSTRACT TRUNCATED AT 250 WORDS)     

Acute renal function in chronically sympathectomized deoxycorticosterone acetate-treated miniature swine

We recently validated a swine model in which chronic treatment with 6-hydroxydopamine (6-OHDA) produced an effective sympathectomy. These sympathectomized swine demonstrated a significantly attenuated hypertensive response when treated with deoxycorticosterone acetate (DOCA). Because renal nerve activity is elevated and important in controlling renal function and blood pressure in the DOCA swine model, we wanted to study the effect of chronic sympathectomy on acute renal hemodynamics and tubular function. Kidney function was assessed in 14 DOCA-treated miniature swine, 8 of which were sympathectomized by chronic treatment with 6-OHDA, while 6 served as controls. Effective renal sympathectomy in this model has been previously confirmed by a significant reduction (97%) of norepinephrine in renal cortical tissue. When anesthetized, mean arterial pressure and renal blood flow were similar between the two groups. Glomerular filtration rate was lower by 43%, urine flow rate by 71%, sodium excretion by 66%, and potassium excretion by 48% in the 6-OHDA DOCA animals. All of these parameters were significantly different from the intact DOCA controls. These results indicate that anesthetized, chronically sympathectomized swine exhibit decreased renal excretory function. The changes in renal function may have been due to the development of a tubular or glomerular supersensitivity to circulating antinatriuretic factors, since the 6-OHDA group had a 28% greater pressor response to the alpha-agonist phenylephrine and a significantly greater fall in mean arterial pressure in response to alpha-blockade with prazosin when compared with the controls. These changes in renal function may also explain why the 6-OHDA animals demonstrated a slight increase in mean arterial pressure in response to DOCA. Because acute renal denervation in DOCA-treated swine produces a diuresis and natriuresis, this study affirms that there may be important functional differences in acutely versus chronically denervated kidneys for which the implications under normal physiologic conditions are unknown.     

Calcitonin gene-related peptide and substance P contribute to reduced blood pressure in sympathectomized rats

CGRP and substance P (SP) are produced in dorsal root ganglia (DRG) sensory neurons and modulate vascular tone. Sympathetic and sensory nerves compete for NGF, a potent stimulator of CGRP and SP, and it has been suggested that sympathetic hyperinnervation in spontaneously hypertensive rats may reduce the availability of NGF to sensory nerves, thus reducing CGRP and SP. The purpose of this study was to determine whether destruction of peripheral sympathetic nerves in normal rats would increase the availability of NGF for sensory neurons and enhance expression of CGRP and SP. Sympathectomy was produced in rats by guanethidine sulfate administration. Control rats received saline. Sympathectomized rats displayed reductions in blood pressure (BP) and atria norepinephrine levels, whereas NGF levels in the DRG, spleen, and ventricles were increased. Sympathectomy also enhanced CGRP and SP mRNA and peptide content in DRG. Administration of CGRP and SP receptor antagonists increased the BP in sympathectomized rats but not in the controls. Thus sympathectomy enhances sensory neuron CGRP and SP expression that contributes to the BP reduction.     

Characteristics of the secretory activity of the respiratory cells of mouse lungs after partial chemical sympathectomy

Partial "sympathectomy" in the neonatal BALB mice was achieved by the treatment with guanethidine. The number of neurons in the stellate ganglion decreased to 20% of the control values and remained constant throughout the subsequent period of 1 month. Partial "chemical sympathectomy" did not affect the postnatal growth and development of the lungs. Partial "chemical sympathectomy" significantly increased the number of secreting cells in bronchiolar and alveolar regions. Secretory activity of the alveolocyte population, type two, synthetizing and secreting surfactant also increased. It has been concluded that the partial "chemical sympathectomy" stimulated the alveolar surfactant secretion.     

Histochemical evidence of chemical sympathectomy by guanethidine in newborn rats

Synopsis Guanethidine is known to cause a loss of catecholamines from sympathetically innervated tissues and sympathetic ganglia in adult animals but its effect on newborn animals has not been examined.Newborn rats were injected daily with guanethidine (20 mg/kg body weight) for 8 days. They were killed when 1 month-old along with untreated litter mate controls. Catecholamines were demonstrated in the iris, in the pineal body and in sympathetic ganglia, using the formaldehyde-induced fluorescence method.In the guanethidine-treated rats there was a complete loss of fluorescent nerve fibres from the pineal body and an almost complete loss of similar fibres from the iris. The sympathetic ganglia were reduced to less than 10% of the control ganglia, and the number of nerve cell bodies per unit area was decreased in the ganglion remnants.It is concluded that guanethidine causes, in newborn rats, an irreversible destruction of most sympathetic neurons, i.e. a chemical sympathectomy closely resembling that obtainable in newborn animals by injections of 6-hydroxydopamine or antiserum to nerve growth factor.     

Developmental delay of lingual lipase expression after guanethidine-induced sympathectomy.

Rat lingual lipase increases during postnatal development. To evaluate the role of the sympathetic nervous system in the control of lingual lipase during development, suckling rats were chemically sympathectomized by chronic treatment with guanethidine. This treatment was found to be effective in suppressing the developmental increase of lingual lipase. The effect was age dependent and also related to the dose of guanethidine given (i.e., the higher the dose, the more effective the suppression is, up to 40 micrograms/g body wt). The effect of guanethidine on lingual lipase suppression was not a result of induced stress, since simultaneous treatment with RU-38486, a known glucocorticoid receptor antagonist, did not prevent the decrease in lingual lipase activity. Ephedrine, a known sympathomimetic agent, restored the lingual lipase to a near normal level in guanethidine-treated animals, confirming that guanethidine acts through the sympathetic nerves. Furthermore, histochemical studies showed that guanethidine-treatment resulted in the reduction or elimination of catecholaminergic fibers in the von Ebner's glands. The effect of guanethidine was found to be transient, in that the lingual lipase activity showed complete recovery upon withdrawal of the treatment for 1 week. Together, the results indicated that sympathetic nerves have an important regulatory role in lingual lipase in rat pups during development.     

Adrenal lipid profiles of chemically sympathectomized normoxic and hypoxic neonatal rats.

Neonatal hypoxia is a common condition that elicits a coordinated endocrine response. In the neonatal rat, hypoxia induces an ACTH-independent increase in corticosterone which can be partially blocked by chemical sympathectomy. The present study sought to characterize the effects of sympathectomy on the adrenal lipid profile, since previous work suggested that augmented plasma corticosterone during hypoxia may be due to changes in adrenal lipid metabolism. Newborn rats were exposed to normoxia or hypoxia from birth to seven days of age, and guanethidine was used to produce the sympathectomy. Plasma epinephrine and norepinephrine were not significantly affected by hypoxia, while guanethidine decreased plasma norepinephrine in normoxic and hypoxic pups. Hypoxia alone increased the concentration of cholesterol esters in the adrenal gland; this increase was due to increases in cholesterol ester-associated oleic (18:1n9), docosahexaenoic (22:6n3), arachidonic (20:4n6), and adrenic (22:4n6) acids. Hypoxia also increased diglyceride-associated adrenic acid. Guanethidine treatment attenuated the hypoxia-induced increase in cholesterol ester-bound arachidonic and adrenic acids. Guanethidine also decreased saturated fatty acid concentrations and increased n3 fatty acid-enriched triglycerides. The results support the idea that the ACTH-independent corticosterone response to hypoxia in the neonatal rat is mediated by specific, sympathetically driven alterations in the adrenal lipid profile.     

Catecholamines in adrenergic nerve fibers of the lymph nodes after sympathectomy

Using Falck method in combination with microfluorimetry, catecholamine level in adrenergic nervous fibers has been measured in the canine popliteal lymph nodes, normal and in 12 h, 7, 30, and 90 days after unilateral lumbar sympathectomy. During first 24 h after the operation the level of catecholamines is for certain increased in the nervous fibers of the lymph node of the sympathectomized extremity. In 30 days after the sympathectomy their content drops at the side of the operation and increases in the contralateral extremity. By 3 months the equilibrium of the catecholamine content is restored in the nervous fibers of the lymph nodes in the homo- and contralateral extremities at the level higher than in the control. A conclusion is made that under conditions of unilateral sympathectomy only a partial sympathectomy of the popliteal lymph node is reached. All luminiscent adrenergic nervous fibers of the sympathectomized lymph node are processes of neurons, situating in the contralateral sympathetic trunk, or neurites of cells in sacral nodes, getting their preganglionic fibers from the contralateral trunk. The changes in catecholamine concentrations mentioned are considered as a compensatory reaction, directed to maintenance of general homeostatic equilibrium under conditions, when the nervous system transfers to a new level, ensuring the partly desympathized tissue by mediators.