Adrenalectomized Rabbits Research Articles

Eosinopenia of acute infection: Production of eosinopenia by chemotactic factors of acute inflammation.

One distinctive aspect of the response to acute inflammation involves a rapid and persistent decrease in the numbers of circulating eosinophils, yet the mechanisms of this eosinopenia are undefined. One possibility is that the abrupt eosinopenia may be the result of release of small amounts of the chemotactic factors of acute inflammation into the circulation. These studies were designed to examine the numbers of circulating eosinophils after an intravenous injection of zymosan-activated serum, partially purified C5a or the synthetic peptide, N-formyl-methionyl-leucyl-phenylalanine. Each of these factors caused a virtual disappearance of circulating eosinophils within 1 min, a transient return of eosinophils to approximately 50% of control levels after 10-90 min, and a subsequent decrease which persisted for 5 h. In contrast, the numbers of circulating heterophils, although dropping transiently, rapidly returned and rose to elevated levels for 6 h after injection. The response was not caused by adrenal mediation as it occurred normally in adrenalectomized rabbits. Two chemotaxins of allergic inflammation, histamine and the tetrapeptide valine-glycine-serine-glutamic acid, did not cause significant eosinopenia. Circulating granulocytes of patients undergoing hemodialysis, which has been reported to activate complement, demonstrated similar eosinopenic and neutropenic-neutrophilic responses. Thus, in rabbits and in man, intravascular activation or injection of chemotactic factors (C5a or N-formyl-methionyl-leucyl-phenylalanine) causes a brief, nonspecific granulocytopenia followed by a prolonged eosinopenic-neutrophilic response analogous to that seen during acute infection.

Effects of aldosterone and potassium-sparing diuretics on electrical potential differences across the distal nephron.

We have previously shown that the transtubular potential of the rabbit cortical collecting tubule varies in concert with changes in plasma mineralocorticoid levels, while the potential of the distal convoluted tubule is invariant with such changes. In the present studies we have examined the effects of in vitro addition of d-aldosterone to isolated tubules, as well as the effects of triamterene and spirolactone. d-Aldosterone (0.2 mum added to the perfusate or 1 muM added to the bathing medium) resulted in a marked stimulation of the transtubular potential difference (lumen-negative) after a short latent period. d-Aldosterone had no effect on the potential difference of distal convoluted tubules of intact or adrenalectomized rabbits. Both the magnitude of the response and the length of the latent period in the cortical collecting tubule after aldosterone were markedly temperature-dependent. Triamterene caused a gradual but reversible inhibition of the potential difference in the cortical collecting tubule but had no effect in the distal tubule. Spirolactone, when added before aldosterone, blocked the electrical response to the hormone in the cortical collecting tubule, and produced a gradual inhibition of the potential difference in mineralocorticoid-stimulated tubules. Spirolactone had no effect on the potential difference of the distal tubule. We conclude that (a) the influence of aldosterone on the potential across the distal nephron is restricted to the distal convoluted tubule, (b) the electrical response to aldosterone and the latent period are temperature-dependent, (c) the response to aldosterone is blocked by spirolactone, and (d) triamterene inhibits the potential difference only in the cortical collecting tubule.

Effets de la surrenalectomie et de l'administration d'hydrocortisone sur l'activite de l'adenylate cyclase de cellules adipeuses du lapin

Adenylate cyclase activity in rabbit adipocyte plasma membranes was studied with special reference to the effects of adrenalectomy and administration of cortisol in vivo. Adrenalectomy was accompanied by an increase in adenylate cyclase activity during basal conditions; cortisol (5 mg/kg body wt., intramuscularly) partly prevents this effect of adrenalectomy. The response of adenylate cyclase to corticotropin, epinephrine and norepinephrine stimulation was higher in the adrenalectomized rabbit than in the sham operated animal. Our in vitro results were in agreement with the striking fat mobilization observed in rabbit plasma after adrenalectomy and with the hypolipemic effects of cortisol we had previously observed in both normal and adrenalectomized rabbit.

Effect of aminoglutethimide and adreno-blocking agents on morphine-induced hyperglycemia

Morphine-induced hyperglycemia is completely suppressed in adrenalectomized rabbits. Phentolamine does not modify the effects of morphine. Aminoglutethimide and propranolol substantially reduce morphine-induced hyperglycemia which is partially mediated by β-adrenergic receptors.

Participation of adrenal hormones in the genesis of arterial hypertension of hypothalamic origin

Continuous many-hour stimulation of the hypothalamic negative emotiogenic centres (ventromedial nuclei) evoked a stable arterial hypertension with a peculiar phasic dynamics of the adrenal secretory activity in waking immobilized rabbits. Bilateral extirpation of the adrenal glands decreased the initial level of the average arterial pressure, inhibiting development of stable arterial hypertension. Many-hour stimulation of the mentioned structures also produced stable arterial hypertension in adrenalectomized rabbits if preceded by the administration of hydrocortisone together with adrenaline. Against the background of separate administration of hydrocortisone and adrenaline to adrenalectomized rabbits, many-hour stimulation of the ventromedial hypothalamus evoked a short-term rise in the arterial pressure. A conclusion was drawn that activation of hormones of the adrenal cortical and medullary layers played an important part in the formation of stable arterial hypertension in rabbits under continuous many-hour stimulation of the hypothalamic negative emotiogenic centres.

On the mechanism of activation of the hypothalamo-pituitary-adrenal reaction to changes in the environment (the ‘alarm reaction’)

The amount of circulating noradrenaline increases considerably in parallel with an improvement in cardiovascular haemodynamics in adrenalectomized rabbits after intravenously injected hydrocortisone. In view of this finding, that as well as a constant regulation with negative retroaction of the corticotrophic-releasing factor-adrenocorticotrophic hormone (ACTH)—cortisol system, there exists an externally controlled servomechanism from nervous system activity related to the environment. Hydrocortisone favours passive avoidance, extinction and facilitates the activity of the chohnergic inhibiting system; ACTH facilitates active avoidance and catecholaminergic activation. It has already been demonstrated that stimulation of the inhibiting system or inhibition of the activating system released noradrenaline from the peripheral nerves of an adrenal ectomized animal. It therefore seems that the early release of ACTH after aggression is capable of favouring locomotor activity in ‘flight or fight’. If the latter is effective, there is a return to the previous behavioural and endocrine balance. On the other hand, if ‘flight or fight’ should be ineffective, there arises a vicious circle with positive retroaction, because secondary secretion of glucocorticoids will maintain inhibition and considerable activity in the noradrenergic system. The significance of the alarm reaction and the secondary release of the mineralocorticoids are discussed as well as the central mechanism of allegedly psychosomatic, illness. Aggression, as well as the lesion it induces, causes a reaction from the organism subjected to aggression. This is a non-specific reaction to which Selye (1936) has drawn attention. This reaction sets the central nervous system in action, which activates the vegetative nervous system and the endocrine system through the hypothalamus and the pituitary gland. In the vegetative system and the vasomotor changes related to it, the alarm syndrome has to be understood as a way to induce flight or fight, which allows the organism to move away from the aggressor. When this behaviour is impossible or ineffective the vasomotor reaction is threatened and it is depressed or inhibited (Laborit, 1952). Resuscitation techniques involving central or peripheral inhibitors, such as lytic cocktails, neuroplegy or neuroleptanalgesia, derive from this concept. The neuro-endocrine significance of the alarm reaction is still not understood and resuscitation techniques are quite empirical in relation to it.

Effect of ACTH, α-MSH, and β-Lipotropin on Calcium and Phosphorus Metabolism in the Rabbit

Studies were undertaken to investigate the effects of synthetic 1-24 adrenocorticotropin (ACTH), bovine alpha melanocyte-stimulating hormone (alpha-MSH), and ovine beta lipotropin (beta-LPH) on plasma calcium and phosphate in rabbits. Equimolar concentrations of these hormones were infused intravenously in intact and thyroidectomized animals. In addition, ACTH was similarly administered to adrenalectomized rabbits. ACTH, alpha-MSH, and beta-LPH all lowered plasma calcium and raised plasma phosphate. These changes were not prevented by prior thyroidectomy. ACTH was equally effective in inducing hypocalcemia and hyperphosphatemia in the absence of the adrenal glands, while adrenalectomy alone raised plasma calcium. From these findings we have concluded that 1) ACTH, alpha-MSH, and betaLPH affect phosphate as well as calcium metabolism; 2) these hormones do not act by releasing calcitonin; and 3) ACTH exerts its hypocalcemic-hyperphosphatemic effect, at least in part, independently of its trophic action on the adrenal glands.

The Role of ACTH and Adrenal Glucocorticoids in the Salt Appetite of Wild Rabbits [Oryctolagus cuniculus (L)

The selective appetites of wild rabbits for 500 mEq/1 solutions of NaC1, KC1, MgC1(2), and CaC1(2) were studied in intact and adrenalectomized rabbits during daily treatment with either 4 IU long acting ACTH, 1.0 or 2.5 mg cortisol acetate, or 2.5 mg corticosterone. The animals were individually caged and external sodium balances performed. In intact rabbits, cortisol or corticosterone produced a significant stimulation of NaC1 appetite. The response to concurrent dosage of cortisol and corticosterone was less than half of that obtained with ACTH which produced a comparable alteration of blood glucocorticoid levels but a 10-fold increase in NaC1 intake. CaC1(2) intake was increased in intact rabbits by cortisol treatment but not by corticosterone or ACTH. Adrenalectomized rabbits maintained on daily steroid replacement therapy of 0.1 mg deoxycorticosterone acetate and 0.75 mg cortisone acetate showed a normal pattern of electolyte, food, and water intake. Under these conditions ACTH produced a 4-fold increase in NaC1 intake. Further addition of cortisol and corticosterone to steroid replacement therapy produced an increase in NaC1 intake comparable to their effect on normal rabbits. Thereupon supplementation with ACTH resulted in an increase to a level at least as great as that found in ACTH treated, normal rabbits. The effects of ACTH and glucocorticoids on NaC1 appetite were synergistic. Sodium balance showed that increases in NaC1 intake were not the result of the treatment initially producing a body sodium deficit, which was then corrected by increased intake. The results provide further evidence for the hypothesis that NaC1 appetite may be hormonally regulated, and demonstrate that ACTH is capable of stimulating NaC1 intake by a previously unsuspected non-adrenal pathway.

State of the energy metabolism in muscles of adrenalectomized rabbits during contraction

State of the energy metabolism in muscles of adrenalectomized rabbits during contraction

Induction of lactation in the guinea-pig.

The initiation of lactation is a complex phenomenon involving the interaction of a number of hormones (see Cowie, 1966; Meites, 1967). Several experiments with hypophysectomized, ovariectomized and/or adrenalectomized mice (Nandi, 1959), rats (Lyons, Li & Johnson, 1958) and guinea-pigs (Nelson & Gaunt, 1937) indicate that the primary hormones involved in the initiation of lactation are prolactin and cortisol or corticosterone. Adrenal steroids stimulate secretory activity in the mammary glands of pregnant rats (Talwalker, Nicoll & Meites, 1961). In the mouse, Nandi & Bern (1961) suggested that inadequate secretion of glucocorticoids was the limiting factor in initiating mammary secretion during pregnancy. Cortisol acetate alone in pregnant rabbits (Talwaker et al. 1961) and prolactin alone in adrenalectomized rabbits (Cowie & Watson, 1966), can stimulate secretory activity. We have tried to find the hormonal requirements for lactogenesis in the guinea-pig. Thirty-five adult male guinea-pigs were castrated under ether anaesthesia. Beginning 2 days after

Endotoxin fever and tolerance in totally adrenalectomized rabbits.

SummaryThe initial febrile response, the acquisition of pyrogenic tolerance, and the titer of anti-“0” antibody to a Boivin preparation of E. coli endotoxin was not significantly altered in totally adrenalectomized rabbits maintained healthy with DOCA.

Effects of hydrocortisone acetate and estradiol in normal and adrenalectomized salt deficient rabbits.

These experiments were undertaken to determine the involvement of the adrenocortical hormones in the inhibition by estrogens of the polyuric-polydipsic syndrome induced by salt deficiency in the male rabbit. Daily measurements were made of body weight, water intake and urinary volume, Na† and K† during 10 consecutive days of food deprivation in normal and adrenalectomized male rabbits receiving 17β-estradiol (100 µg/day) and/or hydrocortisone acetate (Fac, 2.5 mg/day) for the first 5 days. Normal males, when deprived of food, developed the typical polyuria and polydipsia which were accompanied by a marked rise in urinary Na†. The administration of Fac further enhanced significantly the fluid exchange during the first 5 days. The administration of estradiol completely inhibited the polyuriapolydipsia, and this effect per sisted into the second 5 days. Estradiol administration to the Fac treated rabbits not only abolished the enhancement due to Fac but depressed water intake and urine volume to values less ...

The effect of a natriuretic dose of angiotensin on rabbit kidney composition.

1. To obtain information about the mechanism of the natriuresis induced by angiotensin, its effect on the distribution of electrolytes, urea and water in rabbit kidneys was examined. 2. In five control experiments, after infusion of normal saline at a low rate for several hours, the animals were killed and their kidneys removed and analysed for Na, K, Cl, urea and water content at five levels from outer cortex to papilla. In five further animals, the infusion was changed to 1 μg kg−1 min−1 of angiotensin for 40 min. This induced a significant natriuresis. 3. Significant changes in tissue composition induced by angiotensin were reduction in the Na, Cl, and urea concentrations throughout the medulla and papilla, an increase in the water content in these regions and an increase in outer cortical Na and Cl concentrations. In the inner cortex the water content was increased and the urea content decreased. 4. Angiotensin produced similar changes in renal tissue in experiments in which the same protocol was used in eight adrenalectomized rabbits and in five rabbits with unilateral renal denervation. The changes seen were therefore ascribed directly to angiotensin and not to adrenal hormone release or sympathetic nerve stimulation. 5. The most likely interpretation of the results is that angiotensin inhibits Na reabsorption in the ascending limb of the loop of Henle. However, other explanations, including alterations in vasa recta blood flow, are possible.

The study on the activity of the hypothalamus and the limbic system under extreme cold.

From the viewpoint of the neurohumoral interaction in the control of body temperature, brain activity under extreme cold was studied by means of EEG observation and electrical stimulation, employing New Zealand white rabbits with chronically implanted bipolar electrodes in the several parts of the brain. During experiment, rabbits were free to move around on the observation table or in the cold box under constant illumination.The results were as follows:The EEG activity showed the following alterations during exposure to cold (at a temperature of 20°C below zero for a period of 12 hours).1. Exposure to the extreme cold brought about an enhancement of EEG activity in the medial preoptic area, ventromedial nucleus of the hypothalamus, posterior hypothalamus, periventricular stratum, hippocampus, medial amygdala, lateral septum and central grey, and suppression of EEG activity in the lateral preoptic area, lateral hypothalamus, lateral amygdala and medial septum. EEG recorded from the arcuate nucleus and its adjacent region did not show any notable change resulting from cold exposure. To summarize the above results, EEG of the areas belonging to the so-called sympathetic zone showed elevated activity under extreme cold. At the same time, some areas belonging to the so-called parasympathetic zone and the limbic system also showed an activated pattern during cold exposure. EEGs were recorded from the brain of immature rabbits of 14 to 40 days of age. It was suggested that the amygdala was the earliest center to develop for the regulation of body temperature. In the later stages of development the hippocampus takes the place of the amygdala in the thermo-regulatory mechanism.2. Repetitive cold exposure (20°C below zero for 12 hours per a day) and simultaneous EEG recording were carried out for a period of 7 or 10 days in summer. The change observed in the hippocampus, amygdala, medial preoptic area, periventricular stratum, ventromedial hypothalamus and posterior hypothalamus observed at the initial exposure gradually decreased, until the EEG activity in these areas was hardly influenced by the 5th or 10th exposure to cold. The activity of the limbic areas tended to lose reaction to cold exposure earlier than the latter.3. In order to elucidate the relation of increased activity in various parts of the brain to body temperature, a stimulation experiment was performed. Stimulation consisted of monophasic square wave pulses delivered unilaterally for one hour, 60 sec. on and 60 sec. off, at 0.5 msec. duration, 60 cps. The stimulation on each part of the brain caused a rise in rectal temperature. The change was divided into immediate effect (Effect during stimulation) and delayed effect (effect after stimulation). Immediate effect (rise of rectal temperature by 0.3 to 0.8°C) was observed by the stimulation of regions included in the so-called sympathetic zone of the hypothalamus such as the medial preoptic area, ventromedial hypothalamus and posterior hypothalamus and some areas of limbic system such as the amygdala, lateral septum and central grey. On the other hand, delayed effect was observed by the stimulation of the medial preoptic area, ventromedial hypothalamus (so-called sympathetic zone), lateral hypothalamus, arcuate nucleus (so-called para sympathetic zone), hippocampus, amygdala, lateral septum and central grey (limbic area). It may be supposed that the immediate effect was caused by neural factors or by fast-acting substances like epinephrine, and that the latter was brought about by slow-acting factors such as ad renocortical hormones or thyroid hormone.4. In order to clarify the significance of the delayed effect which might play an important role in the prolonged exposure to cold, electrical stimulation of the limbic area was carried out in adrenalectomized rabbits and thyroidectomized rabbits.

Mechanism of anti-shock effect of glucocorticoid in hemorrhagic shock in rabbit.

It was shown that the extreme susceptibility of adrenalectomized rabbits to hemorrhagic hypotension was mainly due to the absence of glucocorticoid.‘Take-up’ of shed blood in an elevated reservoir proceeded far earlier and more rapidly than in the non-adrenalectomized rabbit. This was accompanied by progressive diminution of pulse pressures, while the cardiac rate was reduced. At autopsy, no blood pooling was noticed except that due to acute right heart failure. Examination of right ventricular pressures revealed the presence of progressive secondary rise in systolic and diastolic pressures indicating an increase in the resistance of the pulmonary circuit. Pretreatment with physiological dose of Cortisone prevented these changes and inhibited the rapid progress of ‘take-up’. The significance of glucocorticoid therapy in hemorrhagic hypotension in rabbits which differed from that in dogs has been discussed.

Breakdown of Blood–Cerebrospinal Fluid Barrier for Calcium Ions in the Absence of Glucocorticoids

RABBITS become extremely susceptible to intravenous infusion of a solution of calcium chloride after adrenalectomy (our unpublished work). Unlike the intact animals, adrenalectomized rabbits easily succumb to shock, before cardiac disturbances caused by an enormous elevation of serum calcium content. Myosis and slight bradycardia appear at first, then cyanosis and a progressive decline in blood pressure follow. These symptoms were found to be quite similar to those induced by intracisternal injection of small amounts of calcium chloride solution in this animal species and could be prevented by pretreatment with glucocorticoids. We have therefore examined whether the increased susceptibility of adrenalectomized rabbits to the elevation of serum calcium content is caused by an increase in permeability of the blood–cerebrospinal fluid barrier or by an increased central susceptibility to a small increment in the concentration of calcium in the cerebrospinal fluid.

The hypothalamus and liver metabolism.

The results of our experiments on the influence of the hypothalamus upon liver metabolism in rabbits can be summarized as follow. The hypothalamus regulates the blood glucose and serum lipid content. By electrical stimulation of theb-sympathetic zone (the medial hypothalamic area), the liver glycogen decreases remarkably, while electrical stimulation of the c-parasympathetic zone (the lateral hypothalamic area) causes an insignificant change. The hypothalamus can also have a considerable effect upon the protein metabolism of the liver. The activities of tryptophan pyrrolase, tyrosine transaminase and alanine transaminase in rabbit liver are elevated by electrical stimulation of the sympathetic zone in normal rabbits and even in adrenalectomized rabbits. When the splanchnic nerve is stimulated electrically, the activities of glycogen phosphorylase, glucose-6-phosphatase and tryptophan pyrrolase of rabbit liver increase markedly. These results suggest that the hypothalamic influence upon liver enzymes is of neural nature.

Significance of glucocorticoids in preventing hypercalcemic shock in rabbits.

It has been observed that adrenalectomized rabbit are extremely susceptible to hypercalcemia. Intravenous infusion of CaCl2 solution induced easilya lethal hypotention accompanied by cyanosis before cardiac disturbancesdue to extreme hypercalcemia ensued. Autopsy showed a pronounced dilatation of pulmonary artery and right heart, suggesting pulmonary arteriolarspasm. Examination of the cerebrospinal fluid in the shocked state revealeda marked elevation of calcium concentration. In intact animals no suchelevation occurred and cardiac death followed in extreme hypercalcemia.Intracisternal injection of small amounts of CaCl2 solution in intact animalswas found to induce a quite similar type of shock observed in adrenalectomizedanimals in hypercalcemia. Thereby, bilateral cervical vagotomy could preventthe appearance of the shock, indicating that the shock was due to activationof pulmonary vagal vasoconstrictors.Pretreatment with glucocorticoid which completely reversed the increasedsusceptibility of adrenalectomized rabbits to intravenous infusion of CaCl2 solution was found also effective in preventing the entrance of calcium ioninto the cerebrospinal fluid. Thus it has been deduced that the hypercalcemicshock in the absence of glucocorticoid might be the result of the enhancedpermeability of the blood-cerebrospinal fluid barrier to calcium ion. Thesignificance of glucocorticoid for the maintenance of blood-cerebrospinal fluidbarrier and the central action of calcium ion in this animal species havebeen discussed.

DEVELOPMENT OF SHOCK-INDUCING FACTOR IN CANINE ENDOTOXIN SHOCK.

DURING the course of our investigations on the mechanism of enhanced susceptibility to endotoxin after adrenalectomy in dogs, it was found that a transferable shock-inducing factor develops in the absence of glucocorticoids. The shock induced by endotoxins which have no direct cardiovascular action has been difficult to interpret. There has been debate on the indirect mechanisms1, such as endotoxin-epinephrine synergism or histamine release. However, none could explain the effectiveness of glucocorticoids in preventing the endotoxin shock2. Concerning endotoxin susceptibility after adrenalectomy in rabbits, Fukuda3,4 has pointed out that the diminution of hepatic glycogen which follows the accumulation of endotoxin in liver might have an intimate relation to the development of circulatory weakness. Prevention of the attendant hypoglycaemia and the lactacidaemic acidosis by infusions of a hypertonic glucose and sodium bicarbonate solution has been shown to be effective in the recovery of adrenalectomized rabbits even after intravenous administration of the lethal dose of endotoxin (200 µg/kg; LD100).

Adrenal cortex and aqueous humour dynamics

The intraocular pressure was recorded manometrically or tonometrically in anaesthetized and unanaesthetized rabbits. Facility of aqueous humour outflow was measured by an in vivo perfusion technique and by tonography. The rate of aqueous humour flow was calculated from direct measurements of intraocular pressure, episcleral venous pressure, and facility of outflow. In rabbits, bilateral adrenalectomy lowered the intraocular pressure by decreasing the aqueous production to approximately one-half. The facility of outflow and the episcleral venous pressure were not appreciably affected. There was no significant correlation between the degree of reduction of flow or pressure and the concentrations of Na+, K+ and Cl− in venous plasma. Systemic administration of corticosteroids such as aldosterone, aldosterone 21-acetate, prednisolone 21-acetate, or a combination of deoxycorticosterone acetate and cortisone acetate did not influence the resistance to outflow, nor did it significantly restore the pressure and flow in adrenalectomized rabbits—neither when the drug was given shortly before the measurements were taken (2–7 hr) nor after prolonged treatment (7–9 days). The eye parameters of the rabbits treated with aldosterone 21-acetate were very similar to those observed in the rabbits treated with prednisolone 21-acetate and in the adrenalectomized animals, despite the greatly divergent values for Na+, K+ and Cl− in the venous plasma.