Adrenal Enucleation Research Articles

Immunoreactive ACTH and gamma-MSH in rat plasma during early stages of adrenal regeneration.

Recent evidence suggests that in addition to ACTH the pro-gamma-melanotropins play a role in controlling both the steroidogenic activity and growth of the adrenal cortex. By using the regenerating gland as a model for rapid adrenal growth, studies were carried out to monitor plasma ACTH and pro-gamma-melanotropins during the acute phase following adrenal enucleation. Adrenal enucleated rats (experimental group) were uninephroadrenalectomized; controls were uninephrectomized or uninephroadrenalectomized. At intervals up to 96 h after surgery, animals from each of the three groups were killed under quiescent conditions at the low and high points of their circadian rhythm. The plasma concentrations of both ACTH and 11 K gamma-melanocyte-stimulating hormone (MSH) in the adrenal enucleated rats were markedly elevated as compared with either control group at each time point monitored. However, there were no significant differences in plasma ACTH or 11 K gamma-MSH between the two control groups, and the levels of plasma 6 K gamma-MSH remained unchanged in all three groups throughout the experiment. These data are consistent with a role for pro-gamma-melanotropins in adrenal regeneration.

The antihypertensive effect of dietary potassium chloride loading in rats with adrenal regeneration hypertension.

Adrenal regeneration hypertension was induced in male Wistar rats by unilateral adrenal enucleation, contralateral adrenalectomy and the provision of a 1% (w/v) NaCl solution for drinking. A fivefold increase in dietary KCl content caused a significant reduction in the systolic blood pressure of hypertensive rats but not of control rats. During the increase in potassium intake there was a marked polydipsia. When 1% NaCl solution was the drinking fluid, the resultant increase in sodium intake was associated with an abolition of the antihypertensive effect of potassium loading, but when the sodium intake was held constant, the antihypertensive effect was maintained. In rats with adrenal regeneration hypertension, plasma volume was significantly higher, and packed cell volume and plasma protein concentrations were significantly lower than in control rats. These differences were abolished after 4 days of dietary KCl supplementation. Increased dietary potassium intake was associated with significantly lower serum aldosterone concentrations and significantly higher plasma potassium concentrations in adrenal enucleated rats compared with controls. The possibility that a reduction in extracellular fluid volume (due to a natriuresis) and/or a peripheral vasodilatation contributed to the antihypertensive effect of KCl loading is discussed.

Inhibition of the pathogenesis of spontaneous hypertension in SHR by gonadectomy

Male spontaneously hypertensive rat (SHR) originated from Kyoto-Wistar (WKY) were divided into 4 groups ; intact, castration (cast) performed at 4 weeks old (W) and adrenal enucleation (enucl) at 10W, cast at 4W and enucl at 22W, and enucl at 10W and cast at 22W. This would indicate 1) enucl-adrenal in the presence or absence of gonad increases significantly blood, pressure (BP) in both SHR and WKY, 2) gonadectomy significantly retards BP in both enuci-adrenal bearing and intact SHR, 3) gonadectomy did not alter the BP in WKY. These indicates that gonadal hormone(s) play of important role in the etiology of essential hypertension.

Development of hypertension and cataract in spontaneously hypertensive rats

The investigations were performed on 3 groups of untreated, spontaneously hypertensive Wistar rats of the Okamoto line. All the rats in Group I developed arterial hypertension within 16 weeks of birth and 33 percent of them developed cataracts within 22 weeks. Reserpine application suppressed hypertension and cataract development in all the animals in Group II. After unilateral adrenalectomy and contralateral adrenal enucleation (Group III), hypertension and cataracts developed in both treated and untreated animals; in the former, however, blood pressure was about 10 percent higher and cataracts developed about 6 weeks earlier than in the untreated rats. These findings support the hypothesis that arterial hypertension may be involved in cataract development.

Endocrine Pharmacology of SHR (Report 5) : Retardation in the development of spontaneous hypertension by gonadectomy before or after adrenal enucleation

Spontaneously hypertensive male rats (SHR) of Kyoto-Wistar (KW) strain were divided into 3 groups : castration (cast) performed at 4 weeks old (W) and adrenal enucleation (enucl) at 10 W as group 1, cast at 4 W and enucl at 22 W as group 2, and enucl at 10 W and cast at 22 W as group 3. Systolic blood pressure (BP) was measured by an indirect tail cuff method. Group 1:4 W cast rats showed a significantly lower BP as compared with intact SHR up to 22 W ; 10 W enucl rats showed a significantly higher BP over intact SHR up to 22 W ; and cast plus enucl rats showed a significantly higher BP over cast only-rats, but they showed a significantly lower BP compared to enucl only-rats. Group 2 : Rats bearing cast at 4 W and enucl at 22 W manifested progressively significantly BP, and values reached a level comparable to that of cast plus enucl rats as shown in group 1. The BP of these two groups were significantly below those of intact SHR until 35 W. Group 3 : Rats that received enucl at 10 W showed significant elevation in BP over the intact SHR up to 22 W ; but BP did not rise following cast at 22 W, and the BP was significantly below that of enucl only-rats. These values reached a level comparable to that of intact SHR. These results suggest that 1) enucl in the presence or absence of gonad increases significantly BP in both SHR and KW, 2) gonadectomy decreases significantly BP in enucl SHR and retards significantly BP in intact SHR ; however, 3) gonadectomy did not alter the BP in KW rats. It is concluded that gonad or gonadal hormones play an important role in the genesis of essential hypertension.

Effect of adrenal enucleation on inner medullary collecting duct function in the rat

Page F453: H. H. Bengele and E. A. Alexander. “Effect of adrenal enucleation on inner medullary collecting duct function in the rat.” Page F456: The following acknowledgment should be added: The accomplishment of this work was helped by the National Biotechnology Resource in Electron Probe Microanalysis, Claude Lechene Director, Harvard Medical School. This work was supported by Grant 5-P41-RR00679 from the National Institutes of Health.

Mineralocorticoid activity of 19-nor-DOC and 19-OH-DOC in adrenalectomized rat.

Excess mineralocorticoid activity is thought to be responsible for the increased sodium reabsorption found after adrenal enucleation, but no known mineralocorticoid has been demonstrated in quantities sufficient to account for this antinatriuresis. 19-Hydroxydeoxycorticosterone (19-OH-DOC) has been synthesized by the incubated enucleate adrenal capsule and 19-nordeoxycorticosterone (19-nor-DOC), a possible metabolite, has been found in the urine of rats with regenerating adrenal glands. To evaluate the in vivo mineralocorticoid potency of these steroids, we studied glucocorticoid-replete adrenalectomized rats and measured the sodium and potassium excretion after administration of these steroids. Our results indicate that 19-nor-DOC has equipotent antinatriuretic activity compared to aldosterone but was less kaluretic. 19-OH-DOC had no significant antinatriuretic or kaluretic activity. We conclude that 19-nor-DOC is a potent mineralocorticoid and may be responsible for the enhanced sodium reabsorption found after adrenal enucleation.

Enhanced protein synthesis of heart in adrenal-regeneration hypertension and its reduction following antihypertensive treatment.

After unilateral nephrectomy and bilateral adrenal enucleation at 5 weeks of age, salt-loaded rats developed hypertension (ARH) at 6 weeks. Fibrous vascular protein and in vivo incorporation of 3H-lysine into this protein fraction were measured at 15 weeks of age in these animals. This study demonstrates: (1) that incorporation rates of 3H-lysine into cardiac collagen and elastin in ARH rats were greater than in control rats (p less than 0.001, respectively), and (2) that administration of phenoxy-benzamine hydrochloride decreased the incorporation of tritiated lysine into cardiac collagen in ARH rats, concomitant with a reduction in blood pressure. Based on these findings, increased synthesis of cardiac collagen and elastin appears to play an important role in the development of hypertension in ARH.

Mineralocorticoid activity of 19-nor-DOC and 19-OH-DOC in toad bladder.

Adrenal enucleation is followed by a period of increased sodium reabsorption thought to be due to excess mineralocorticoid activity. However, it has not been demonstrated that increased production of any known mineralocorticoid accounts for this antinatriuresis. Recently, 19-hydroxydeoxycorticosterone (19-OH-DOC) was found in incubates of regenerating adrenal capsules 3-4 days postenucleation and 19-nordeoxycorticosterone (19-nor-DOC) was identified in the urine of rats with regenerating adrenals. Because it was possible that these hormones might play a role in the sodium retention after adrenal enucleation, we compared the mineralocorticoid activity of these steroids to aldosterone using the toad bladder. Using short-circuit current as a measure of sodium transport, we found that 19-OH-DOC (10(-8) M) had no significant effect on sodium transport. However, 19-nor-DOC (10(-8) M) increased sodium transport to a degree not different from aldosterone (10(-8) M). Furthermore, the onset of action, duration of activity, and inhibition of effect of 19-nor-DOC by spironolactone were not different from that of aldosterone. We conclude that 19-nor-DOC exhibits a significant effect on sodium transport and thus has the potential to play a role in the sodium retention following adrenal enucleation. Under the conditions of these studies, 19-OH-DOC exhibited no effect on sodium transport.

Return of pituitary-adrenal function after adrenal enucleation or transplantation: diurnal rhythms and responses to ether.

Adrenocortical diurnal rhythms and responses to ether vapor were studied in rats 1, 3, and 5 weeks after bilateral adrenal enucleation, autotransplantation, or sham transplantation in order to 1) determine whether diurnal rhythms in the plasma corticosterone concentration and adrenal responsiveness to ACTH are dependent on innervation of the adrenals, 2) compare regeneration of function of transplanted and enucleated adrenals, and 3) investigate adrenal mass-related nonsteroidal inhibition of ether-stimulated ACTH secretion. Rats in both enucleate and transplant groups exhibited significant morning-evening differences in adrenal and plasma corticosterone concentrations and significant adrenocortical responses to ether 3 and 5 weeks, but not 1 week, after surgery. The morning-evening differences in corticosterone concentration occurred in the absence of significant morning-evening variation in the plasma ACTH concentration, supporting our previous finding of a diurnal rhythm in adrenal responsiveness to ACTH. The responsiveness rhythm cannot be dependent on adrenal nerves unless transplanted adrenals receive functionally specific reinnervation within 3 weeks. The processes of regeneration of function after enucleation and after transplantation are similar; there were no differences in plasma or adrenal corticosterone values between rats in enucleate and transplant groups at any time or under any condition tested. As regeneration progressed, plasma ACTH responses to ether declined in both enucleate and transplant groups in the absence of changes in plasma corticosterone feedback. These results support our previous finding of adrenal mass-related nonsteroidal suppression of ACTH responses to ether.

Sodium excretion after adrenal enucleation and during adrenal regeneration hypertension.

AbstractRenal function following saline infusion (10% body wt) has been studied in four groups of rats 3 to 5 days after operation: Sham (S), Adrenal Enucleation (AE), Unine-phrectomy (N), and AE + N. The purpose of the study was to clarify the mechanisms of the effect of N on sodium excretion in AE. AE excreted significantly less sodium, 6.7 ± 1.3 μEq/min, than S, 29.7 ± 2.7 μEq/min. Sodium excretion by N, 25.4 ± 5.3 μEq/min and AEN, 19.4 ± 3.2 μEq/min were not different from each other or S, but greater than AE (P < 0.01). When AE (two kidneys) was compared with AEN (one kidney), the filtered sodium was not significantly different. Thus, it is concluded that the greater natriuresis in AEN versus AE is most likely secondary to a difference in tubular sodium reabsorption. Renal function following saline infusion (10% body wt) has been studied after the development of adrenal regeneration hypertension (6 weeks postsurgery) in AEN rats and their control groups N. Mean blood pressure was significantly elevat...

Sodium balance after adrenal enucleation

To better define the relationship between adrenal enucleation (AE), sodium retention and adrenal regeneration hypertension (ARH), we measured daily sodium balance in rats after bilateral adrenal enucleation with (AEN) and without uninephrectomy (AE), and before and after development of ARH, along with the appropriate control groups. We found that both AE and AEN groups retained sodium during 7 days after surgery; AE 1.16 +/- 0.24 and AEN 1.32 +/- 0.33 meq/100 g body wt. Sham-operated, uninephrectomized rats and AE rats treated with spironolactone were in zero sodium balance. In the AEN rats after the development of ARH (BP greater than 150 Torr), zero sodium balance was also noted. Only AEN rats developed hypertension while sham-operated, uninephrectomized rats and AE rats with both kidneys remained normotensive for 28 wk. In summary, we have demonstrated that for 1 wk after AE, rats are in positive sodium balance and this is reversed by spironolactone but not by uninephrectomy.

Peripheral 6-hydroxydopamine administration in the rabbit (Oryctolagus cuniculus): effects on Pavlovian conditioning.

The present experiment studied the effects of 6-hydroxydopamine (6-OHDA) administration and adrenal enucleation on differential classical conditioning of somatic and cardiovascular changes in the rabbit. Heart rate and blood pressure conditioned responses (CRs) were relatively large decreases in rate and slight depressor responses, respectively, which were both attenuated by 6-OHDA administration and adrenal demedullation. Frequency of eye-blink response to the reinforced conditioned stimulus was diminished by sympathetic interference during the middle sessions of conditioning, thus producing a decrement in eye-blink discrimination. Electromyographic CRs, on the other hand, were not affected by peripheral catecholamine reduction. These results are discussed in terms of the role of afferent autonomic feedback in influencing the acquisition of somatomotor behaviors.

Adrenal regeneration. Time course, effect of hypothalamic hemi-islands and response to unilateral adrenalectomy.

Regeneration of rat adrenals was studied after bilateral enucleation to determine whether there is a neural component mediating this process as there is in compensatory adrenal growth after unilateral adrenalectomy. Regeneration was approximately 50% complete (based on criteria of wet weight and DNA content) by 10 days after enucleation; at this time circulating ACTH levels were twice as high in enucleates as in sham-operated controls, but corticosterone levels were normal. Regeneration was apparently complete at sometime between 3 and 6 weeks and circulating ACTH and corticosterone levels were normal at these times compared to controls. Unilateral adrenal enucleation resulted in compensatory growth of the opposite gland, not regeneration of the enucleated gland. Unilateral hypothalamic hemi-islands made with a Halász knife resulted in bilateral augmentation of adrenal regeneration at 10 days and 6 weeks. From these results we conclude that adrenal regeneration after bilateral enucleation occurs by different afferent and efferent mechanisms than compensatory adrenal growth after unilateral adrenalectomy. Additional studies were performed in rats 3 and 6 weeks after adrenal enucleation to test whether the adrenal medulla participates either in compensatory adrenal growth or in the augmented ACTH response to ether vapors observed in unilaterally adrenalectomized rats. Normal compensatory adrenal growth occurred 3 days after unilateral adrenalectomy in rats bilaterally enucleated 6 weeks earlier. Prior enucleation did not inhibit the increased ACTH response of unilaterally adrenalectomized rats to ether. Therefore, the adrenal medulla does not mediate compensatory adrenal growth or the augmented ACTH response of unilaterally adrenalectomized rats to ACTH-releasing stimuli.

Adrenal demedullation and peripheral 6-OHDA administration in the rabbit: Effects on body weight, general activity and cardiovascular responsivity

Two experiments were undertaken to determine the effects of systemic 6-hydroxydopamine (6-OHDA) administration and adrenal enucleation on body weight, brain and heart norepinephrine, general activity, and cardiovascular responsivity in the rabbit. 6-Hydroxydopamine produced long lasting, dose related decreases in baseline blood pressure (BP) and in pressor responses following electric shock. Partial reversal of the BP changes was observed in nonenucleated animals tested 20 days after 6-OHDA administration but not in enucleated animals tested 5, 10 or 20 days post-injection or in control animals tested 5, 10 or 15 days after vehicle injection. Although 6-OHDA administration produced transient weight loss and activity decrements, no long term weight or activity changes were observed.

Blood pressure in conscious and anesthetized adrenal-enucleated Sprague-Dawley and Wistar-Furth rats.

Systolic blood pressure was measured weekly in conscious and in anesthetized female Sprague-Dawley (SD) and Wistar-Furth (W/Fu) rats following adrenal enucleation, unilateral nephrectomy, and the imposition of a high salt intake. SD rats quickly developed adrenal-regeneration hypertension (ARH) which progressed rapidly, and was identifiable in both the conscious and the anesthetized state. W/Fu rats slowly developed mild ARH, which, with a single exception, was identifiable only in conscious animals; the arterial pressures were within the normotensive range under anesthesia. The depressor effect of ether was also greater in adrenal-enucleated W/Fu than in similarly prepared SD rats, and in hypertensives than in normotensives. It is concluded that blood pressure measurements taken under anesthesia may not be representative of the true resting blood pressures: this is likely to be a particularly crucial problem in identifying early hypertension under circumstances and in rat strains highly susceptible to the depressor effects of ether.

Natriuresis after adrenal enucleation: effect of spironolactone and dexamethasone.

After adrenal enucleation, rats have an impaired ability to excrete a salt load because of enhanced collecting duct reabsorption. This antinatriuretic effect, thought to be secondary to a mineralocorticoid-like substance secreted by the enucleate gland, can be reversed by treatment with spironolactone or dexamethasone. To define the renal mechanisms involved in this drug-induced natriuresis we have utilized clearance and micropuncture techniques in enucleate saline-expanded rats that were treated with either spironolactone (S) or dexamethasone (D), or were untreated (U). Sodium excretion was clearly increased after S, 13.9, and D, 19.3 mueq/min vs. u, 5.9 mueq/min. The mechanisms of this natriuresis, however, were dissimilar. Spironolactone-treated rats were not different from untreated rats except with regard to function beyond the superficial late distal tubule, where U rats reabsorbed over 50% of the delivered sodium. In the S group 38% of the excreted sodium was added along this tubular locus, 5.2% of the filtered sodium reaching the late distal tubule and 7.3% appearing in the urine. These data demonstrate that the natriuresis after S is secondary to the net addition of sodium beyond the superficial late distal tubule. Spironolactone may work by inhibiting a mineralocorticoid-like product of the enucleate gland and, thereby, eliminate the sodium-retaining effect of this product. The natriuresis after D, however, can be explained solely on the basis of a markedly increased filtered load of sodium traversing the nephron.

Effects of prostaglandin E2 and prostaglandin inhibitors on adrenal regeneration hypertension.

The effects of prostaglandin E2 (PGE2) and a prostaglandin inhibitor, indomethacin, on the development of adrenal regeneration hypertension (ARH) were investigated. Weanling female rats underwent right adrenonephrectomy and left adrenal enucleation. PGE2 was injected subcutaneously daily in dosages of 0, 20, 40 and 80 mug/day. Indomethacin, 1 mg/kg, was administered twice daily by gavage. Blood pressures were determined by a tail and cuff plethysmographic method at 3, 5, and 7 wk after surgery. Increases in dosage of PGE2 produced a progressive reduction in mean blood pressures, heart, and kidney weights. Indomethacin produced significant increases in mean blood pressure, heart, kidney, and adrenal weights. The effects of aspirin and indomethacin on the blood pressures of rats with right adrenalectomy, left adrenal enucleation, and intact kidneys were studied. Administration of asprin twice daily (25 or 50 mg/kg) produced a fall in blood pressure, body and heart weight. Administration of 1 mg/kg twice daily of indomethacin resulted in a significant increase in blood pressure at 3 wk, and 0.1 or 1 mg/kg caused significant increases at 5 wk. The heart, kidney, and adrenal weights also showed increases with indomethacin administration. This study suggests that a deficiency of renal PGE2 may be involved in the etiology of ARH.

Effect of adrenal enucleation on sodium excretion in the rat

After the adrenal glands are removed without their capsules, so-called adrenal enucleation, rats initially retain sodium, and, after adrenal regeneration, escape from salt retention. To define the renal mechanisms involved in this alteration in salt handling, we have utilized clearance and micropuncture techniques in three groups of saline-expanded rats that were sham-operated (S), enucleated (AE), or escaped after adrenal regeneration (E.) Sodium excretion was clearly blunted after AE, 5.5 mueq/min vs. 20.5 for S and 18.7 for E. Although glomerular filtration rate (GFR) and filtered load of sodium were lower in AE rats, the delivered load of sodium beyond the late distal tubule was not different among the groups: 0.30 neq/min for AE, 0.42 for S, and 0.40 for E. This was a consequence of strikingly greater sodium reabsorption in the loop of Henle and distal tubule in both the S and E rats. In the collecting duct over 50% of the delivered sodium was reabsorbed by the AE rats while over 30% of the excreted sodium was added in this tubular segment in the other groups. These data demonstrate that the impaired natriuresis after adrenal enucleation appears to be due to striking differences in collecting duct function. Since adrenal regeneration in the escape animals reverses this sodium retention, the effect is probably related to some alteration in adrenal hormone production. Sodium excretion in markedly expanded normal rats also appears to be determined by the net addition of sodium in the collecting duct.

Adrenal Mitochondrial and Serum Corticosteroid Studies in RatsResistant to Adrenal-Regeneration Hypertension (ARH)

Female rats of the Wistar-Furth (W/Fu) strain appear to be resistant to the development of adrenal regeneration hypertension. At a time period, after adrenal enucleation, when Holtzman female rats had elevated serum 11-deoxycorticosterone levels and were hypertensive, none of the W/Fu rats became hypertensive. In vitro adrenal studies after quiescent kills of W/Fu rats indicated that cholesterol side chain cleavage activity was greater in mitochondria from regenerating adrenals than from controls. Both serum deoxycorticosterone and corticosterone levels were significantly greater in the adrenal-enucleated group. These studies were repeated in animals which were given a standard ether anesthetic stress. Ether stress increased cholesterol side chain cleavage activity comparably in control and adrenal-enucleated rats and also increased their serum deoxycorticosterone and corticosterone levels. Adrenal-enucleated Wistar-Furth rats had higher serum deoxycorticosterone levels than controls, whereas controls had higher serum corticosterone levels than the adrenal-enucleated group after the ether stress. These results indicate that although the adrenal-enucleated W/Fu rats have increased serum deoxycorticosterone levels, none of these rats develop frank hypertension. This suggests a resistance to deoxycorticosterone-induced hypertension in this strain of rat.