Methylandrostenediol hypertension induced without salt excess: observations on organ changes and serum composition

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Interaction between desoxycorticosterone treatment, fluid intake, sodium consumption, blood pressure, and organ changes in rats drinking water, saline, or surcose solution

Intact control and DOCA-treated rats were allowed to drink distilled water, a 1% NaCl solution, or a 5% sucrose solution. Fluid intake, blood pressure changes, and organoleptic responses were evaluated. Control rats drank more sucrose solution than saline and more saline than water. Hormone treatment slightly increased water intake and greatly augmented saline consumption, but invariably depressed that of sucrose solution even though a considerable polydipsia remained in effect. Hypertension and cardiorenal enlargement characterized all groups given DOCA. Both were substantially more severe in those also given excess salt, and only in that group were cardiovascular–renal lesions grossly visible.

Restoration of adrenal-regeneration hypertension in corticosterone-blocked rats by ACTH

Adrenal-regeneration hypertension developed uniformly in uninephroadrenalectomized, contralaterally adrenal-enucleated rats, but not in uninephroadrenalectomized controls, maintained on a high salt intake. Adrenal regeneration and the accompanying hypertension were both blocked by daily administration of 1 mg of corticosterone. One unit of ACTH gel given daily had no effect on either the blood pressure or the adrenal weight of rats with uncomplicated adrenal-regeneration hypertension or those in which blood pressure elevation was blocked with corticosterone. There were no significant differences in thymus weight between any of the foregoing groups. The daily administration of 4 units of ACTH permitted only slight enlargement of the adrenals of corticosterone-blocked, adrenal-enucleated rats, or of the hypertrophying adrenals of unilaterally adrenalectomized rats. Hypertension was fully restored to the former, but was not developed in the latter. Both groups displayed a degree of thymus involution. It would appear that full morphologic regeneration is not a prerequisite of adrenal-regeneration hypertension, but that adequate steroidogenesis to support the change can be elicited from an atrophied adrenal gland by adequate ACTH stimulation. The thymolytic effect of ACTH is analyzed for its possible relevance in respect to the secretory profile of adrenosteroids.

Hormonally maintained high blood pressure following adrenalectomy in rats with adrenal-regeneration hypertension and its possible significance in the etiology of that disorder

Rats were caused to develop adrenal-regeneration hypertension, and attempts were made to reproduce in them after adrenalectomy the same rate of blood pressure rise as occurred in animals allowed to retain enucleated adrenals, by using aldosterone, corticosterone, or a mixture of the two. Corticosterone at 2.5 mg/day caused a somewhat greater rate of blood pressure increase than occurred in rats retaining regenerating glands, but whereas the latter did not manifest thymus involution, hormone-treated animals did. At 1 mg/day there was a drop in blood pressure following adrenalectomy in rats with adrenal-regeneration hypertension, although not always to normotensive levels, and the characteristic hypotension of adrenalectomized rats was prevented. Rats given 100 μg/day of aldosterone following adrenalectomy maintained a continued rise of blood pressure, the rate not differing significantly from that seen in rats with continuing adrenal-regeneration hypertension. Such rats did not display thymus involution, and the blood pressure response was no greater when 1 mg/day of corticosterone was added to the regimen. It is concluded that if the profile of hypertension and failure to cause thymus involution are valid criteria for establishing the identity of the hormone(s) which cause adrenal-regeneration hypertension, aldosterone appears to qualify. Some reasons for doubting the reliability of these criteria and some of the difficulties encountered in attempting to compare quantitatively the effects of endogenously secreted hormone with exogenously administered hormone are given.

Benign and malignant hypertension after adrenal enucleation in the rat. Relationship to salt intake, response to hydrochlorothiazide, and similarity to essential hypertension

Adrenal-enucleated, mononephrectomized rats given a high salt diet rapidly develop malignant hypertension, characterized by the presence of necrotizing vascular lesions in a number of organs and tissues. If a normal salt intake is provided, or if hydrochlorothiazide is given together with a high salt diet, there is, instead, the delayed onset of benign hypertension which either stabilizes or increases in intensity extremely slowly; Such animals display few, if any, pathologic vascular changes other than occasional focal glomerular hyalinization, show insignificant cardiac enlargement, and do not exhibit alterations in the serum sodium or potassium. Occasional animals behave atypically and develop malignant hypertension despite normal salt consumption, demonstrating that in susceptible rats excess salt is not essential to this disorder. Hydrochlorothiazide given to rats that imbibed distilled water postoperatively prevented hypertension entirely for 97 days, when one of eight rats developed mild hypertension and some others reached what is regarded as a prehypertensive range. It is concluded that adrenal regeneration provides a physiological milieu favorable to the development of benign hypertension, which is not, as a rule, manifest until regeneration is complete. Salt excess converts the response into one in which malignant hypertension begins during regeneration and worsens rapidly thereafter until death. The course and findings are compared with those of the benign and malignant phases of clinical essential hypertension, and the implications of the similarities are discussed.

Acute and chronic influence of diazoxide on adrenal-regeneration hypertension

The antihypertensive activity of diazoxide was evaluated in rats with regenerating adrenal glands. The drug was given chronically in the drinking fluid, and also by subcutaneous injection at two intervals during the experiment. For a brief period diazoxide in the drinking fluid was replaced by hydrochlorothiazide. Diazoxide caused detectable sodium retention, despite which it reduced the intensity of hypertension and reduced the incidence, severity, and extent of the accompanying vascular lesions. The substitution of hydrochlorothiazide for diazoxide, or the subcutaneous administration of diazoxide to rats that were then consuming it in the drinking fluid, usually further depressed the blood pressure. It may thus be concluded that maximal blood pressure lowering effects of diazoxide were not achieved by oral ingestion, and that while the drug does afford a significant degree of protection against adrenal-regeneration hypertension it is less effective in this respect than hydrochlorothiazide, possibly because diazoxide causes sodium retention whereas hydrochlorothiazide promotes saluresis.

The comparative hypertensive activities of the acetates of D-aldosterone and deoxycorticosterone

The hypertensive effect of the acetates of d-aldosterone and deoxycorticosterone was compared by injecting 0.125 mg of each twice daily in oil subcutaneously into unilaterally nephrectomized rats given 1% saline solution to drink. The two hormones had entirely comparable activity in respect to the enhancement of saline consumption, the development of hypertension and the magnitude of cardiac enlargement induced. Aldosterone treatment caused a much greater degree of renal hypertrophy and far more severe vascular lesions in the heart and kidney. It is suggested that both of these effects may reflect the superior ability of aldosterone to cause potassium excretion and therefore a more severe hypokaliaemia. Only aldosterone caused thymic involution, believed to be an indirect response, and impairment of body growth.

Under the circumstances of this experiment the hypertensive potency of aldosterone was at least as great as that of deoxycorticosterone, and the ability to bring about vascular damage far greater. Although it is recognized that this relationship might not obtain at all dose levels of the two steroids, it is suggested that the lesser activity usually ascribed to aldosterone as compared with DCA when the two are given in dosages calculated to cause an equivalent degree of sodium retention, may reflect the operation of variables such as absorption rate, enzymatic inactivation rate and hence the respective quantities in the circulation at any given time, rather than differences in the inherent potency.

Hypertension following subcutaneous and intraperitoneal injections of polyvinyl alcohol and the effect of aldosterone

Rats given subcutaneous or intraperitoneal injections of polyvinyl alcohol (PVA) for a month developed hypertension after discontinuance of injections. Aldosterone given for a week terminally to severely hypertensive animals neither exacerbated hypertension nor induced the eclamptic manifestations previously noted to occur after more prolonged subcutaneous PVA administration. It is concluded that eclamptic manifestations are not due to increased levels of endogenous salt-retaining steroids. Possible reasons are considered for the customary inability of rats given PVA intraperitoneally to develop hypertension during the course of injections although they readily do so thereafter.Intraperitoneal PVA administration caused the formation of medial and intimal foam cells in cardiac arteries, and an abundant display of giant cells in various organs and tissues. In contradistinction to the earlier findings in animals killed immediately after a course of injections, there was in this study, in which the rats were killed only when a considerable time had elapsed after PVA treatment, no substantial difference in the severity of hepatosplenomegaly between intraperitoneally and subcutaneously injected rats.

Categories of parabiotic intoxication: further evidence that the condition results from unequal cross transfusion

Hematologic studies of parabiotic rats indicate that in addition to pairs in which one twin exhibits anemia and the partner hyperemia (parabiosis intoxication), there are pairs in which an anemic or a hyperemic rat has a normal co-twin. The hematologic status of parabionts cannot accurately be deduced from their coloration, and hence visual categorization of pairs as normal or ‘intoxicated’ is unreliable. Death of one of the partners always causes a fatal anemia to develop in the previously normal twin in healthy pairs, and usually produces the same condition in the previously erythremic partner in intoxicated pairs. The findings are interpreted to mean that the hematologic inequalities of intoxicated pairs represents the effect of unequal transfusion, with one partner gaining blood at the expense of the other; and are thought to be inconsistent with the contention that the anemia of parabiosis intoxication is hemolytic in nature and the erythremia a sludging of erythrocytes resulting in interference with their negotiation of the capillary anastomosis.