Administration Of DOCA Research Articles

The effect of 5 alpha-dihydrocortisol on the blood pressure of rats treated with deoxycorticosterone acetate and salt.

5 alpha-dihydrocortisol has been reported to amplify the mineralocorticoid activity of aldosterone. In this study 5 alpha-dihydrocortisol was administered to unilaterally nephrectomized rats treated with 11-deoxcorticosterone acetate (DOCA) and sodium chloride to examine its potentiating effect on the elevation of blood pressure in these animals. Subcutaneous administration of DOCA at two dose levels (40 microgram and 100 microgram/100 g of body weight 3 times a week) resulted in a significant rise in blood pressure when compared with controls given no DOCA. However, concomitaut injection of 5 alpha-dihydrocortisol (300 microgram/100 g of body weight 3 times a week) with both doses of DOCA did not accelerate the development or potentiate the severity of the hypertension in a 4 week period. Furthermore, administration of 5 alpha-dihydrocortisol did not cause a further decrease in plasma renin activity or a greater increase in urinary kallikrein excretion than those observed after DOCA alone. Thus, 5 alpha-dihydrocortisol does not potentiate DOCA in the production of low renin hypertension in unilaterally nephrectomized salt-loaded rats.

Sodium-chloride-induced protection in nephrotoxic acute renal failure: Independence from renin

It has been shown that the severity of experimentally induced acute renal failure (ARF) is inversely related to dietary sodium chloride intake, and the effects have been attributed to the concurrent changes in renal renin. In the current study, renal renin of rats was increased by chronic sodium deprivation and decreased by chronic sodium loading and DOCA administration. In two nephrotoxic models (mercuric chloride, uranyl nitrate), giving previously sodium-deprived rats 1% sodium chloride to drink for 48 hours prior to ARF induction greatly attenuated the severity without any reduction in their high renal renin. Conversely, giving previously sodium-loaded rats tap water to drink for 4 to 5 days prior to AFR induction greatly enhanced the severity without any increase in their subnormal renal renin. Therefore, the changes in severity of ARF resulting from changes in dietary sodium are not mediated by changes in renal renin. Significant inverse correlations were found between mean peak BUN values during the follow-up period (5 to 7 days) and the 24-hour urinary sodium excretions prior to ARF induction in both models, suggesting that sodium intake and/or excretion at the time of induction is a good predictor of the severity. The effects of sodium chloride in both models were predominantly expressed during the maintenance phase, and consisted of attenuation of the severity (both models) and hastening of the recovery (mercuric chloride model). Possible mechanisms by which dietary sodium produced its effects, independently of its effects on the renin-angiotensin system, are discussed.

Noradrenaline storage in deoxycorticosterone—saline hypertensive rats

Accumulation of labeled noradrenaline ( 3H-NA) in heart slices provided a measure of the storage ability of peripheral adrenergic nerves in rats made hypertensive by DOCA and salt (NaCl) administration. Measurements of dopamine-β-hydroxylase (DBH) and the irreversible binding of tritiated reserpine ( 3H-R) in the heart and mesenteric arteries were taken as indices of the density of storage vesicles in nerve endings. The turnover of transmitter in peripheral adrenergic nerves was estimated by measuring the disappearance of NA after blockade of its synthesis. The storage of 3H-NA in heart slices, measured by the retention of amine, was not changed during the development and maintenance phases of DOCA hypertension in the rat. DBH activity (31. 1 nmole of synephrine formed/g of heart and 193.7 nmole./g of mesenteric artery) and the binding of 3H-reserpine (4.4 ng/g/heart and 4.7 ng/g of mesenteric artery) were similar to the values observed in tissues of normotensive rats. Turnover of NA was significantly accelerated in the cardiac nerves of DOCA hypertensive rats (T 1 2 6.2 h vs. 11.7 h for controls). These results show that the storage function and the density of synaptic vesicles are not changed in the peripheral adrenergic nerves of DOCA hypertensive rats. The faster disappearance of endogenous NA or exogenous labeled NA observed in vivo in hypertensive rats may be attributed to an increased release due to enhancement of nerve impulse flow, not to an impaired storage ability.

Effects of potassium depletion on renal tubular chloride transport in the rat

Potassium depletion (KD) causes renal chloride-wasting. To investigate the effects of KD on renal tubular reabsorption of chloride, balance, clearance, micropuncture, and microinjection studies were performed on potassium-depleted rats. KD was produced by omitting potassium from the diet and by administration of DOCA on days 2 and 3; rats were studied on days 9 to 12. Diets were chloride-free in both control and KD groups. In the KD group, balance experiments confirmed greater chloride depletion and continued chloride-wasting, and clearance studies showed an increased FECl. Muscle potassium was reduced by 27% as compared to control. Whole kidney and single nephron GFR were reduced in KD rats to 72 and 74% of control. Fractional (6 +/- 6% vs. 22 +/- 4%, P less than 0.05) and absolute chloride reabsorption in the proximal tubule was not different. Fractional reabsorption of delivered chloride was reduced in the loop of Henle (92 +/- 0.8% in KD vs. 95 +/- 0.7% in control, P less than 0.02). Transtubular chloride ratio (0.28 +/- 0.02 vs. 0.21 +/- 0.02, P less than 0.02) was increased at the early distal tubule. Fractional delivery of chloride (8 +/- 0.9 vs. 5 +/- 0.5%, P less than 0.02), and fluid (26 +/- 1 vs. 22 +/- 1%, P less than 0.05) were also increased in KD at the early distal tubule. Recovery of chloride 36 injected into late distal tubules was 88 +/- 1% on a normal chloride intake, 62 +/- 2% in chloride depletion, and 88 +/- 2% in potassium and chloride depletion. Thus, KD depresses chloride reabsorption in the proximal tubule and in the loop of Henle, and it decreases chloride 36 efflux from the collecting duct.

Hemodynamic changes induced by prolonged NaCl and DOCA administration in spontaneously hypertensive rats.

The results of this study demonstrate that the spontaneously hypertensive rat is sensitive to salt excess. The hypertensinogenic effect of salt was mediated through elevation of peripheral vascular resistance. The addition of DOCA aggravated the hypertension, mainly be elevating the cardiac output without appreciably decreasing peripheral vascular resistance. SHR'S EXPOSED TO 1% NaCl consumed more fluids and excreted more sodium and urine than control rats. Those exposed to 1% NaCl and DOCA had higher fluid consumptions and excreted more sodium than the other two groups. These effects of sodium in a neurogenic strain of hypertensive rats suggest a possible interplay between the neurogenic and salt-dependent components in the development and maintenance of hypertension. They also suggest that SHRs, like other hypertensive rat models, are salt sensitive.

What makes the renin-angiotensin system a pathogenic factor?

Three types of renal hypertension in the rat have been compared with respect to blood pressure increase, activity of the RAS, and secretion of aldosterone and corticosterone: type I - unilateral stenosis of the renal artery in the presence of an intact contralateral kidney; type II - unilateral stenosis of the renal artery after contralateral nephrectomy; type III - bilateral stenosis of the renal arteries. Blood pressure rose more rapidly and reached higher values in type II and type III hypertension than in type I hypertension. In the latter group, the activity of the RAS was more stimulated than in types II and III. The marked stimulation of the RAS in type I hypertension is ascribed to the negative fluid and sodium balance, which is the consequence of a pressure-induced diuresis of the unclamped contralateral kidney. Suppression of the activity of the RAS by a 4-week pretreatment with DOC-TMA and saline or by the administration of DOCA and saline as from the induction of renal artery stenosis did not prevent the development of hypertension caused by the clamping of one renal artery (type I). In spontaneously hypertensive rats of the stroke-prone substrain, high dietary salt intake caused higher blood pressure values and a higher incidence of cerebral lesions than normal dietary salt intake. Low salt intake was followed by a marked stimulation of the RAS, but blood pressure rose only slightly and no symptoms of cerebrovascular lesions were observed. It is concluded that neither in hypertension induced by renal artery stenosis nor in spontaneously hypertensive rats, the RAS contributes significantly to the increase in blood pressure nor does it play a major part in the pathogenesis of vascular lesions. These seem to be related to the retention of sodium, which may be obtained by renal artery stenosis, by excessive salt intake, or by the administration of a mineralocorticoid and salt.

Propranolol induces acute natriuresis by beta blockade and dopaminergic stimulation.

dl-Propranolol (0.8-1.6 mg/kg - h for 1 h) produced a transient two- to three-fold increase in sodium excretion in nondiuretic rats infused with Pitressin and aldosterone and in water diuretic rats. Sodium excretion increased more in rats depleted of renin by chronic Doca and salt administration than in rats maintained on a low salt diet. An angiotensin inhibitor (1,sarcosine-8,valine angiotensin II) decreased sodium excretion. Therefore the natriuresis was not mediated by antidiuretic hormone, aldosterone, or renin-angiotensin. d-Propranolol did not produce a natriuresis. Prior treatment with phenoxybenzamine did not prevent the natriuretic response but chlorisondamine pretreatment did. The natriuresis is produced by beta blockade and requires post ganglionic nerve function but is independent of alpha receptors. dl-Propranolol decreased heart rate and cardiac output but systemic pressure did not fall and renal blood flow increased. This suggests a dopamine-mediated renal vasodilation and natriuresis. Haloperidol and pimozide, both dopamine blocking agents with minimal beta blocking effects, prevented the natriuretic response. We conclude that propranolol may increase sodium excretion directly by blocking beta receptors in the distal nephron and indirectly by dopamine-mediated renal vasodilation.

Renal hemodynamics and water excretion in Addison's disease

Patients with Addison's disease have impaired ability to excrete free water. The mechanism of this defect is still not clear. These experiments were designed to help clarify the role of altered renal hemodynamics in the genesis of the defect. Six patients with Addison's disease were studied. Enough salt and water was administered to maintain adequate hydration throughout the study but no hormonal replacement was instituted. After a water load, the urine output (V), free water clearance (C H 2O ), sodium excretion (U NaV), total solute clearance (C Osm), inulin clearance (C ln), and para-aminohippurate clearance (C PAH) were measured by standard clearance techniques. In the control studies V and C H 2O were abnormally low. The studies were repeated after administration of DOCA, 2.5 mg daily, for a week. This medication decreased U NaV and improved the plasma electrolyte profile but did not cause a significant change in V, C H 2O , GFR, or RPF. The same studies were repeated once more after administration of prednisone, 5 mg daily in divided doses, for a week. This drug induced a marked water diuresis while GFR and RPF remained unchanged. It is concluded that hypovolemia and altered renal hemodynamics are not the only mechanisms of the impaired water excretion in Addison's disease. A severe defect remains after normalization of hypovolemia and this is corrected by prednisone but not by DOCA, through mechanisms which do not involve changes in GFR or RPF.

Impaired urinary acidification in the hypothyroid rat.

Since abnormalities in the renal handling of sodium and water in both the proximal and distal tubule have been described in primary hypothyroidism, this study was undertaken to examine renal tubular hydrogen secretion in this disorder. Metabolic acidosis was induced in hypothyroid rats (H) and their age matched controls (C) by the administration of an oral ammonium chloride load of 0.15 g/24 h/kg for three days. On day 3 animals were prepared for clearance and acid-base studies, receiving an infusion of Ringer's solution of 0.6 ml/hr/100 g during surgery and the experimental procedure. A 26% decrease in GFR (P less than 0.005) and a doubling in fractional excretion of sodium (P less than 0.02) were observed in H rats. The lowest blood pH and average bicarbonate concentration and the excretion of chloride were similar in the two groups, indicating that the acid load was reabsorbed and led to similar degrees of systemic acidification. Urine flow also was comparable in the two groups. Minimal urine pH after NH4Cl was 6.21 +/- 0.06 in H and 5.68 +/- 0.09 in C (P less than 0.001). Ammonium excretion was 28% (P less than 0.05) lower in H than in C. The defect in urine acidification in H was only partially corrected after 5 days on a low sodium diet and DOCA administration for 2 days. Fractional bicarbonate excretion at normal blood pH and bicarbonate concentration was not different in the two groups. These data indicate that hypothyroid rats have a mild defect in urine acidification and that it is localized predominantly in the distal tubule.

Separate roles of sodium ion concentration and fluid volumes in salt-loading hypertension in sheep.

The goal of these studies was to determine whether the hypertension caused by excessive salt loading results from sodium-induced expansion of the extracellular fluid volume or whether the salt increases the pressure in some other way, such as by causing vascular constriction. In one group of sheep, a combination of total nephrectomy and hemodialysis was used to produce and maintain step increases in extracellular fluid volume for 1 wk without a significant change in sodium ion concentration. In a 2nd group, unilateral nephrectomy, dialysis, and DOCA administration were used to cause step increases in sodium ion concentration while the extracellular fluid volume was held as close to normal as possible. The results showed a 41% increase in arterial pressure in the high-volume sheep and only a 4% increase in pressure in the high-sodium sheep. In both instances the total exchangeable sodium increased almost equally--a 21% increase in the high-sodium sheep. The data support the concept that sodium retention causes hypertension almost entirely because of sodium-induced expansion of the extracellular fluid volume.

THE EFFECT OF ANGIOTENSIN INFUSION, SODIUM LOADING AND SODIUM RESTRICTION ON THE RENAL AND CARDIAC ADRENERGIC NERVES

The renal and cardiac adrenergic nerve patterns in rats infused with large and small amounts of angiotensin and in rats given NaCl plus DOCA, NaCl alone, and salt-free diets were examined by the histochemical fluorescence method. Infusion of small amounts of angiotensin led to a persistent blood pressure elevation whereas infusion of large amounts of angiotensin resulted in a transient rise in blood pressure, probably due to the development of tachyphylaxis. Nerve patterns were found to be normal in angiotensin-infused rats and in rats given NaCl. In rats given NaCl plus DOCA and in rats subjected to salt restriction, a partial or complete disappearance of the transmitter of the adrenergic nerve terminals were recorded. The findings suggest that angiotensin in itself is incapable of inducing visible alterations in the transmitter content of the terminals. The findings agree with the view that angiotensin potentiates a norepinephrine depletion of the terminals during sympathetic activity, since it can be assumed that increased plasma angiotensin levels as well as various degrees of increased sympathetic tonus were present in the rats subjected to salt restriction. The similar effect on the nerve terminals produced by the combined NaCl and DOCA administration is consistent with earlier reports of an increased turnover of norepinephrine in animals thus treated.

The action of arachidonic acid on experimental hyper-tension in the rat

Keeping in mind the vasodilator action of prostaglandins, the control that they exercise over the vascular supply of kidneys and the sympathetic activity, research was conducted in order to establish the effect of arachidonic acid, the precursor of PGE2, on experimental hypertension in the rat. The experimental hypertension was induced by unilateral nephrectomy, followed by the administration of DOCA and the elevated sodium diet. The treatment was short in one group, long in the other, and both groups were compared to a control hypertensive group which received no treatment at all. Arachidonic acid worsened the experimental hypertension by 37% in the long treatment, and by 25% in the short treatment. The administration of lysine-acetylsalicylate diminished this hypertension. A non-saturated acid, oleic acid, which is not involved in prostaglandin synthesis, has no action. The authors would like to emphasize that in one of the previous experiments, L-tyrosine, the precursor of catecholamines, diminished the experimental hypertension in the rat, and also that L-DOPA and IMAO (MAOI) have comparable effects. It seems, therefore, that the depression of the central catecholaminergic activity, which is supposed to be the action of arachidonic acid via an increase in the PGE2 synthesis, appears to increase hypertension. It is noteworthy that the medial forebrain bundle (MFB) is catecholaminergic and that the periventricular system (PVS) is cholinergic. Thus hypertension may represent the peripheral vascular response to anguish which results from the activation of PVS and from the depression of MFB.

Hypertension following adrenal enucleation and its absence during desoxycorticosterone treatment in Long-Evans rats.

The administration of DOCA to unilaterally nephrectomized rats given a high NaCl intake caused an intense saline polydipsia and induced hypertensive vascular disease accompanied by cardiac hypertrophy in Sprague—Dawley animals. Similarly treated Long—Evans rats developed none of these changes, although they readily developed them when subjected to enucleation of the adrenal glands. These findings would seem to be incompatible with the assumption that adrenal—regeneration hypertension (ARH) is due to endogenous DOC hypersecretion by enucleate adrenal glands. The possibility is moot: evidence both for and against such an altered steroid secretory pattern has been presented from other laboratories. If so, it may well contribute to the response, but in view of the observation that Long—Evans rats are highly refractory to the development of DOCA hypertension but highly susceptible to ARH, it can hardly be held solely responsible. (Endocrinology 92: 1175, 1973)

Glomerulotubular balance in dogs with chronic salt retention.

The relationship between changes in GFR and sodium and water reabsorption by the proximal tubule was studied in 11 control dogs and 8 dogs with salt retention produced by 5 days of DOCA administration. Fractional reabsorption by the proximal tubule was determined by recollection micropuncture before and after aortic constriction. Constriction produced significant and similar decreases in renal perfusion pressure, GFR, and RPF in control dogs and dogs with salt retention. Fractional reabsorption by the proximal tubule was significantly increased following constriction in control dogs but not in dogs with salt retention. The difference between the two groups was significant, P < 0.001. Plasma renin activity was significantly lower in dogs with salt retention before and after constriction, however, the percent increase in plasma renin activity after constriction was not different between the two groups. It is concluded that changes in GFR are accompanied by proportionate changes in reabsorption by the proximal tubule in dogs with salt retention.

Studies on the pathogenesis of hypertensive vascular disease. Effect of high-pressure intra-arterial injections in rats.

Repeated high-pressure injection of saline into the arterial system via carotid cannula in normal, ether-anesthetized rats has been previously shown to produce acute necrotizing lesions in the renal vasculature. In this study administration of the vasodilator aminophylline prior to high-pressure injections led to similar lesions, produced in dilated, hyperdistended vessels, at far lower pressures than in control animals, demonstrating that neither vasoconstriction nor the absolute height of blood pressure is a critical determinant in production of lesions. In the second part of the study previous treatment with desoxycorticosterone (DOCA)-saline for 12 to 18 days rendered the renal vasculature abnormally prone to lesions after high-pressure injections, compared with normal rats so injected or those receiving a DOCA-saline regimen only. Glomerular lesions were more severe than can be explained on the basis of simple addition of the lesions resulting from high-pressure injections to those arising from DOCA administration. This increased susceptibility of the vasculature to elevated pressure is probably a function of focal alteration of vascular smooth muscle. These observations support the proposal that hypertensive vascular lesions occur in dilated, hyperdistended vessels and the glomeruli distal to them, the dilatation probably resulting from focal smooth muscle alteration with partial or complete loss of contractility.

KARYOMETRIC STUDIES ON THE REACTIVITY OF THE ADRENAL CORTEX OF NEWBORN RATS

ABSTRACT Karyometric studies of cell nuclei in the zona glomerulosa and zona fasciculata of the rat adrenal cortex were carried out on the 1st to the 7th day of life following single administration of formalin, electric shock, ACTH, DOCA, cortisol and adrenaline. A formalin injection, given on the day of birth, evoked a rise in the volume of adrenocortical nuclei even in the group of rats two days old. This indicates that there is already a functionally active pituitary-adrenal axis in the early postnatal period. The response to formalin stress or to the administration of ACTH, DOCA and cortisol is similar in both adrenocortical zones, i. e. in zona glomerulosa and the zona fasciculata during the first four days of postnatal life. This may be connected with a low degree of differentiation of both zones. Starting with the 5th day, a differentiated response to exogenous stimuli in the individual zones, similar to that in adult animals was found.

Evidence for a humoral factor modifying the renal response to blood volume expansion in the rat.

In this study, designed to examine the interaction of mechanisms regulating renin secretion with those producing "volume diuresis and natriuresis", rats depleted of renin by chronic salt-loading and desoxycorticosterone (DOCA) administration (DOCA rats) showed exaggerated responses to iso-oncotic blood volume expansion. Conversely, chronically salt-deficient rats (NaD rats), known to have high renin levels, showed very depressed responses to expansion. Isovolemic cross-circulation of DOCA and NaD rats, including exchange of the animals' blood with bovine albumin solution in a reservoir, largely restored the renal response of NaD rats to subsequent infusion from the reservoir without altering responsiveness of the DOCA rats. Changes in plasma sodium, hematocrit value, and vascular pressures following cross-circulation were not different from those which followed exchange without cross-circulation in control experiments. In the latter, the renal response of NaD rats remained depressed, a finding not altered by acute administration of DOCA. The modification of response in cross-circulated NaD rats was therefore attributed to transfer of a humoral factor which interacted with the volume regulatory mechanism. Such a factor could be anti-renin, or alternately, a humoral effector, the level of which was critically increased in NaD rats before expansion.

Cytoplasmic granularity of the renal medullary interstitial cells in experimental hypertension.

Abstract The renal medullary (papillae and medullae) interstitial cells have prominent features suggesting an actively secretory cell. These include the presence of numerous mitochondria, prominent Golgi bodies, smooth-surfaced endoplasmic reticula, and osmiophilic granules which are stained for neutral lipids with oil Red-O. The interstitial cells were studied as a possible production site for the antihypertensive factor-a neutral lipid. Experimental hypertension was induced in Sprague-Dawley rats by administration of excessive sodium chloride or by injections of DOCA or with a combination of both agents. The same agents were administered to separate groups of animals with and without unilateral nephrectomy. The granularity within 100 interstitial cells was evaluated quantitatively in 0.5 μ sections stained with methylene blue and azure II. Granules within interstitial cells were also counted in electron micrographs of 50 cells chosen at random. Hypertension developed in a significant number of animals after administration of DOCA and also after administration of saline with DOCA, in both uninephrectomized and non-nephrectomized animals. Animals were more susceptible to experimental hypertension following unilateral nephrectomy. Ultrastructural studies of the renal medullary interstitial cell in control animals revealed a relatively constant number of cytoplasmic granules (8.8 ± 1.2). In animals undergoing unilateral nephrectomy and given NaCl with DOCA, the osmiophilic granularity was significantly increased (p

Some Biochemical Effects seen after the Administration of Synthetic Adrenal Cortex Hormones to Normal Sheep

SUMMARY The effects of single intramuscular injections of either prednisolone acetate or desoxycorticosterone acetate were investigated in normal sheep. Following prednisolone administration plasma glucose concentration was significantly increased, and plasma potassium, total circulating eosinophils and packed cell volume were significantly decreased. The rate of removal of an intravenously administered glucose load was significantly reduced in a sheep pretreated with prednisolone. Following both prednisolone and DOGA administrations, significant increases in daily water intakes were recorded. Urine outputs were not significantly increased (P = 0 · 05). The only other statistically significant effects detected following DOCA administration were an increase in total circulating eosinophils and a decrease in packed cell volume.

Morphological changes in the hypothalamo-pituitary-adrenal system during early postnatal period in rats

The administration of ACTH, DOCA, hydrocortisone or formalin-induced stress on the day of birth, or during the postnatal period, causes the same reaction in the adrenal gland of neonatal rats as in adult animals. An enlargement of the adrenal cortex, and a significant increase in the nuclear volume in the fascicular zone, as well as a less pronounced increase in the glomerularzzone, was found both in the ACTH-treated animals and in those treated with formalin. Opposite changes were observed after hydrocortisone administration. DOCA, however, induced remarkable changes in both the glomerular and fascicular zones, suggesting a deerease of their function. Qualitative and quantitative changes occurred also in the so-called “hypophysiotropic area” of the hypothalamus. ACTH, DOCA, hydrocortisone, stress-induced irregularity, and atrophy of cells decreased the volume of nuclei in this area. These changes could not be observed in other regions of the hypothalamus.