Effect of mineralocorticoids on collecting duct hydrogen ion secretion in the rabbit

The purpose of this study was to elucidate the mechanism whereby a potassium infusion led to an elevation in the urine minus blood (ohm-B) PCO2 difference in alkaline urine of the rabbit. Rabbits given 9alpha-fluorohydrocortisone 16 h prior to study had a significantly high olm-B PCO2 than control rabbits. However, the ohm-B PCO2 was increased further after potassium infusion. These results suggest that the increased collecting duct hydrogen ion secretion in the rabbit may in part have been induced by mineralocorticoids and in addition been influenced by increasing the potassium concentration.

Effect of mineralocorticoid replacement therapy on renal acid-base homeostasis in adrenalectomized patients

Chronic balance studies were performed in six adrenalectomized patients to investigate the renal and systemic acid-base consequences of mineralocorticoid deficiency in the absence of either glucocorticoid deficiency or parenchymal renal disease. Constant glucocorticoid replacement was provided with dexamethasone, 750 to 875 micrograms/day, administered orally. Creatinine clearance averaged 98 +/- 8 ml/min/1.73 m2. Following a control period, mineralocorticoid replacement with fludrocortisone (100 to 200 micrograms/day) was either discontinued (N = 3) or initiated (N = 2). In an additional patient, mineralocorticoid replacement was initiated and sustained (5 days) by continuous i.v. infusion of aldosterone, at a dose approximating the normal secretion rate (120 micrograms/day). Net acid excretion (NAE) and plasma total carbon dioxide decreased in each patient in whom mineralocorticoid was discontinued and increased in each patient in whom mineralocorticoid was initiated. The cumulative change in NAE (sigma delta NAE) independent of direction averaged 66 +/- 20 mEq (P less than 0.05) by the fifth experimental day in the six patients, and the corresponding change in plasma total CO2 averaged 1.2 +/- 0.3 mmoles/liter (P less than 0.02). The magnitude of sigma delta NAE correlated with the basal rate of NAE (r = 0.87, P less than 0.05), which averaged 0.9 +/- 0.1 mEq/kg body wt per day. The change in plasma total CO2 correlated with sigma delta NAE (r = 0.83, P less than 0.05). The changes in NAE correlated positively with the corresponding changes in sodium balance and negatively with the corresponding changes in potassium balance. These findings provide the first evidence that renal acidification is under tonic stimulation by mineralocorticoid at levels not exceeding those in normal subjects ingesting acid-producing diets of normal sodium and potassium content. The extent to which the tonic stimulation of renal acidification is mediated by a direct effect of mineralocorticoid on renal hydrogen ion transport or by an indirect effect dependent on altered renal sodium and/or potassium transport requires further investigation. The findings implicate mineralocorticoid deficiency as a significant renal acidosis-producing condition not dependent on the presence of renal disease or glucocorticoid deficiency, and potentially amplified when endogenous acid production is increased by diet or disease.

Evidence for functionally distinct pools of phospholipase responsible for prostaglandin release from the perfused guinea-pig lung

The release of prostaglandin- and thromboxane-like material from the isolated perfused guinea-pig lung was elicited by challenge with arachidonic acid, bradykinin, histamine and ovalbumin (in ovalbumin-sensitised animals), and detected by superfusion cascade bioassay. Mepacrine inhibited release to all agents except arachidonic acid. Dexamethasone and fludrocortisone inhibited release induced by histamine and anaphylactic challenge but not by bradykinin or arachidonic acid. These results suggest two functionally distinct pools of phospholipase responsible for initiating prostaglandin biosynthesis in the guinea-pig lung.

Role of the autonomic nervous system in the acute responses to renal artery pressure reduction in conscious dogs

1. Plasma renin and arterial pressure responses to acute renal artery pressure reduction were compared in intact dogs and "autonomically-blocked" dogs subjected to adrenalectomy, chronic guanethidine treatment and acute vagal block (methscopolamine). 2. Following reduction of renal artery pressure plasma renin activity and concentration rose more in the autonomically blocked dogs than in the intact dogs. When renal artery pressure was held at 30 mmHg for 1 h, plasma renin activity rose by 19.1 ng/ml per h (range 11.6-28.7) in autonomically blocked dogs and 3.65 ng/ml per h (range 1.54-5.89) in intact dogs. When renal artery pressure was held at 60 mmHg plasma renin activity rose 3.28 ng/ml per h (range 2.4-4.7) and 1.90 ng/ml per h (range 1.30-3.56), respectively. 3. Arterial blood pressure also rose more in autonomically blocked dogs in accord with the greater rise in plasma renin activity. The relationships between the increases in arterial pressure and plasma renin were closely similar in the two groups. 4. We conclude that the release of renin and increase in arterial blood pressure in response to renal artery stenosis is normally inhibited by arterial baroreflexes.

The effect of mineralocorticoid administration on urine free dopamine in man

1. Five normal subjects were studied under metabolic conditions on a controlled sodium and potassium intake. 2. Plasma and urine free dopamine concentrations were measured in these subjects before, during and after 5 days administration of fludrocortisone (0.2 mg twice daily). 3. Urine free dopamine showed a tendency to fall during the early phase of fludrocortisone administration and then rose towards normal. 4. In a patient with primary hyperaldosteronism there was no evidence of increased renal production of dopamine. Urine dopamine fell when plasma renin activity rose as a result of spironolactone administration (200 mg three times a day for 5 days). 5. If renal dopamine has a role in mineralocorticoid 'escape' then it may be permissive only. The mechanisms of control of dopamine production could include tubular sodium concentration, tubular chloride concentration and intrarenal renin activity.

[Haemodynamic studies on the blood pressure-raising effect of mineralocorticoids (author's transl)]

The effects on systemic haemodynamics of long-term administration of high mineralocorticoid doses were studied in six healthy volunteers. The subjects received the synthetic steroid fludrocortisone in a daily oral dose of 0.8 mg. Central venous and arterial pressures were recorded directly, and cardiac output was determined by dye dilution method before as well as after 1 and 6 weeks of steroid application. Within the first week of steroid administration, mean arterial pressure rose by 5.6 +/- 4.6 (+/- S.D.) mm Hg (p less than 0.025). Body weight increased by 2.5 +/- 1.1 kg (p less than 0.01), and central venous pressure by 1.3 +/- 1.4 mm Hg (p less than 0.05). An increase in cardiac index was observed in all subjects, the average increase was 0.72 +/- 0.47 1/min.m2 (p less than 0.01). Heart rate decreased. After the 6th week of steroid administration, blood pressure had risen in all subjects, the average increase in mean arterial pressure was 17.8 +/- 6.0 mm Hg (p less than 0.001). This pressure rise was the consequence of an increase in total peripheral resistance by 267 +/- 125 dyn.cm-5.s (p less than 0.01) on the average. At that time cardiac index was even lower than at the first study in five of the six subjects. Compared to the second study, heart rate had decreased further, central venous pressure had increased further, and body weight had not changed significantly. This data show that the mineralocorticoid-induced blood pressure rise is initially due to an increase in cardiac output and in its chronic phase due to an elevated peripheral resistance. The mechanism of the increase in peripheral resistance remains unclear.

Studies on mineralocorticoid 'escape' in cirrhosis

1. The mineralocorticoid 9 alpha-fluorohydrocortisone was given to 12 patients with cirrhosis without ascites. In seven an 'escape' from its sodium-retaining effects was observed, the other five continuing to retain sodium. 2. Changes in plasma renin activity (PRA) and inulin clearance (Cinulin) were used in the assessment of possible changes in the 'effective' extracellular fluid volume. PRA fell and Cinulin increased to a similar extent in each of the two groups of patients. The findings do not support the concept that the failure to show the mineralocorticoid escape in some patients with cirrhosis is due to a failure of expansion of the effective extracellular fluid volume. 3. Sodium reabsorption in the different segments of the nephron as estimated by clearance techniques under conditions of maximal water diuresis showed that the greatest changes to account for both mineralocorticoid escape and sodium retention were in the part of the nephron beyond the diluting segment.

Hypertension with mineralocorticoid administration to the Long-Evans rat

1. The Carworth Long-Evans rat has been reported to develop adrenal-regeneration hypertension but not deoxycorticosterone acetate (DOCA) hypertension. Deficiency of a hypothalamic receptor for deoxycorticosterone which mediates saline polydipsia has been postulated to underlie this resistance. Since a mineralocorticoid etiology for adrenal-regeneration hypertension has been postulated and all mineralocorticoids are thought to act on common receptors, these previous reports are difficult to reconcile. 2. To determine if an absolute or relative resistance to mineralocorticoids is present, Charles River Long-Evans and Sprague-Dawley rats were given 40 mg (107 micromol) of DOCA pellets/rat or 250 microgrms (0.65 micromol) of 2 alpha-methyl-9-alpha-fluorocortisol/day subcutaneously. 3. Saline polydipsia occurred with both steroids with both rat strains, though significantly less with the Long-Evans rats. Both types of rats became hypertensive and developed cardiac and renal enlargement with both steroids. Hypertension developed more rapidly with 2 alpha-methyl-9 alpha-fluorocortisol. 4. Thus mineralocorticoid hypertension can be produced in the Charles River Long-Evans rat, and the development of adrenal-regeneration hypertension in this rat strain is not incompatible with a mineralocorticoid etiology for adrenal-regeneration hypertension.

Primary aldosteronism: inability to differentiate unilateral from bilateral adrenal lesions by various routine clinical and laboratory data and by peripheral plasma aldosterone

In 31 patients with primary aldosteronism routine clinical and laboratory data, the effect of orthostasis on plasma aldosterone (PA), plasma renin activity (PRA) and cortisol (PC), effect of fludrocortisone or high sodium intake on basal PA and night-day fluctuations of basal PA and PC with and without suppression of pituitary ACTH by dexamethasone were determined to differentiate patients with a unilateral aldosterone producing tumour (adenoma, APA, n=20; carcinoma, CA, n=1) from those with idiopathic bilateral adrenal hyperplasia (IAH, n=10). Mean systolic and diastolic blood pressure, age, serum potassium and urinary excretion of sodium and potassium were not significantly different in both groups of patients. Normokalaemic primary aldosteronism occurred both in patients with APA (n=2) and in patients with IAH (n=1). Mean basal PA and mean urinary excretion rate of aldosterone-18-glucuronide were higher though not significantly different in patients with APA or CA than in those with IAH. A substantial number of the patients with APA (n=5) and with IAH (n=3) showed urinary excretion rates of aldosterone-18-glucuronide less than 13 microgram/24 h. Mean PA and PRA significantly increased (P less than 0.025) in patients with IAH in response to posture. However, these changes also occurred at times in some patients with APA. Both fludrocortisone and high sodium intake produced a variable and no group-specific effect on basal PA. Night-day variations in PA were positively correlated with those in PC in all patients with APA (n=12) and in 5 of 8 patients with IAH. A dissociation of PA and PC, however, was only observed in patients with IAH. Finally, the effect of dexamethasone on plasma aldosterone curves was variable in both groups of patients. Our results indicate that under the described conditions analysis of routine clinical and laboratory data and of peripheral PA, PRA and PC are of limited value in differentiating patients with APA or CA from those with IAH.

[The action of 9 alpha-fluorohydrocortisone on some aspects of water-electrolyte metabolism in animals]

This mineralocorticoid effect of different doses of the synthetic hormone 9-alpha-fluorhydrocortisone was studied. The introduction of the drug to intact animals per os was found not to produce any sodium-retention effect. A single adminstration of 9-alpha-fluorhydrocortisone causes an intensified excretion of water, sodium potassium with the urine. A course-wise application of the hormone brings about the development of hypokaliemia.

The effects of aspirin, ethanol, indomethacin and 9alpha-fludrocortisone on buccal mucosal potential difference

1 Measurement of the bioelectric potential of the buccal mucosa has been made in three areas, namely on the lower lip between lip and gum, on the sublingual papilla, and at the entrance to the parotid duct.

2 The charge on the buccal mucosa (or buccal potential difference (b.p.d.)) was found to be negative with respect to a saline-injected area of skin. One hundred and eighty measurements of b.p.d. in thirty subjects demonstrated a normal distribution. B.p.d. was unchanged by stimulation of salivary flow, but was reduced or reversed in polarity over areas of aphthous ulceration. B.p.d. was reduced significantly by treatment of the mucosa with deionized water at 65°C, but not by deionized water at 20°C. A characteristic mucosal pressure artifact was demonstrated in response to an increased force applied to the mucosa through the electrode.

3 No response in salivary electrolytes, electrode measured buccal electrolytes or b.p.d. was observed after treatment with 9α-fludrocortisone. Local application of aspirin and ethanol reduced b.p.d., their effects being additive. Local application of indomethacin and deionized water produced no significant change in b.p.d. These responses to aspirin, indomethacin and ethanol are similar to the responses of gastric transmural p.d. to these agents.

4 There appear to be basic similarities in the responses of transepithelial p.d. in different areas of the upper gastrointestinal tract to agents generally regarded as damaging to mucosa.

Rectal potential difference and histology in Crohn's disease

The rectal potential difference (PD) was measured in 27 patients with Crohn's disease, and in 16 subjects without gastrointestinal disease to establish a normal range. Sigmoidoscopic assessment and rectal biopsy were performed in all patients with Crohn's disease, and the mean resting rectal PD was significantly reduced in patients with sigmoidoscopically active disease and in those with abnormalities of the superficial epithelium on rectal biopsy. Patients with diarrhoea had a significantly lower mean resting PD than those with normal bowel habit, suggesting that an abnormality of rectal sodium transport may be contributing to the diarrhoea in these patients. The response of rectal PD to mineralocorticoid stimulation with oral fludrocortisone was measured in 13 patients. The PD failed to rise only with patients with sigmoidoscopically active disease, and the test proved to be a less sensitive indication of minor mucosal abnormalities than sigmoidoscopy of biopsy.

Impaired renal tubular potassium secretion in systemic lupus erythematosus

Two patients with long-standing systemic lupus erythematosus were found to have persistent hyperkalemia. The hyperkalemia could not be explained by renal insufficiency, oliguria, diminished distal sodium delivery, acidemia, or hemolysis. After sodium depletion, urinary aldosterone excretion and plasma aldosterone concentration rose appropriately. No increase in urinary potassium excretion or decrease in serum potassium concentration was noted after fludrocortisone acetate, furosemide, or acetazolamide plus sodium bicarbonate. We conclude that these patients have a primary defect in renal tubular potassium secretion that may be related to an immune complex interstitial nephritis.

Glucocorticoid and mineralocorticoid actions on gastric secretion in man

The effects of a 6-day course of treatment with a glucocorticoid (prednisolone, 1 g per day i.v.), a mineralocorticoid (9-alpha-fluorohydrocortisone, 0.3 mg per day orraly), or both the drugs on gastric secretion of acid, protein, pepsin, and N-acetylneuraminic acid (NANA) containing glycoproteins were investigated in 22 volunteers. None of the treatments produced any statistically significant changes in gastric secretion of aggressive factors, acid and pepsin. However, the output of protective NANA bound to glycoproteins was found to be decreased following prednisolone. The prednisolone effect was not prevented by 9-alpha-fluorhydrocortisone given concomitantly. Gastroduodenoscopy did not reveal any lesions attributable to drug adminstration.

Diurnal pattern of water and electrolyte excretion and body weight in idiopathic orthostatic hypotension. The effect of three treatments

The diurnal pattern of water and solute excretion and body weight were examined in five control subjects and in a patient with idiopathic orthostatic hypotension before and during treatment. The patient had a reversed diurnal pattern of excretion of sodium, urea and water but not of potassium and creatinine, and there was an excessive diurnal variation in body weight. The effects of three treatments, high salt diet alone and then with the addition of head-up tilt, and later fludrocortisone, were studied. Fludrocortisone caused marked clinical improvement and retention of sodium and water. Once a steady state was achieved none of the treatments had any significant effect either on the diurnal variation in weight or on the water and solute xcretion pattern except for a small reduction in sodium excretion at night when the patient slept with a head-up tilt. In is concluded that these treatments cause symptomatic improvement in idiopathic orthostatic hypotension through an increase in extracellular fluid volume rather than through any change in the abnormal diurnal pattern of water and salt excretion.

Repeated circadian growth hormone, luteinizing hormone, and follicle-stimulating hormone in children: influence of 9-alpha-fluorohydrocortisone

Growth hormone (GH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) in plasma of 5 children at different pubertal stages and suffering from moderate orthostatic complaints, were measured by radioimmunoassay (RIA). Parameters for secretory capacity were arginine loading and circadian hormonal patterns in hourly intervals from 8 a.m. to 8 p.m. and in half-hourly intervals from 8 p.m. to 8 a.m. before and after 6 weeks treatment with 9-alpha-fluorohydrocortisone (9-alpha-F, Astonin-H, Fa. Merck, Darmstadt, 0.1--0.2 mg/day. Plasma GH during arginine tests and in circadian levels remained unchanged, but circadian LH showed a consistent slight rise in all children. With pubertal development, magnitude and timing of GH peaks increased in boys, and rather decreased in the two girls toward late puberty. Episodic fluctuation of LH and FSH were more marked during sleep, and increased in the three bosy as puberty advanced. Similar intraindividual patterns for GH and LH, but not for FSH were noted in 4 children. Timing of GH and LH peaks appeared to be correlated. An intrinsic hereditary long-term regulatory principle is discussed.

Relationships among urinary kallikrein, mineralocorticoids and human hypertensive disease

Urinary kallikrein excretion is reduced in patients with hypertension of unknown etiology. In addition, the excretion of this renal, kinin-forming enzyme was found to be elevated in hypertensive patients with primary aldosteronism. Aldosterone regulates kallikrein excretion, as normal subjects show increased kallikrein excretion in response to a low sodium intake, high potassium intake, or the synthetic mineralocorticoid, fludrocortisone, whereas kallikrein excretion falls during treatment with spironolactone. The relationship between kallikrein excretion and aldosterone activity may directly reflect the intrarenal activity of the kallikrein-kinin system, as determined by studies of kallikrein levels from isolated renal cells or of plasma kinin levels in man in response to postural changes or saline loads. Some patients with essential hypertension do not show a normal increase in kallikrein excretion in response to low dietary sodium intake despite an apparently normal aldosterone response, suggesting that there may be a defect in the renal kallikrein-kinin system in these patients. Whether these findings are of pathogenetic significance in human hypertensive disease remains to be determined.