Effect of prostaglandin inhibition on the hypertensive action of sodium-retaining steroids

Effect of Synthetic Corticosteroids on Vascular Reactivity in the Human Forearm

Exogenous cortisol raises blood pressure (BP) and suppresses acetylcholine (ACh)-induced vasodilatation in healthy male volunteers. This study tests the hypothesis that the activation of either classical type I or II corticosteroid receptors by synthetic corticosteroids induces endothelial dysfunction. In two separate studies, dexamethasone or fludrocortisone was administered to healthy male subjects over five days. BP, metabolic parameters, and forearm blood flow (FBF) responses to intra-arterial ACh and nitroprusside (SNP) were measured on day 5 of treatment. Fludrocortisone (800 microg/day) and dexamethasone (3 mg/day) increased BP from control measurements, but not when compared with placebo. Metabolic effects of the steroids were consistent with their known actions. Endothelium-dependent vasodilatation was enhanced by fludrocortisone, most obviously in the presence of nitric oxide (NO) synthase inhibition with NG-mono-methyl-L-arginine (LNMMA). Dexamethasone did not suppress endothelium dependent or independent vasodilatation. Non-NO-mediated endothelium-dependent vasodilatation was increased by systemic mineralocorticoid excess but unaffected by glucocorticoid excess. These results do not support the notion that cortisol-induced vascular effects are mediated through classical corticosteroid receptors.

Arachidonate metabolites and serotonin contraction of femoral arteries from DOCA-salt hypertensive rats

Serotonin stimulates phospholipase A(2)(PLA(2)) leading to the production of prostaglandin products, several of which are vasoconstrictors. We hypothesised that the elevated vascular responsiveness to serotonin in deoxycorticosterone acetate (DOCA)-hypertensive rats is due in part to augmented production of vasoconstrictor cyclooxygenase products (e.g. PGF(2)alpha). Denuded helical strips of femoral arteries from DOCA-salt hypertensive rats (SBP 183 +/- 7 mmHg) and normotensive control rats (SBP 115 +/- 2) were used in all experiments. EC(50) values for several agonists were significantly reduced in DOCA arteries compared with controls (in mu mol/L, control vs. DOCA): PGF(2)alpha (0.99 vs. 0.23), PGE(2) (0.72 vs. 0.22), arachidonate (1.52 vs. 0.73), serotonin (0.19 vs. 0.07), noradrenaline (0.029 vs. 0.013), KCl (40.1 vs. 27.0 mmol/L) and AlF(4) (2.3 vs. 1.4 mmol/L). Treatment with indomethacin (14 mu mol/L) inhibited the responses to serotonin in DOCA arteries (EC(50) values 0.07 untreated vs. 0.70) and eliminated the responses to arachidonate but did not affect KCl or AlF(4-)contractions. Cyclooxygenase inhibitors shifted concentration response curves to serotonin in sham and DOCA tissues equally. Thus increased sensitivity to serotonin in DOCA arteries persisted following cyclooxygenase blockade. Therefore, although arachidonate products contribute to the serotonergic contraction in femoral arteries, the augmented response in arteries from DOCA hypertensive rats is not due to increased production of or sensitivity to cyclooxygenase products. Furthermore,arachidonate metabolites do not contribute to the contraction induced by either AlF(4-)or KCl in this preparation.

Low-dose Iloprost infusion improves insulin action and non-oxidative glucose metabolism in hypertensive patients

Fourteen hypertensive (174.3/98.3 mmHg) non-diabetic patients were given a euglyceamic glucose clamp along with infusion of 0.9% NaCl and the prostacyclin (PGI2) analogue Iloprost (0.7 ng x kg x min(-1)). Substrate oxidation was also determined by indirect calorimetry. Over the last 60 min of the clamp, Iloprost vs saline improved whole body glucose disposal (WBGD) (35 vs 28.3 micromol x kg(-1) LBM) and non-oxidative glucose metabolism (24.7 vs 18.1 micromol x kg(-1) LBM x min(-1). Iloprost delivery was associated with a significant decrease in membrane microviscosity (0.253 vs 0.205), but did not affect arterial blood pressure and heart rate. In nine patients, skeletal muscle blood flow (SMBF) and insulin-stimulated glucose uptake (GU) were also studied. At the end of the study, despite a similar SMBF (37 vs 38 ml x min(-1) x kg(-1)), GU (0.55 vs 0.46 mmol x l(-1)) was significantly increased by Iloprost infusion. Percentage decrease in membrane microviscosity was correlated with percentage increase in WBGD (r = 0.65) and non-oxidative glucose metabolism (r = 0.68). In conclusion, low-dose Iloprost infusion improves insulin action and non-oxidative glucose metabolism in hypertensive patients.

Potassium supplementation ameliorates mineralocorticoid-induced sodium retention

Potassium depletion induced by dietary potassium restriction causes sodium retention while potassium supplementation augments urinary sodium excretion. The role of external potassium balance in modulating mineralocorticoid-induced sodium retention in humans is unknown. Accordingly, eight healthy subjects were studied at the Clinical Research Center receiving a constant diet providing (per kg body wt) sodium 2.5 mmol, potassium 1.1 mmol daily. After establishing basal sodium and potassium balance over three days, each subject received 9 alpha-fludrocortisone 0.4 mg/day for 10 days. Subjects were studied twice, four to eight weeks apart, in a double blind, randomized crossover design receiving either placebo or additional KCl (80 mmol/day) over the 10 day study period. Serum potassium concentrations were unchanged from basal values on KCl while the values fell (4.1 +/- 0.1 vs. 3.4 +/- 0.1 mmol/liter, P = 0.01) on placebo. Urinary sodium excretion decreased with fludrocortisone administration in both groups, but this decrease reached significance only in the placebo group. Furthermore, during fludrocortisone administration the sodium excretion rates on KCl were significantly higher compared to the values noted on placebo (134 +/- 8 vs. 112 +/- 13 mmol/day, P = 0.01). Body weight recorded after 10 days of fludrocortisone administration was higher on placebo compared to KCl (72.3 +/- 2.8 vs. 71.6 +/- 2.8 kg, P = 0.01). Plasma renin activity, and aldosterone concentrations decreased on fludrocortisone while atrial natriuretic peptide levels increased. These studies suggest that amelioration of hypokalemia attenuates mineralocorticoid-induced sodium retention. Therefore, potassium depletion may contribute to the mineralocorticoid-induced sodium retention.

Nonsteroidal anti-inflammatory drugs and antihypertensives

Approximately 60 million people in the United States have hypertension (BP greater than or equal to 140/90 mm Hg), 40 million have arthritis clinically suitable for nonsteroidal anti-inflammatory drug (NSAID) therapy, and millions take NSAIDs for nonarthritic conditions, creating considerable potential for concomitant administration of NSAIDs and antihypertensive agents. It is estimated that more than 20 million people are on concurrent therapy. Most NSAIDs produce mild elevations of normal blood pressure levels and can partially or completely antagonize the effects of many antihypertensive drugs. The effect on blood pressure can vary from no effect to hypertensive crisis. In pooled studies, the average increase in mean arterial pressure was 10 mm Hg, and duration was short-lived or chronic. Significant interactions occur in about 1% of patients per year. The risk is greatest in the elderly, blacks, and patients with low-renin hypertension. NSAIDs may block the antihypertensive effects of thiazide and loop diuretics, beta-adrenergic blockers, alpha-adrenergic blockers, and angiotensin-converting enzyme inhibitors. No interactions have been reported with centrally acting alpha agonists or the calcium channel blockers. The mechanism of the hypertensive effects of NSAIDs seem primarily related to their ability to block the cyclo-oxygenase pathway of arachidonic acid metabolism, with a resultant decrease in prostaglandin formation. The prostaglandins are important in normal modulation of renal and systemic vascular dilatation, glomerular filtration, tubular secretion of salt and water, adrenergic neurotransmission, and the renin-angiotensin-aldosterone system. Blockade of salutary effects of prostaglandins by NSAIDs results in a complex series of events culminating in attenuation of the effects of many antihypertensive agents. High-risk patients treated with NSAIDs should be identified and have blood pressure, renal function, and serum potassium frequently monitored.

A 'hypertensinogenic' class of steroid hormone activity in man?

1. Studies in sheep have led to the concept of a 'hypertensinogenic' (HT) steroid hormone activity, whereby the blood pressure (BP) raising effects of adrenocortical steroids can be separated from their in vivo glucocorticoid (GC) or mineralocorticoid (MC) activities. 2. The three main lines of evidence are as follows: (i) BP raising effects of ACTH cannot be reproduced by appropriate rates of infusion of steroids with GC and MC activities; (ii) certain steroids e.g. 9 alpha-fluorocortisol can increase BP at rates of infusion below threshold for in vivo GC or MC actions and for many steroids there is no correlation between GC, MC and HT effects; (iii) demonstration of differential antagonism of HT, MC and GC effects. 3. Studies in man show that the BP effects of ACTH are due to cortisol (F) at levels which have both MC and GC activity. However, BP effects of ACTH cannot be blocked by MC and GC antagonists. 4. Although complete separation of in vivo GC, MC and HT activities has not been possible in man, our own studies show a degree of dissociation. Taken together, these data suggest that steroids may raise BP by a HT mechanism distinct from classical in vivo MC or GC activities in man as well as sheep.

Prostanoids and aldosterone-induced mild experimental hypertension in rats

The goal of this study was to determine the role of prostanoids in a new model of mineralocorticoid-dependent hypertension induced by the subcutaneous infusion of aldosterone (1 micrograms/hr) to normal male Sprague-Dawley rats. This regimen caused a mild and gradual increase in systolic pressure over a period of 4 weeks (113 +/- 1 vs. 137 +/- 3 mm Hg) and was associated with an increase in the in vivo formation of prostaglandins I2 and E2 and of thromboxane A2 in the kidney. High sodium intake induced a fall in the urinary levels of prostaglandin E2 and a rise in the arterial pressure of control rats (126 +/- 1 vs. 113 +/- 1 mm Hg) but did not influence aldosterone-induced hypertension. Indomethacin (3.0 mg/kg/day) caused a profound inhibition of the in vivo synthesis of prostaglandin I2 and thromboxane A2 without modifying the renal production of prostaglandin E2. Although indomethacin exerted no effect on aldosterone-induced hypertension in rats fed a normal diet, it caused a further rise in systolic pressure in aldosterone-treated rats fed a high sodium diet (157 +/- 6 vs. 140 +/- 4 mm Hg). The results of this study in a model of aldosterone-induced mild hypertension in the rat indicate that 1) aldosterone exerts a stimulatory effect on the renal synthesis of prostanoid, particularly prostaglandin E2; 2) thromboxane A2 and prostaglandin I2 do not seem to play a role in aldosterone-induced hypertension under conditions of normal dietary salt intake, whereas the role of prostaglandin E2 is unclear; 3) there is enough sodium in a normal diet to allow for the maximal expression of the hypertensive effect of aldosterone; 4) prostaglandin I2 seems to play a significant role in modulating the cardiovascular impact of a high sodium diet in aldosterone-treated rats; and 5) the renal biosynthesis of prostaglandin E2 is particularly resistant to the inhibitory effect of indomethacin in vivo.

Effects of indomethacin on steroid-induced changes in pressor responsiveness in man

1. It has been shown previously that hydrocortisone (F) increases pressor responsiveness in normal subjects. The present study examined the role of vasodilator prostanoids in determining these changes. 2. Pressor responsiveness to angiotensin II (AII) (1-8 ng/kg per min) and phenylephrine (PE) (0.3-0.9 microgram/kg per min) was examined in six normal men receiving: no treatment (day 1); 100 mg indomethacin p.o. (INDO) in three divided doses over 20 h (day 2); 200 mg F for 5 days, 50 mg 6 hourly p.o. (day 6); F plus 100 mg INDO (day 7). 3. Blood pressure, body weight and plasma glucose rose with F and plasma potassium fell. F alone produced significant increases in response to AII at 2 ng/kg per min, for systolic pressure (SBP), diastolic pressure (DBP) and mean arterial pressure (MAP), and at 1 ng/kg per min for DBP. The threshold for SBP, DBP and MAP rises with AII was decreased by F. Responses to PE following F were greater at 0.6 microgram/kg per min for SBP, DBP and MAP and the threshold for all parameters fell. 4. INDO alone had no significant blood pressure or metabolic effects and no effect on the magnitude of the blood pressure rise with AII, but decreased the threshold dose for effects on MAP. INDO had no effect on the magnitude of the pressure rise with PE, but decreased the threshold dose for effects on SBP. 5. INDO did not modify responsiveness or threshold to AII following F. Responsiveness to PE was unchanged and threshold fell for SBP only during INDO.(ABSTRACT TRUNCATED AT 250 WORDS)

Antagonism of antihypertensive drug therapy by nonsteroidal anti-inflammatory drugs

Certain nonsteroidal anti-inflammatory drugs antagonize the action of antihypertensive therapy. Indomethacin has been shown to abrogate the antihypertensive effect of beta-adrenergic receptor blockers, diuretics, converting enzyme inhibitors, and several antihypertensive drug combinations, and the accumulated evidence on piroxicam indicates that it also raises arterial pressure in treated patients. In contrast, sulindac and aspirin do not reverse the effects of antihypertensive drugs, and currently available data indicate that they are the safest cyclooxygenase inhibitors for use in hypertensive patients. In the absence of definitive information on the array of other nonsteroidal anti-inflammatory drugs, they should be considered to pose a risk similar to indomethacin until proved otherwise. The magnitude of the elevation in blood pressure varies between patients, ranging from no effect to dangerous hypertensive responses. Generalized inhibition of the cyclooxygenase enzyme has opposing effects on arterial pressure, lowering renin on one hand and causing sodium retention on the other. Some evidence suggests that cyclooxygenase inhibition causes the greater increments in pressure in patients who initially have low plasma renin activity (often the elderly). The potential for cerebral vascular catastrophes attends these drug interactions in which platelet function also is suppressed by cyclooxygenase inhibition.

Captopril before and after spironolactone therapy in primary aldosteronism. Pathogenetic and therapeutical aspects

In three patients with primary aldosteronism, the acute effect of a single dose of captopril on the elevated mean arterial blood pressure (MAP) was studied before and after 4 weeks of treatment with spironolactone. Before spironolactone therapy, captopril did not cause any drop in MAP. Four weeks later, after an oral daily dose of 400 mg spironolactone, MAP was still elevated in all three patients, though electrolyte abnormalities were fully corrected. Since plasma renin activity (PRA) was increased to values above the normal range, the acute effect of captopril on MAP was tested again. A single dose of 25 mg captopril then caused a fall in MAP to normal. These data reveal the conversion from a renin-independent to a renin-dependent kind of hypertension after spironolactone therapy in three patients with primary aldosteronism syndrome. This might be of pathogenetic and therapeutic interest.

The role of prostaglandins in human hypertension

A large body of evidence supports the concept that prostaglandins (PG) are importantly involved in arterial pressure regulation. Various PGs, especially PGE2 and prostacyclin (PGI2) may influence blood pressure through control of vascular tone, sodium excretion, and renin release. Inhibition of PG synthesis by nonsteroidal antiinflammatory drugs (NSAID) augments the vasoconstrictor response to exogenous pressors such as angiotensin II, arginine vasopressin (AVP), and fludrocortisone. The acute administration of NSAID to either normotensive or untreated hypertensive subjects results in an increase in arterial pressure and peripheral resistance; long-term administration, however, is associated with little or no change in blood pressure, possibly because of a reduction in cardiac output. Although NSAID have little influence on blood pressure in normotensive subjects or untreated hypertensives, inhibition of PG synthesis blunts or abolishes the antihypertensive effect of most antihypertensive agents. NSAID antagonize the vasodepressor action of diuretics, beta-adrenoreceptor antagonists, vasodilators, and converting enzyme inhibitors. Consequently, potent NSAID should be used with caution, if at all, during treatment of hypertensive patients. Numerous studies have examined renal PG production in essential hypertension (EH). The majority have demonstrated reduced basal and stimulated urinary PGE2 excretion in EH compared to normotensive subjects, but there is substantial overlap. Nevertheless, renal PGE2 synthesis is significantly decreased in approximately one-third of patients with EH. A recent innovative approach to arterial pressure regulation has focused on dietary supplementation with polyunsaturated fatty acids (PUFA), especially linoleic acid and eicosapentaenoic acid. Several groups have demonstrated that long-term dietary supplementation with PUFA reduces blood pressure in both normotensive individuals and in patients with EH.(ABSTRACT TRUNCATED AT 250 WORDS)

[Renal failure caused by non-steroid anti-inflammatory agents]

This review of literature about non steroidal anti-inflammatory drugs renal accidents is an analysis of acute pathology and a study of renal dysfunctions induced by these drugs. Each chapter allows a physiopathologic study. The care of anti-inflammatory drugs utilisation is specified.

Differential blood pressure and metabolic effects of 9 alpha-fluorocortisol in man

The blood pressure and metabolic effects of 9 alpha-fluorocortisol at 0.15 mg/day and 1.5 mg/day were examined in man. At high dose, systolic pressure and body weight rose, and plasma [K+], urinary sodium excretion and renin concentration fell. At low dose similar metabolic effects were seen but blood pressure was unchanged. 9 alpha-Fluorocortisol has 'mineralocorticoid' effects in man at a dose which does not alter blood pressure. These studies do not provide evidence of a 'hypertensinogenic' class of steroid hormone action in man.

Evidence for a dual action of converting enzyme inhibitor on blood pressure in normal man

We studied the effect of a converting enzyme inhibitor (CEI), Captopril SQ 14,225 50 mg p.o. in eight supine normal subjects under a high sodium (150 mEq/d) and low sodium (25 mEq/d) diet. On high sodium, plasma renin (PRA) and aldosterone were basal and Saralasin did not lower mean blood pressure. However, CEI induced an 11.4 +/- 3.2 mm fall in blood pressure (p less than 0.02) and either indomethacin 50 mg or ibuprofen 800 mg (PI), when given simultaneously on another day abolished the blood pressure response (2.5 +/- 0.9 mm Hg, p greater than 0.5). In contrast, on a low salt diet where renin was increased, CEI induced a drop in blood pressure which was not significantly altered by PI (12.8 +/- 1.1 vs. 10.0 +/- 3.1 mm Hg, p greater than 0.5). CEI increased plasma renin on both diets (1.7 +/- 0.5 to 3.5 +/- 0.8 and 2.8 +/- 0.6 to 12.5 +/- 3.1 ng/ml/hr respectively both p less than 0.05). Aldosterone did not change (high Na+) or fell (low Na+). Inhibition of Prostaglandin synthesis did not significantly block the renin rise from CEI suggesting that the direct angiotensin II negative feedback is relatively independent of acute prostaglandin release. Our studies suggest that CEI has a dual hypotensive action. In a low renin state, the hypotensive action appears to be mediated through vascular prostaglandins.