Effects of Low Salt Plus Upright Posture, Angiotensin II, ACTH, and Potassium upon Plasma Renin Activity, Aldosterone, and Cortisol
1
Citation
0
Reference
10
Related Paper
Abstract:
In order to study the control system of plasma aldosterone in human, we examined the effects of low salt plus upright posture, angiotensin II, ACTH and potassium upon plasma renin activity, aldosterone and cortisol in five subjects who were supposed to be normal. All of the procedures, low salt diet with below 3 g of salt and 2 hr-upright posture, 0.25 mg of Cortrosyn, angiotensin infusion to increase 20 mmHg of diastolic pressure for an hour, and 30 mEq of potassium infusion stimulated plasma aldosterone significantly. Furthermore, in each subject the degrees of response to each of these stimulations were almost same.In an old woman aged 68, responses to all of stimulations were significantly lower than those in other subjects.Plasma cortisol was significantly stimulated by ACTH, but slightly reduced by potassium infusion. From these results, it is certain that plasma aldosteron levels are easily affected by a small amount of changes in angiotensin, ACTH, potassium and sodium. However, responses of aldosterone to these changes seem to be decreased in old subjects.Keywords:
Plasma renin activity
The influence of adrenalectomy and administration of aldosterone on potassium secretion by colonic epithelium was studied in vivo in rats, particularly in relation to potassium adaptation (induced by feeding a potassium-rich diet) and the response to acute i.v. administration of a potassium load. Adrenalectomy (rats maintained on dexamethasone and saline) impaired the development of potassium adaptation or considerably reduced it if the rats had been previously adapted. The partial adaptation observed in the adrenalectomized rats may be related to the increased plasma potassium concentration developed when these rats received the potassium-rich diet. Within 2 h of acute aldosterone administration, the response of the potassium secretion rate to acute potassium loading in adrenalectomized rats was significantly improved. When aldosterone (2 micrograms/day per 100 g body weight, given by osmotic minipump) was added to the replacement treatment, the plasma concentration of potassium was similar to that of the intact rats, and both potassium adaptation and the response to the acute potassium load were completely restored. Transepithelial potential difference and sodium transport were not stimulated, being similar to the values in intact rats. Considerable changes in potassium secretion induced by acute potassium loading did not significantly affect sodium transport. The findings suggest that the sodium and potassium epithelial pathways are, to a large extent, independently influenced by aldosterone. Aldosterone appears to be essential for complete adaptation and, in a relatively low dose, can completely restore potassium adaptation and the response to acute potassium loads in adrenalectomized rats.
Cite
Citations (4)
bjective To investigate changes of plasma
renin activity (PRA) and aldosterone (ALD) level during 21 d -6headdown bedrest (HDT) with and
without cuffs. Methods The -6 head down bedrest 21 d was used to simulate weightlessness.
Twelve volunteers were divided into 2 groups, control group and cuffs group. In cuffs group,
cuffs on the upper parts of thighs and arms were inflated 12 h/d during 110 d,1821 d of bedrest.
No countermeasures were used in control group. Samples of plasma were taken before and
during HDT. Plasma renin activity and aldosterone were measured by radioimmunoassay.
Results PRA levels were elevated and the peak values revealed at D4, D10 respectively in
control and cuffs groups, and then declined to the preHDT level by the end of 21 d HDT in both
groups. In control group, plasma aldosterone level decreased at D2, and then increased at D4,
D10, D21.No significant difference was observed between two groups. Conclusions HDT
induces the initial hormonal response with a decrease in plasma aldosterone. The long term
effects of HDT are linked to increase of plasma renin activity and aldosterone. The change of
plasma aldosterone can be alleviated by using cuffs during HDT.
Plasma renin activity
Plasma levels
Cite
Citations (0)
Potassium deficiency
Mineralocorticoid
Cite
Citations (52)
Components of the renin-angiotensin system (plasma renin activity, total and inactive renin, angiotensinogen and angiotensin II) were examined in 90 patients with labile and stable essential hypertension before and after functional and pharmacologic tests. New data have been obtained on intrasystemic regulatory mechanisms of the pressor renin-angiotensin systems. Different patterns of plasma active and inactive renin variations in response to salt loading are demonstrated in patients with different "renin" variants of essential hypertension. Angiotensin II is shown to have a stimulating effect on angiotensinogen synthesis.
Plasma renin activity
Essential hypertension
Cite
Citations (0)
Plasma renin activity
Essential hypertension
Hyperaldosteronism
Cite
Citations (53)
The enzyme renin ( M r ∼40 000) is released in an active form from the renal juxtaglomerular cells in response to physiologic factors, including sodium depletion, decreased blood volume and blood pressure, and β-adrenergic stimulation (1). Although several local angiotensin II-generating systems exist within various tissues (including the heart, brain, and adrenal glands), the concentration of active renin in plasma depends on the rate of renin secretion from the kidneys (2). Renin catalyzes the formation of angiotensin I (AngI) by cleavage of the renin substrate called angiotensinogen. Plasma renin is therefore the initiator of the renin-angiotensin-aldosterone system, which has an important role in the homeostasis of water and electrolyte balance and in the regulation of arterial pressure.
In most studies, circulating renin has been estimated by assays of plasma renin activity (PRA). PRA is measured by generating AngI from endogenous angiotensinogen, followed by measurement by RIA of the generated AngI. Although PRA measurement is convenient for estimating the biological activity of the renin system, it may not necessarily reflect the real concentration of active renin. The concentration of substrate rarely affects the PRA result, but exceptions do occur (3). More importantly, PRA depends not only on renin, but also on factors that influence the renin–renin substrate interaction.
An additional difficulty occurs in measuring low concentrations of renin. In the PRA method, prolonged incubation is needed to generate measurable AngI. This is specifically important when measuring PRA in black people because their values are often below the limit of detection of the routine PRA method. This complicates and prolongs the method and makes it impractical for large throughput for population-based studies.
Immunoassays are available to quantify renin directly with use of monoclonal antibodies. In addition, interlaboratory CVs are lower with immunoassays than with PRA assays (4).
A new method for …
Plasma renin activity
Homeostasis
Juxtaglomerular apparatus
Cite
Citations (59)
Plasma renin activity
Mineralocorticoid
Essential hypertension
Cite
Citations (8)
We studied 52 patients with mild to severe essential arterial hypertension and ranging in age from 30 to 60 years (average, 44). Various biochemical and endocrinologic parameters were studied, with special emphasis on plasma aldosterone and urinary aldosterone. At the same time, a control group of 30 normal subjects (nonhypertensive) were studied under the same conditions. Both groups were carefully selected. Results indicated that the hypertensive group demonstrated a marked increase in plasma aldosterone levels (P less than .01) and an increase in the coefficient of plasma aldosterone/plasma renin activity (P less than .01). This indicates inadequate secretion of plasma aldosterone. There were no significant changes in the urinary aldosterone. Statistically significant changes were found in plasma renin activity (P less than .001) and plasma aldosterone (P less than .001) when the hypertensive patients were divided into two age groups, those under 45 and those over 45. These changes were not found in the normal subjects in the same age groups, indicating that age is an important influence on the renin-aldosterone system in hypertensive patients, and leads to variations in this hormonal axis similar to those observed in normal elderly subjects.
Plasma renin activity
Essential hypertension
Plasma levels
Cite
Citations (4)
AbstractHomogenates of rat aortic wall can generate angiotensin I when incubated with nephrectomised rat plasma. This renin-like activity is due to a mixture of proteolytic enzymes. Thus the capacity to generate angiotensin I is greater at pH 5.3 than pH 6.5, although the latter is the pH optimum for rat renal renin. The present work addresses itself to two questions. Is this activity derived from plasma renin? Secondly, does vascular renin-like activity play a role in blood pressure control? Plasma and aortic renin were altered by bilateral nephrectomy and modulation of salt intake. In addition four models of hypertension were studied (early and chronic Goldblatt 2-kidney 1-clip, DOC-salt and spontaneous hypertension). The results indicated that in steady state conditions, aortic and plasma renin-like activity (measured with an incubation pH of 6.5) changed in parallel. When plasma renin was altered acutely however by intravenous injection of renin into nephrectomised rats the half-life of plasma renin was much shorter than the half life of aortic renin. Under these circumstances the pressor response to renin correlated much better with aortic than with plasma renin-like activity. Whilst these studies suggest therefore that renin taken up by the arterial wall is an important determinant of blood pressure, they provide no evidence that accumulation of renin locally produces hypertension in the presence of normal or low plasma renin activity.Key Words: arterial reninrenin-like activityblood pressureGoldblatt hypertensionspontaneously hypertensive ratsdeoxycorticosterone-salt hypertension
Plasma renin activity
Cite
Citations (12)
Plasma renin activity
Saralasin
Cite
Citations (30)