Acute postural changes in aldosterone and electrolyte excretion in man

Abstract

The renal responses to change of posture have been ascribed to changes in renal haemodynamics (Rosenbaum, Ferguson, Davis & Rossmeisl, 1952); but Thomas (1957) has produced evidence that, at least in prolonged experiments, there is a change of tubular function such as could be produced by an increased secretion of aldosterone. There is evidence (Muller, Manning & Riondel, 1958) that aldosterone output over periods of twelve hours is higher in ambulant subjects than in those who remain in bed. Changes in output in relation to posture have not, however, been demonstrated over shorter periods such as those here reported. It has often been suggested that secretion of aldosterone is regulated by 'volume receptors' at some unknown situation (e.g. Bartter, Liddle, Duncan, Barber & Delea, 1956); if posture can be shown to affect aldosterone output, it seems likely that the same volume receptor mechanism is involved, and postural studies may therefore contribute towards the location of these receptors.A preliminary account of this work has already appeared (Gowenlock, Mills & Thomas, 1958). METHODSObservations were made on healthy male subjects, 25 medical students and one of the authors (J.N.M.). For each experiment groups of 3-8 subjects were used; in order to investigate changes of aldosterone excretion over short periods, urine from the group of subjects was pooled, as only thus was it possible to obtain the 8-12 man-hours of urine required for accurate assay by the method used. Except in experiments 7 and 8 no two groups had the same composition; each subject was used in one to four experiments.After a light breakfast without tea or coffee, subjects voided and discarded their urine at about 10.30 and then lay down for 2 or 24 hr before voiding sample 1. They then either remained recumbent, for 5 hr in all, voiding sample 2 at the end; or they changed their posture to standing or sitting, voiding and discarding the urine after 1 hr and collecting the urine passed in the followng 2 hr; or they remained recumbent and received an intravenous injection of 0-25 mg DL-aldosterone-21-monoacetate (Ciba), in 95% ethanol, diluted with isotonic NaCl, repeated 1j hr later, and collected the urine passed during 3 hr from the first injection. They drank when thirsty. Small samples of urine from each subject were removed for separate analysis of Na and K * Present address: Department of Pathology, University of Manchester.

A diurnal rhythm in plasma renin activity in man.

“…can prevent the posturally induced fall in sodium o partially pre-excretion (19) and the posturally induced rise in n plasma renin aldosterone excretion (13). It seems reasonable en subjects who to assume that it was through the prevention of a fall in renal blood flow that bandaging the ex-UBJECTS tremities prevented a posturally induced rise in 2 UPRIGHT plasma renin activity of the subjects in the present study.…”

“…Aldosterone production decreases in the afternoon because the diurnal rhythm mechanism tends to negate the influence of upright posture on renin production during that portion of the day. Although the large increases in plasma renin activity that occur after assumption of upright posture have been shown to be accompanied by increases in aldosterone excretion (12)(13)(14), further studies will be necessary to establish whether the more modest variations in plasma renin activity in recumbent subjects described in this study are accompanied by parallel variations in aldosterone excretion.…”

“…It has been shown previously that upright posture is associated with a reases in plasma fall in renal blood flow (17), a decrease in urinary i those observed sodium (18), and a rise in urinary aldosterone 6). Control of (12)(13)(14). By bandaging the lower extremities t change did not before the patient assumes upright posture, one l activity.…”

“…Before it was known that angiotensin had a role in the regulation of aldosterone secretion, a large number of studies indicated that experimental or pathological conditions that resulted in a reduction of effective blood volume would stimulate aldosterone secretion (7). Studies have already been published indicating that plasma renin activity and aldosterone excretion both increase in response to sodium deprivation (8)(9)(10) and assumption of upright posture (11)(12)(13).…”

Proceedings of the Physiological Society, 28 September 1962, Cambridge Meeting: Communications

“…The diurnal variation in sweat Na: K observed in the present experiments may correspond to more rapid changes in renal electrolyte excretion which have been partly attributed to the effects of posture on endogenous aldosterone activity (Gowenlock, Mills & Thomas, 1959 …”