Effects of hydration state on hormonal and renal responses during moderate exercise in the heat

Abstract

The effects of hydromineral hormones and catecholamines on renal concentrating ability at different hydration states were examined in five male volunteers while they performed three trials. Each of these trials comprised a 60-min exercise bout on a treadmill (at 50% of maximal oxygen uptake) in a warm environment (dry bulb temperature, 35 degrees C; relative humidity, 20-30%). In one session, subjects were euhydrated before exercise (C). In the two other sessions, after thermal dehydration (loss of 3% body mass) which markedly reduced plasma volume (PV) and increased plasma osmolality (osm[pl]), the subjects exercised either not rehydrated (Dh) or rehydrated (Rh) by drinking 600 ml of mineral water before and 40 min after the onset of exercise. During exercise in the Dh compared to C state, plasma renin, aldosterone, arginine vasopressin (AVP), noradrenaline and adrenaline concentrations were increased (P < 0.05). A reduction in creatinine clearance and urine flow was also observed (P < 0.05) together with a decrease in urine osmolality, osmolar clearance and sodium excretion, while free water clearance increased (P < 0.05). However, compared to Dh, Rh partially restored PV and osm(pl) and induced a marked reduction in the time courses of both the plasma AVP and catecholamine responses (P < 0.05). Values for renal water and electrolyte excretion were intermediate between those of Dh and C. Plasma atrial natriuretic peptide presented similar changes whatever the hydration state. These results demonstrate that during moderate exercise in the heat, renal concentrating ability is paradoxically reduced by prior dehydration in spite of high plasma AVP levels, and might be the result of marked activation of the sympatho-adrenal system. Rehydration, by reducing this activation, could partially restore the renal concentrating ability despite the lowered plasma AVP.

Thermoregulation in hypertensive men exercising in the heat with water ingestion

“…The similar P osm , V u , G u , sweat rate, and dehydration level results for hypertensive and normotensive indicate a physiological response of both groups and a partial replacement of fluid losses with water ingestion, as expected (22,23).…”

Effect of hydration on exercise-induced growth hormone response

“…In order to preservē uid homeostasis, arginine vasopressin and aldosterone secretion are stimulated (18). However, when exercise is performed with¯uid replacement, secretion of arginine vasopressin and aldosterone is inhibited (19,20).…”

The Fathers of Italian Histology

“…The expression of receptors for these hormones in developing and adult muscle and in satellite adds to the physiological relevance of these data. It is particularly interesting that several reports indicate that muscular exercise results in a significant increase of circulating AVP, both in human and in other mammals, thus posing the theoretical basis for the physiological regulation of muscle hypertrophy by neurohypophyseal hormones (Melin et al, 1980;Convertino et al, 1981;Alexander et al, 1991;Melin et al, 1997). Furthermore the calcineurin pathway, which is strongly stimulated by AVP, was shown to be essential for muscle regeneration in normal and dystrophic animals (Stupka et al, 2004); and determination of muscle specificity, an important factor in muscle development, is finely regulated by SM22, which in turn is regulated by AVP (Chang et al, 2001;Kaplan-Albuquerque et al, 2003).…”