Journal of applied physiology: respiratory, environmental and exercise physiology vol:45 issue:3 pages:403-7
Mean intra-arterial pressure (P-), heart rate (HR), cardiac index (CI), total peripheral resistance index (TPRI), and plasma renin activity (PRA), norepinephrine (PNE), and epinephrine (PE) were estimated in five normal male subjects placed on a low-sodium diet for the previous 7 days. Subjects were studied during rest in recumbency and during intravenous infusion of either glucose or saralasin in a) recumbent position, b) sitting position on the bicycle ergometer, and c) during submaximal graded exercise. At rest recumbent saralasin induced pressure changes that were closely related to logPRA. During exercise the increase in P- was significantly lower during saralasin as compared to glucose from 110 W on, related to a greater reduction in TPRI. The increase of PRA during exercise was about three times greater with saralasin as compared to glucose, but the rises in PNE and PE were similar in both series of tests. Angiotensin II may thus have a role in the maintenance of P- in the supine sodium-deplete normal subjects, and stimulation of the renin angiotensin system during physical exercise contributes to a minor extent to the increase in P- in these conditions.