The effect of orthostatism, passive tilting and recumbent exercise on renin release.

Three postural tests, orthostatism, passive tilting and recumbent exercise, were applied to fourteen normal volunteers. Orthostatism and tilting produce a significant increase in plasma renin activity (PRA) and plasma renin concentration (PRC), without changes in plasma renin substrate concentration (PSC). Recumbent exercise induces an inhibition of PRA and PRC and does not changes PSC. The present study seems to suggest that sympathetic activity and intravascular blood volume could play an important role in the responses of the renin-angiotensin system to postural changes.