Increase of plasma renin activity in male and female rabbits subjected to dysbaric conditions

The renin-angiotensin-aldosterone system may be implicated in hemodynamic alterations occurring in dysbaric disorders. This report concerns changes in plasma renin activity (PRA) induced by exposure of rabbits to a compression-decompression schedule that does not normally produce clinical manifestations of decompression sickness (DS). The results revealed a significant increase in PRA in 19 of 23 animals following dysbaric exposure. Mean PRA rose from 1.18 ng Angl · ml^-1 · hr^-1 (preexposure) to 2.40 ng Angl · ml^-1 · hr^-1 (postexposure). The increase was particularly pronounced in female animals (217%). Asymptomatic intravascular gas bubbles ('silent bubbles') were detected by gross or microscopic examination in the majority of the animals. Renin elaboration and secretion in asymptomatic dysbaric exposures may be mediated by bradykinin and/or prostaglandins released or activated in a chain reaction triggered by silent gas bubbles. This hypothesis is also applicable to increased PRA in altitude decompression. Alternatively elevation of PRA may result from decreased renal perfusion when dysbaric disorders are complicated by significant hypovolemia.