Suppressed renin release during hyperoxia in the conscious dog

Recent studies have documented a marked inhibition of renal prostaglandin E₂ excretion during hyperbaric oxygenation (HBO) in the conscious dog. Numerous other studies have shown that pharmacological inhibition of prostaglandin synthesis is associated with diminished renin release. The current experiments were designed to test whether HBO is also accompanied by reduced renin secretory rate (RSR) in conscious dogs. Dogs were implanted with electromagnetic flow probes on the left renal artery as well as with chronic arterial and renal venous catheters. Renal blood flow, peripheral plasma renin activity, and renal venous renin activity were measured, which allowed calculation of RSR for the left kidney. The dogs were studied at normal atmospheric pressure while breathing room air, followed by exposure to 100% oxygen at 2 or 3 ATA. The dogs were then returned to room air. The RSR decreased from 153.6±51.6 (ng.h^-1)xmin^-1 to 72±21 ng.h^-1)xmin^-1 during HBO. Upon return to normoxia, RSR rose to 345±140.4 ng.h^-1)xmin^-1. This renin response to HBO seems best related to the previously documented inhibition of renal prostaglandin synthesis. These experiments provide nonpharmacological evidence that there may be a functional relationship between the renin-angiotensin system and renal prostaglandin release in awake animals.