RENAL INTERSTITIAL FLUID ANGIOTENSIN - MODULATION BY ANESTHESIA, EPINEPHRINE, SODIUM DEPLETION, AND RENIN INHIBITION

Using a microdialysis technique, we monitored changes in right and lef t renal interstitial fluid angiotensins in anesthetized and conscious dogs (both n=5) in response to right renal interstitial epinephrine (0 .2 mg/kg per minute) administration. Renal interstitial and plasma ang iotensin levels also were monitored in conscious dogs (n=4) in respons e to dietary sodium deprivation (10 mmol/d) for 5 consecutive days. Ch anges in renal interstitial and plasma angiotensins in response to int erstitial administration of a specific renin inhibitor, ACRIP (0.5 mu g/kg per minute for 20 minutes), were monitored on day 5 of sodium dep letion. At basal levels, there were no significant differences between the right and left renal interstitial immunoreactive angiotensin leve ls in anesthetized dogs. Renal interstitial epinephrine administration caused a significant increase in renal interstitial immunoreactive an giotensin concentrations in both anesthetized and conscious dogs (P<.0 1). However, anesthetized dogs had significantly higher renal intersti tial immunoreactive angiotensin levels basally and in response to epin ephrine than conscious dogs (P<.05). Renal interstitial immunoreactive angiotensin concentrations increased significantly and progressively during exposure to a low sodium diet from 3.9+/-1 nmol on day 1 to 740 +/-332 nmol on day 5 (P<.01). Renal interstitial immunoreactive angiot ensin decreased significantly to 124+/-37 nmol (P<.01) in response to intrarenal renin inhibition at the end of day 5 of sodium depletion. P lasma immunoreactive angiotensin increased significantly (P<.01) in re sponse to sodium depletion, and no change occurred during intrarenal r enin inhibition. We conclude that anesthesia, epinephrine, sodium depl etion, and renin inhibition modulate renal interstitial angiotensin, w hich may serve as an important physiological regulator.