RAT RENAL INTERSTITIAL BRADYKININ, PROSTAGLANDIN E(2), AND CYCLIC GUANOSINE 3',5'-MONOPHOSPHATE - EFFECTS OF ALTERED SODIUM-INTAKE

Kinins generated intrarenally probably affect renal function by alteri ng levels of various mediators and messengers, including prostaglandin E(2) (PGE(2)) and cyclic guanosine 3',5'-monophosphate (cGMP). Using a microdialysis technique, we monitored levels of cortical and medulla ry renal interstitial fluid kinins, PGE(2), and cGMP after 5 days of 0 .15% (low), 0.28% (normal), or 4.0% (high) sodium intake. Samples were collected from anesthetized rats (n = 5 for each diet). During normal sodium intake, renal interstitial fluid kinin, PGE(2), and cGMP level s in dialysate leaving the cortex were 113+/-8 pg/min, 1.23+/-0.11 pg/ min, and 0.05+/-0.004 pmol/min, respectively. In the fluid leaving the medulla, the levels were 93.0+/-17 pg/min, 2.28+/-0.14 pg/min, and 0. 08+/-0.005 pmol/min, respectively. In rats consuming a low sodium diet , renal cortical interstitial fluid kinin and cortical and medullary P GE2( )and cGMP appearance rates were significantly increased (P<.01). Rats consuming a high sodium diet showed renal cortical and medullary kinin levels that were decreased 100-fold (P<.01), whereas PGE(2) and cGMP were increased (P<.01) compared with levels in rats with normal s odium intake. Renal interstitial fluid kinin is extremely sensitive to dietary sodium, but changes in interstitial fluid PGE(2) and cGMP are not always directionally similar, suggesting different regulations of these substances in response to sodium intake.