Rat renal interstitial bradykinin, prostaglandin E2, and cyclic guanosine 3',5'-monophosphate : effects of altered sodium intake

Kinins generated intrarenally probably affect renal function by altering levels of various mediators and messengers, including prostaglandin E2 (PGE2) and cyclic guanosine 3',5'-monophosphate (cGMP). Using a microdialysis technique, we monitored levels of cortical and medullary renal interstitial fluid kinins, PGE2, 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, PGE2, and cGMP levels 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 PGE2 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 PGE2 and cGMP were increased (P < .01) compared with levels in rats with normal sodium intake. Renal interstitial fluid kinin is extremely sensitive to dietary sodium, but changes in interstitial fluid PGE2 and cGMP are not always directionally similar, suggesting different regulations of these substances in response to sodium intake.