Kinin and tubuloglomerular feedback in normal and hydronephrotic rats.

The role of bradykinin in resetting the tubuloglomerular feedback (TGF) mechanism was studied with the stop-flow technique in control and hydronephrotic Inactin-anesthetized rats. Glomerular function was assessed by measuring stop-flow pressure (Psf); the maximal decrease in stop-flow pressure (delta Psf) with increased loop of Henle perfusion and the perfusion that elicited half-maximal delta Psf, the turning point (TP), were determined. Bradykinin infusion resulted in resetting of TGF in both control and hydronephrotic rats but in different directions. A decreased sensitivity was found in control rats (TP increased from 18.6 to 26.4 and 16.8 to 22.1 nl/min on systemic and intratubular administration, respectively). In hydronephrotic rats the sensitivity of TGF increased. TP decreased from 19.9 to 15.2 nl/min with bradykinin administered systemically and from 18.4 to 15.0 nl/min on intratubular administration. These results show that exogenous kinin administration mimics the effects of extracellular volume expansion on TGF resetting and demonstrate a difference in resetting in hydronephrotic and control kidneys.