Effects of ET-1 on water and chloride transport in cortical collecting ducts of the rat.

Endothelin-1 (ET-1) is known as a vasoconstrictor peptide. However, recent reports suggested the effects on the transport of renal tubule. We previously reported that ET-1 inhibited arginine vasopressin (AVP)-dependent adenosine 3',5'-cyclic monophosphate in rat collecting ducts. Physiologically, ET-1 reversibly and significantly inhibited AVP-stimulated water permeability in inner medullary collecting duct (IMCD). We therefore investigated the effects on water and electrolyte transport in rat cortical collecting ducts (CCD), where Na and Cl are actively reabsorbed more than in IMCD. Pathogen-free male Sprague-Dawley rats weighing 80-120 g were used after treatment with deoxycorticosterone pivalate for 1-2 wk. Isolated CCD were microperfused in vitro. The Cl concentration was measured by a continuous-flow ultra-microcolorimeter, and the raffinose concentration was measured as a volume marker by a continuous-flow ultra-microfluorometer. In the presence of 10(-9) M AVP, 10(-8) M ET-1 significantly inhibited fluid absorption (nl.mm-1 x min-1) from 0.25 +/- 0.02 to 0.15 +/- 0.05 (mean +/- SE, n = 6, P < 0.01), Cl absorption (pmol.mm-1 x min-1) from 30. 6 +/- 2.8 to 14.9 +/- 4.0 (P < 0.01), and potential difference (mV) from -5.4 +/- 1.3 to -4.0 +/- 1.2 (P < 0.01). Similar results were obtained in the lower concentration of 10(-10) M AVP and 10(-10) M ET-1. As for the osmotic water permeability (microns/s), 10(-8) M ET-1 significantly inhibited this from 320.1 +/- 50.9 to 202.1 +/- 42.2 (n = 7, P < 0.01) in the presence of 10(-9) M AVP.(ABSTRACT TRUNCATED AT 250 WORDS)