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Updated: Jul 14, 2026

Single-channel Analysis and Calcium Imaging in the Podocytes of the Freshly Isolated Glomeruli
Published on: June 27, 2015
Endothelin's biphasic effect on fluid absorption in the proximal straight tubule and its inhibitory cascade
1Division of Hypertension and Vascular Research, Henry Ford Hospital, Detroit, Michigan 48202.
Abstract:
The effect of endothelin-1 (ET-1) on the proximal tubule remains unclear. This may be due to a biphasic effect on transport in this segment. We hypothesized that ET-1 has a biphasic effect on fluid absorption (Jv) in the proximal straight tubule and that its inhibitory effect is superimposed on its stimulatory effect. ET-1 (10(-13) M) stimulated Jv from 0.68 +/- 0.07 to 1.11 +/- 0.20 nl/mm/min, a 60% increase (P < 0.04). 10(-12) and 10(-10) M ET-1 had no significant effect. 10(-9) M ET-1 reduced Jv from 0.81 +/- 0.19 to 0.44 +/- 0.15 nl/mm/min (P < 0.009). Staurosporine (STP, 10(-8) M) prevented both 10(-9) and 10(-13) M ET-1 from altering Jv significantly indicating that protein kinase C (PKC) is involved. Indomethacin (10(-5) M) blocked the inhibition produced by 10(-9) M ET-1. ETI (10(-6) M), a lipoxygenase inhibitor, also blocked ET-1 inhibition of Jv. Interestingly ET-1 (10(-9) M) stimulated Jv in the presence of both indomethacin and ETI. When 10(-9) M ET-1 was added in the presence of 10(-5) M quinacrine, a phospholipase (PL) inhibitor, Jv also increased from 1.02 +/- 0.20 to 1.23 +/- 0.22 nl/mm/min (P < 0.03). STP blocked this increase. We conclude that (a) 10(-13) M ET-1 stimulates fluid absorption by activating PKC; (b) 10(-9) M ET-1 decreases Jv by PKC-, PL-, cyclooxygenase-, and lipoxygenase-dependent mechanisms; and (c) the inhibitory effect of ET-1 on Jv is superimposed on the stimulatory effect.
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