EFFECTS OF ENDOTHELIN-1 ON PHOSPHATE-TRANSPORT IN BRUSH-BORDER MEMBRANE-VESICLES

Endothelin is the most potent vasoconstrictive agent released from end othelial and many other types of cells. It has been reported that endo thelin has physiological effects on the rat kidney, especially on the renal proximal tubules. We investigated the role of endothelin 1 in th e renal brush border membrane. The V-max of P-i uptake by brush border membrane vesicles (BBMV) in the endothelin-1-treated group was signif icantly greater than that in the control group. There were no signific ant changes in apparent K-m values between the two groups. To define t he direct effect of endothelin I on P-i transport of BBMV, BBMV from n ormal rats were incubated with endothelin 1 in vitro. The P-i uptake b y BBMV incubated with endothelin 1 did not differ from that by BBMV in cubated with a salt solution as a control. These results suggested the probability of the presence of endothelin 1 receptor in the proximal tubules. Administration of the endothelin 1 might increase the P-i rea bsorption by BBMV according to changes in the capacity of the transpor ter.