PROTEIN-KINASE-C ISOFORMS IN RAT-KIDNEY PROXIMAL TUBULE - ACUTE EFFECT OF ANGIOTENSIN-II

The present study examined the effect of phorbol esters, Ca2+, and ang iotensin II (ANG II) on protein kinase C (PKC) isoforms in the rat pro ximal tubule. The immunoblot analysis of PKC isoforms of particulate a nd cytosolic fractions of proximal tubules revealed immunoreactive pro teins when antibodies against PKC-alpha -delta -epsilon and -zeta, but not -beta and -gamma were used. Phorbol dibutyrate (PDBU) induced the translocation of PKC-alpha, -delta, and -epsilon, whereas an inactive phorbol ester had no effect. PDBU and ionomycin increased particulate PKC specific activity from 0.67 +/- 0.09 to 1.56 +/- 0.18 and 0.96 +/ - 0.04 pmol .mu g protein(-1). 2 min(-1), respectively. ANG II (10(-7) M) induced a time-dependent increase in particulate PKC-alpha immunor eactivity observed after 2 min and maintained for 12 min. Particulate PKC-epsilon immunoreactivity increased after 4 min. Meanwhile, PKC-del ta and -zeta were not modified by ANG II. Accordingly, ANG II elicited a rise in the specific activity of the particulate PKC, which increas ed to 0.89 +/- 0.09 pmol .mu g protein(-1). 2 min(-1) after 2 min. Thi s was inhibited by a preincubation in the presence of 10(-5) M losarta n, specific inhibitor of angiotensin subtype 1 receptors. These data i ndicate that PKC-alpha and -epsilon are potential candidates to regula te the activity of Na+/H+ and Na+-HCO3- transporters because they are translocated with a time course fitting with that of the reported effe ct of ANG II on those transporters.