ANG II controls Na(+)-K+(NH4+)-2Cl- cotransport via 20-HETE and PKC in medullary thick ascending limb

Abstract

Cell pH was monitored in medullary thick ascending limbs to determine effects of ANG II on Na(+)-K+(NH4+)-2Cl- cotransport. ANG II at 10(-16) to 10(-12) M inhibited 30-50% (P < 0.005), but higher ANG II concentrations were stimulatory compared with the 10(-12) M ANG II level cotransport activity; eventually, 10(-6) M ANG II stimulated 34% cotransport activity (P < 0.003). Inhibition by 10(-12) M ANG II was abolished by phospholipase C (PLC), diacylglycerol lipase, or cytochrome P-450-dependent monooxygenase blockade; 10(-12) M ANG II had no effect additive to inhibition by 20-hydroxyeicosatetranoic acid (20-HETE). Stimulation by 10(-6) M ANG II was abolished by PLC and protein kinase C (PKC) blockade and was partially suppressed when the rise in cytosolic Ca2+ was prevented. All ANG II effects were abolished by DUP-753 (losartan) but not by PD-123319. Thus < or = 10(-12) M ANG II inhibits via 20-HETE, whereas > or = 5 x 10(-11) M ANG II stimulates via PKC Na(+)-K+(NH4+)-2Cl- cotransport; all ANG II effects involve AT1 receptors and PLC activation.