K+ loading, but not Na+ loading, and blockade of ATP-sensitive K+ channelsaugment renal kallikrein secretion

This study aimed to examine whether K+ loading or Na+ loading augments rena l kallikrein (KK) secretion. It also investigated the effect of blockade of renal ATP-sensitive K+ channels on renal KK secretion. Rats were administe red 50 mmol/kg body weight of KCl. Twelve-hour collected urine was measured for urinary excretion of K+ and Na+ and urinary activity of renal KK. Incr eases in urinary excretion of K+ and Na+ by K+ loading accompanied an incre ase in renal KK secretion. In another experiment, rats were infused intrave nously with a solution of 75 mM K+ and 75 mM Na+, 150 mM Na+ or 300 mM Nafor 150 min under anesthesia. Urinary KK activity was measured in urine col lected every 30 min. Renal KK secretion began to increase within the 30 min infusion of K+ solution and persisted at more elevated levels during the i nfusion with K+ solution than with Na+ solutions. Furthermore, rats were gi ven intravenous injection of ATP-sensitive K+ channel blocker, either PNU-3 7883A (4-morpholinecarboximidine-N-1-adamantyl-N'-cyclohexyl) at a concentr ation of 10 mg/kg or glibenclamide at 30 mg/kg. Renal KK secretion increase d 30 min after administration of both PNU-37883A and glibenclamide. In conc lusion, it may be that augmentation of renal KK secretion by K+ loading occ urred through an increase in urinary K+ excretion followed by the inhibitio n of K+ transport from ATP-sensitive K+ channels. (C) 1999 Published by Els evier Science B.V. All rights reserved.