Effect of insulin on potassium secretion in rabbit cortical collecting ducts.
Insulin is known to play an important role in the regulation of extrarenal K homeostasis. Previous clearance studies have shown that insulin decreases urinary K excretion, but the responsible nephron segments have not been identified. In this microperfusion study, in vitro, the effect of insulin on K transport in the cortical collecting duct (CCD), which is thought to be an important segment for regulation of the final urinary K excretion, was investigated. Basolateral insulin (10(-6) M) significantly inhibited net K secretion by 20% (mean JK = -26.2 +/- 4.2 peq.mm-1.min-1 for controls compared with -21.1 +/- 3.4 with insulin, P less than 0.001) and depolarized the transepithelial voltage (VT, from -14.6 +/- 3.5 to -10.8 +/- 3.5 mV, P less than 0.005), recovery did not occur over 60 min. Insulin (10(-11)-10(-5) M) depressed K secretion and depolarized the VT in a concentration-dependent manner. The half-maximal concentration was 5 x 10(-10) M, which is within the physiological range of plasma insulin concentration. In tubules of deoxycorticosterone acetate-treated rabbits, insulin also produced a significant fall in K secretion (from -43.4 +/- 7.5 to -36.1 +/- 5.7 peq.mm-1.min-1, P less than 0.05). Although luminal Ba (2 mM) decreased K secretion (from -14.4 +/- 2.9 to -7.0 +/- 1.7 peq.mm-1.min-1), basolateral insulin (10(-6) M) inhibited K secretion further (to -4.7 +/- 1.3 peq.mm-1.min-1, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
Furuya
H
H
Department of Medicine, Jichi Medical School, Tochigi, Japan.
Tabei
K
K
Muto
S
S
Asano
Y
Y
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D017609:Barium Compounds; D002712:Chlorides; D003900:Desoxycorticosterone / Q000494:pharmacology; D004594:Electrophysiology; D005260:Female; D007328:Insulin / Q000494:pharmacology*; D007672:Kidney Cortex; D007685:Kidney Tubules, Collecting / Q000378:metabolism* / Q000502:physiology; D011188:Potassium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011817:Rabbits; D012964:Sodium / Q000378:metabolism
D017609:Barium Compounds; D002712:Chlorides; D007328:Insulin; C024986:barium chloride; D001464:Barium; D003900:Desoxycorticosterone; D000584:Amiloride; D012964:Sodium; D011188:Potassium