Voltage-dependent stimulation of the Na(+)-K(+) pump by insulin in rabbit cardiac myocytes.
Insulin enhances Na(+)-K(+) pump activity in various noncardiac tissues. We examined whether insulin exposure in vitro regulates Na(+)-K(+) pump function in rabbit ventricular myocytes. Pump current (I(p)) was measured using the whole-cell patch-clamp technique at test potentials (V(m)s) from -100 to +60 mV. When the Na(+) concentration in the patch pipette ([Na](pip)) was 10 mM, insulin caused a V(m)-dependent increase in I(p). The increase was approximately 70% when V(m) was at near physiological diastolic potentials. This effect persisted after elimination of extracellular voltage-dependent steps and when K(+) and K(+)-congeners were excluded from the patch pipettes. When [Na](pip) was 80 mM, causing near-maximal pump stimulation, insulin had no effect, suggesting that it did not cause an increase in membrane pump density. Effects of tyrphostin A25, wortmannin, okadaic acid, or bisindolylmaleimide I in pipette solutions suggested that the insulin-induced increase in I(p) involved activation of tyrosine kinase, phosphatidylinositol 3-kinase, and protein phosphatase 1, whereas protein phosphatase 2A and protein kinase C were not involved.
Hansen
P S
PS
Department of Cardiology, Royal North Shore Hospital, St. Leonards, New South Wales 2065, Australia.
Buhagiar
K A
KA
Gray
D F
DF
Rasmussen
H H
HH
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006352:Heart Ventricles; D007211:Indoles / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009206:Myocardium / Q000201:enzymology*; D019319:Okadaic Acid / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011817:Rabbits; D012964:Sodium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D020032:Tyrphostins / Q000494:pharmacology; D000077191:Wortmannin
D000730:Androstadienes; D004791:Enzyme Inhibitors; D007211:Indoles; D007328:Insulin; D008301:Maleimides; D019319:Okadaic Acid; D019869:Phosphatidylinositol 3-Kinases; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D020032:Tyrphostins; D000077191:Wortmannin; C079836:tyrphostin 25; C088060:bisindolylmaleimide