Ouabain-resistant hyperpolarization induced by insulin in aggregates of embryonic heart cells.
Spheroidal aggregates formed from trypsin-dissociated 14-day embryonic chicken hearts after 48 hr of rotation on a gyratory shaker. Intracellularly recorded resting membrane potentials of aggregates bathed in 1.3 mM K+ balanced salt solution had a mean (+/- SD) of 64 +/- 4 mV. After a stable potential was achieved, addition of 1-100 nM sodium bovine insulin caused a slow hyperpolarization of up to 19 mV after 4-5 min, followed, in some cases, by a further, more rapid, shift to a potential near EK. Equivalent hyperpolarizations were observed when insulin was added in the presence of 10 mM ouabain, indicating that enhanced Na+,K+ pump activity was not responsible for the change in membrane potential. The concentration of insulin that produced half-maximal hyperpolarization (2 nM) corresponded to the association constant of a high-affinity insulin receptor, suggesting that binding to this class of receptors led to the change in membrane potential. Steady-state current-voltage curves from current clamp experiments suggested that insulin produced an increase in slope conductance at potentials near rest by inducing an outward current with an apparent potential negative to -90 mV.
D000818:Animals; D002642:Chick Embryo; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D006321:Heart / Q000187:drug effects / Q000196:embryology / Q000502:physiology*; D007328:Insulin / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects*; D009206:Myocardium / Q000166:cytology / Q000201:enzymology; D010042:Ouabain / Q000494:pharmacology; D011972:Receptor, Insulin / Q000187:drug effects; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D007328:Insulin; D010042:Ouabain; D011972:Receptor, Insulin; D000254:Sodium-Potassium-Exchanging ATPase