Insulin-specific receptor-mediated slowing of beat rate in embryonic heart cells

Abstract

Spheroidal aggregates of embryonic heart cells showed their spontaneous beat rate when exposed to insulin. The concentration that produced a half-maximal response (1.7 nM) corresponded to the dissociation constant of binding to a specific high-affinity insulin receptor. The pace-maker phase of action potentials recorded during insulin perfusion was preceded by a prolonged or flattened after hyperpolarization, and its slope was less steep than controls. The action potential duration was also prolonged. These results indicate that physiological concentrations of insulin can regulate the embryonic heart rate.

Insulin and the resting potential of hypoxic substrate-deprived myocardium

“…In embryonic chick heart cells, insulin causes a ouabain-insensitive hyperpolarization and increases a timeindependent background outwad cunent (Fischmeister ea al. 1983;DeHaan et al 1984). In mammalian myocardium (canine false tendons a d papillary muscle from rats and kittens) the hyperpalmizing effect of insulin is enhanced by Cs ions and prevented by cooling, pretreatment with cardiac glycosides, and previous exposure to hypoxic substrate-free medium (40-45 'Author to whom all correspondence should be addressed.…”

Heart & Cardiac Muscle

“…Time constants for decay were fitted by a modified Levenberg-Marquardt least-squares minimization algorithm (Dempster, 1993) (Freestone et al 1995). Vetter et al (1988) have also reported an increase in cardiac contractility in neonatal rat cardiac myocytes in culture due to these two agonists, whilst DeHaan et al (1984) have described a negative chronotropic effect of insulin on embryonic rat cardiac myocytes in culture. The chronotropic action of IGF-1 on cardiac cells has not been as well delineated, however.…”