Adrenergic modulation of Ca2+ homeostasis in isolated fish hepatocytes.
Isolated hepatocytes of the American eel (Anguilla rostrata LeSueur) and brown bullhead (Ictaluras nebulosus) have been used to characterize the effects of alpha- and beta-adrenergic agonists (epinephrine, phenylephrine, isoproterenol) and antagonists (phentolamine, propranolol) on calcium flux (influx, efflux) and cytosolic free calcium concentrations ([Ca2+]i). Bullhead hepatocytes have higher influx but lower efflux of Ca2+ than eel hepatocytes, which may relate to the primary source for changes in [Ca2+]i. Adrenergic agonists did not affect influx, but significantly enhanced efflux in eel hepatocytes (not bullhead) and [Ca2+]i in both species. Increases in efflux and in [Ca2+]i were blocked by alpha-antagonists (phentolamine) but not beta-antagonists (propranolol) when present in 100-fold excess of the agonist. Isoproterenol had no significant effect on either parameter tested. This study supports our hypothesis that liver cell Ca2+ homeostasis is modulated by alpha-adrenoceptor-linked pathways in these two fish species as has been previously demonstrated for the rat.
Zhang
J
J
Department of Biology, University of Ottawa, Ontario, Canada.
Désilets
M
M
Moon
T W
TW
D000704:Analysis of Variance; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004524:Eels / Q000502:physiology*; D004837:Epinephrine / Q000494:pharmacology; D006706:Homeostasis / Q000187:drug effects; D007059:Ictaluridae / Q000502:physiology*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008099:Liver / Q000378:metabolism*; D010646:Phentolamine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011941:Receptors, Adrenergic / Q000502:physiology; D013564:Sympathetic Nervous System / Q000502:physiology*
D011941:Receptors, Adrenergic; D010656:Phenylephrine; D011433:Propranolol; D007545:Isoproterenol; D002118:Calcium; D004837:Epinephrine; D010646:Phentolamine