Metabolic responses to epinephrine stimulation in goldfish hepatocytes: evidence for the presence of alpha-adrenoceptors.
The effect of epinephrine on various aspects of cellular metabolism was studied in hepatocytes from the goldfish Carassius auratus. Epinephrine increased cytosolic free calcium ([Ca2+](i)) from a baseline value of 108 +/- 22 nM to a peak value of 577 +/- 127 nM in suspensions of hepatocytes. Responses of single cells ranged from a single spike (66% of hepatocytes) to variable oscillatory patterns (34%). The increase in [Ca(2+)](i) was independent of the presence of extracellular Ca2+ and was prevented by the alpha-adrenergic antagonist phentolamine. Cellular glucose release induced by epinephrine (1.7- to 3.2-fold) was significantly reduced in Ca2+-depleted cells and in the presence of phentolamine, providing evidence for the co-occurrence of alpha-adrenoceptors and a Ca2+-independent, presumably beta-adrenergic, system in these cells. Furthermore, epinephrine stimulated oxygen consumption in a Ca2+-dependent manner, which was not due to stimulated Na(+) pump activity. An increased rate of acid secretion of 50%, evoked by epinephrine, appears to be mediated by enhanced Na(+)/H(+) exchange but did not result in intracellular alkalization.
Krumschnabel
G
G
Institut für Zoologie und Limnologie, Abteilung für Okophysiologie, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria. Gerhard.Krumschnabel@uibk.ac.at
Manzl
C
C
Schwarzbaum
P J
PJ
D000143:Acids / Q000378:metabolism; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004837:Epinephrine / Q000494:pharmacology*; D005947:Glucose / Q000378:metabolism; D006054:Goldfish / Q000502:physiology*; D022781:Hepatocytes / Q000187:drug effects*; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*
D000143:Acids; D000316:Adrenergic alpha-Agonists; D011942:Receptors, Adrenergic, alpha; D019344:Lactic Acid; D005947:Glucose; D002118:Calcium; D004837:Epinephrine