Metabolic responses to epinephrine-stimulation in goldfish hepatocytes: evidence for the presence of -adrenoceptors

KRUMSCHNABEL G, MANZL C, SCHWARZBAUM PJ

GENERAL AND COMPARATIVE ENDOCRINOLOGY

ACADEMIC PRESS INC ELSEVIER SCIENCE

Año: 2001 p. 205 - 213

0016-6480

The effect of epinephrine on various aspects of cellularmetabolism was studied in hepatocytes from the goldfishCarassius auratus. Epinephrine increased cytosolic freecalcium ([Ca21]i) from a baseline value of 108622 nM toa peak value of 577 6 127 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 [Ca21]i was independent of thepresence of extracellular Ca21 and was prevented by thea-adrenergic antagonist phentolamine. Cellular glucoserelease induced by epinephrine (1.7- to 3.2-fold) was significantlyreduced in Ca21-depleted cells and in the presenceof phentolamine, providing evidence for the co-occurrenceof a-adrenoceptors and a Ca21-independent,presumably b-adrenergic, system in these cells. Furthermore,epinephrine stimulated oxygen consumption in aCa21-dependent manner, which was not due to stimulatedNa1 pump activity. An increased rate of acid secretionof 50%, evoked by epinephrine, appears to be mediatedby enhanced Na1/H1 exchange but did not result inintracellular alkalization.