AJP - Cell Physiology, Vol 263, Issue 5 C1096-C1102, Copyright © 1992 by American Physiological Society
Alpha 1-adrenergic stimulation of Na-H exchange in cardiac myocytes
M. A. Wallert and O. Frohlich
Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322.
The activation of Na-H exchange in adult rat heart myocytes was
characterized in response to a phorbol ester (phorbol 12-myristate
13-acetate) and an alpha 1-adrenergic agonist [6-fluoronorepinephrine
(6F-NE)]. Transport activation was assessed by determining the initial rate
with which intracellular pH (pHi) was returned from an acid pulse and by
following changes in steady-state pHi; pHi was determined by a pH-sensitive
fluorescent dye. Both agonists shifted the intracellular pH dependence of
Na-H exchange by 0.10-0.15 pH units in the alkaline direction. This shift
was prevented by the presence of sphingosine and
1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7), inhibitors of protein
kinase C. The agonists also alkalinized pHi at steady state. The
alkalinization by 6F-NE was blocked by prazosin and H-7. This indicates
that the adrenergic stimulation of cardiac Na-H exchange is mediated by an
alpha 1-adrenergic mechanism and very likely involves the activation of
protein kinase C.
