Abstract
The effect of epinephrine on the activity of the Na +-K + ATPase was studied in isolated rat jejunal cells. The activity of the pump was assessed by measuring the ouabain inhibitable K + accumulation by the enterocytes using 86Rb as a tracer. Epinephrine stimulated significantly the Na +-K + ATPase in crypt cells but not in villus cells. This effect was still apparent in presence of propranolol and prazocin but disappeared in presence of yohimbine. Amiloride did not affect the epinephrine-induced stimulation. Calcium channel blockers and dibutyryl cAMP enhanced the activity of the pump, and exerted respectively overlapping and additive effects with epinephrine, when added simultaneously. The calcium ionophore A23187 inhibited the basal activity of the ATPase and the stimulatory effect of epinephrine disappeared in its presence. These results suggest that epinephrine stimulates the Na +-K + ATPase in jejunal crypt cells by activating α 2 receptors and decreasing intracellular calcium, and not by altering cAMP levels.
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