Cyclic AMP and furosemide stimulate the Na+-K(+)ATPase in isolated rat jejunal cells

The effect of cAMP on the activity of Na+-K+ ATPase in the rat jejunum was studied by measuring the ouabain-sensitive Rb-86 accumulation by isolated v illus cells. The cyclic nucleotide increased significantly Rb-86 accumulati on by the enterocytes. The involvement of the NaKCl2 symporter, the H+-K+ e xchanger and the Na+-K+ pump was tested by measuring, respectively the furo semide-sensitive, the omeprazole sensitive, and the ouabain-sensitive Rb-86 accumulation. Furosemide significantly increased the basal level of intrac ellular Rb-86 and exerted overlapping effects with cAMP. Inhibiting the Na-H+ exchanger with amiloride, decreased the basal level of intracellular Rb -86, and in its presence the stimulatory effect of cAMP was still observed but not that of furosemide. cAMP and furosemide did not exert any significa nt effect on Rb-86 accumulation by the enterocytes in presence of ouabain o r in the absence of sodium but their stimulatory effect still appeared in t he absence of chloride or in the presence of omeprazole or K+-channel block ers. These data suggest that cAMP and furosemide stimulate the Na+-K+ ATPas e in rat jejunal cells, and that this effect is, in the case of furosemide, mediated by an activation of the Na+-H+ exchanger. (C) 2000 Academic Press .