Cyclic
AMP and furosemide stimulate the Na(+)-K(+) ATPase in isolated rat jejunal
cells.
Kreydiyyeh SI.
Department of Biology, Faculty of Arts and Sciences, American University of
Beirut, Beirut, Lebanon.
The effect of cAMP on the activity of Na(+)-K(+) ATPase in the rat jejunum was
studied by measuring the ouabain-sensitive (86)Rb accumulation by isolated
villus cells. The cyclic nucleotide increased significantly (86)Rb accumulation
by the enterocytes. The involvement of the NaKCl(2) symporter, the H(+)-K(+)
exchanger and the Na(+)-K(+) pump was tested by measuring, respectively the
furosemide-sensitive, the omeprazole sensitive, and the ouabain-sensitive (86)Rb
accumulation. Furosemide significantly increased the basal level of
intracellular (86)Rb and exerted overlapping effects with cAMP. Inhibiting the
Na(+)-H(+) exchanger with amiloride, decreased the basal level of intracellular
(86)Rb, and in its presence the stimulatory effect of cAMP was still observed
but not that of furosemide. cAMP and furosemide did not exert any significant
effect on (86)Rb accumulation by the enterocytes in presence of ouabain or in
the absence of sodium but their stimulatory effect still appeared in the absence
of chloride or in the presence of omeprazole or K(+)-channel blockers. These
data suggest that cAMP and furosemide stimulate the Na(+)-K(+) ATPase in rat
jejunal cells, and that this effect is, in the case of furosemide, mediated by
an activation of the Na(+)-H(+) exchanger. Copyright 2000 Academic Press.
Back
|
