Effect of norepinephrine on NaCl extrusion in guinea-pig kidney cortex slices
Proverbio, F.; Yaris, G.I.; Proverbio, T.; Marín, R.
Acta Cientifica Venezolana 37(5): 519-525
1986
ISSN/ISBN: 0001-5504 PMID: 2834904 Document Number: 278945
Guinea-pig kidney cortex slices (rich in proximal tubes), chilled in a medium without K+ and incubated at 25.degree.C in a medium with K+ extrude Na+ actively in two modes: 1) accompanied by Cl- and water and 2) in exchange for K+. In the presence of 1 mM Ca2+, addition to the bathing medium of norepinephrine (1 .times. 10-6 M) or the Ca2+ ionophore A-23187, induces a transient inhibition of net Cl- and water extrusion, together with a transient inhibition of net K+ gain. The presence of Ca2+ is essential to obtain the norepinephrine effect, and, even more, a similar effect is produced by high Ca2+ concentrations (5 mM) in the incubation medium. Ethacrynic acid, inhibits the net extrusion of NaCl by the slices, either in the absence or in the presence of norepinephrine. On the other hand, this NaCl movement, is insensitive to ouabain, which totally inhibits the Na+-K+ exchange. It is concluded that the found results could be explained considering that norepinephrine produces a stimulatory effect on the ethacrynic acid and furosemide sensitive Na-pump, and a partial inhibitory effect on the ouabain-sensitive, Na, K-pump. These effects would be associated to a transient increase of the cytoplasmic Ca2+.