Localization of several G-protein subunits to the apical and basolateral membranes of cortical tubular cells from the rat kidney.

Dopamine was shown to affect Na+,K(+)-ATPase activity in basolateral membranes of the rat kidney via a pertussis toxin dependent mechanism. In order to examine if some form of pertussis toxin sensitive G-protein is present exclusively in the basolateral membrane of the rat renal cortex we examined the G-protein composition of both apical and basolateral membrane vesicles. Western blots showed an essentially uniform distribution of G alpha total, G alpha S and G beta over the two membranes. Go could not be detected with western blot technique in the vesicle preparations. By contrast, the distribution of ADP-ribosylation with the bacterial toxins pertussis toxin and cholera toxin depended on the amount of detergent in the assay and perhaps other factors, and thus could not be used to evaluate the relative amounts of G-protein subunits. Thus, in contrast to the situation in cultured renal cells, unequal distribution of receptor and G-protein substrates is apparently not paralleled by an unequal distribution of the detected forms of G-proteins under physiological conditions.