The plasma membrane of Xenopus laevis oocytes contains voltage-dependent anion-selective porin channels

Recent patch-clamp studies have shown that anti-porin antibodies, applied t o the external side of excised plasma membrane patches of mammalian astrocy tes, close chloride channels that are thought to be engaged in cell volume regulation. Frog oocytes are often used to study this basic cell function. Here we document the localisation of endogenous porin voltage-dependent ani on-selective channels in Xenopus laevis oocyte plasma membranes. In confoca l laser microscopy images a disjunctive pattern of fluorescing spots appear about 10 mu m apart. Labelling was prevented by preabsorption of the antib odies with synthetic peptides comprising the epitope of the antigen. Immune -gold marking of oocyte surfaces followed by silver enhancement of the gold particles lead to a plasma membrane labelling corresponding to that obtain ed by the confocal laser approach. The data suggests the presence of voltag e-dependent, anion-selective channels in oocyte plasma membranes. This data should be borne in mind when frog oocytes are used to study the characteri stics of endogenous or heterologously expressed ion channels or regulatory proteins. (C) 2000 Elsevier Science Ltd. All rights reserved.