PROLACTIN BINDING SITES IN XENOPUS LAEVIS (DAUDIN) (ANURA PIPIDAE) KIDNEY: AN AUTORADIOGRAPHIC AND IMMUNOCYTOCHEMICAL STUDY

SUMMARY We have studied prolactin binding sites in Xenopus laevis (Daudin) (Anura Pipidae) kidney by autoradiography and immunocytochemistry. By the autoradiographic technique after intracardiac injection of 125I- oPRL labelling is appreciable in Xenopus laevis kidney at the level of the large vessels and capillaries, the renal corpuscle and, to a variable extent, within the lumina and epithelial cells of the proximal convoluted tubules. Compared to the autoradiographic reaction, the immunocytochemical method failed to reveal the hormone when extremely low doses of it were injected but allowed a much more exact localization of prolactin uptake by the epithelial cells of the proximal convoluted tubules. On the basis of the autoradiographs we could not ascertain wheter, or to what extent, the hormone was bound to specific renal cell PRL receptors: in fact, not only insulin and luteinizing hormone, but also unlabelled prolactin, injected as a specific competitor, failed to bring about the recognizable displa...