CULTURE OF EMBRYONIC RENAL COLLECTING DUCT EPITHELIA IN A GRADIENT CONTAINER

During organogenesis the ampullar epithelium of the renal collecting d uct acts as an inducer which generates all of the nephron anlagen. As development proceeds, one part of the collecting duct cells in the amp ullar tip retain their inducer capability, while others develop into t he functional epithelium consisting of principal and intercalated (IC) cells. The events leading from the embryonic inducer to the mature ti ssue are unknown. We investigated the maturation of embryonic collecti ng duct epithelium derived from neonatal rabbit kidney under in vitro conditions. To prevent dedifferentiation the epithelia were cultured o n kidney-specific support material within a tissue carrier. Apical and basal compartments of the epithelia were simulated in a gradient cult ure container. The two sides of the epithelium were each constantly pe rfused with a different medium. During the 14-day incubation the tissu e was not subcultured. The development of collecting duct cell feature s was investigated with morphological and immunohistochemical methods. Both light and electron microscopy revealed morphologically intact ep ithelia following gradient culture. The polarized cells rested on a un iformly developed basement membrane. The continuous application of ald osterone during the culture modulated the development of collecting du ct cell characteristics. Both basal and luminal administration of aldo sterone initiated differentiation in the embryonic epithelia. Using th e sodium (Na) channel blocker amiloride, it was demonstrated that Na c hannels are involved in the differentiation of the IC cell phenotype.