[Intracellular localization and possible pathways of transcellular calcium transport in the cells of the proximal kidney tubules].

Cytochemical and ultrastructural studies of rat proximal tubule cells were carried out to elucidate possible ways of transcellular Ca2+-transfer. The bulk of cellular calcium was found in mitochondria. Calcium was also revealed in some pinocytic vesicles, in cisterns of the Golgi complex and of the smooth endoplasmic reticulum. The sections made parallel to apical-basal axis of cells showed that mitochondria stretch continuously from the apical to the basal plasma membrane. These data suggest that mitochondria may serve as conductors of Ca2+-fluxes from the apical to the basal plasma membranes through the proximal tubule cells.