Calcium ion transport across plasma membranes isolated from rat kidney cortex.
Basal-lateral-plasma-membrane vesicles and brush-border-membrane vesicles were isolated from rat kidney cortex by differential centrifugation followed by free-flow-electrophoresis. Ca2+ uptake into these vesicles was investigated by a rapid filtration method. Both membranes show a considerable binding of Ca2+ to the vesicle interior, making the analysis of passive fluxes in uptake experiments difficult. Only the basal-lateral-plasma-membrane vesicles exhibit an ATP-dependent pump activity which can be distinguished from the activity in mitochondrial and endoplasmic reticulum by virtue of the different distribution during free-flow electrophoresis and its lack of sensitivity to oligomycin. The basal-lateral plasma membranes contain in addition a Na+/Ca2+-exchange system which mediates a probably rheogenic counter-transport of Ca2+ and Na+ across the basal cell border. The latter system is probably involved in the secondary active Na+-dependent and ouabain-inhibitable Ca2+ reabsorption in the proximal tubule, the ATP-driven system is probably more important for the maintenance of a low concentration of intracellular Ca2+.
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008954:Models, Biological; D051381:Rats; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology
D000255:Adenosine Triphosphate; D012964:Sodium; D002118:Calcium