CA2+ AND K+ ION EFFECTS ON ULTRASTRUCTURE OF ISOLATED FLOUNDER KIDNEY TUBULES

Marked structural changes were seen in the morphology of incubated flounder kidney tubular cells when potassium or calcium ions were omitted from the incubation medium. When potassium ions were omitted, changes occurred in the basal region of the cells. When calcium ions were omitted, changes were seen in the apical region including loss of the junctional complexes and rearrangement of the apical microvilli. Physiologists have shown that the active transport of chlorphenol red from bathing medium to tubular lumen in isolated flounder renal tubules appears to be a two-stage process (8, 10, 21, 24, 28). The first step involved movement of dye into the cell and was shown to be dependent on the presence of potassium ions. The second step involved movement of the dye into the tubular lumen and required the presence of calcium ions. The present morphologic studies suggest reasons for the lack of dye transport and accumulation in each case. © 1969 Academic Press, Inc.