Sodium and Water Transport in Kidney Proximal Tubular Cells

Richards and his group showed, about 40 yr ago, that the blood is filtered in the glomerulus. The largest portion of the water and solutes of the filtered fluid is absorbed across the proximal tubular wall, toward the peritubular blood capillaries (see 17). Thus, proximal tubular absorption is a process of paramount importance in the maintenance of homeostasis (1, 16). I shall review here studies on the way in which this absorptive process is accomplished and refer to new experiments on the nature of the sodium pump in kidney proximal tubular cells.