EFFECT OF A HIGH NACL DIET ON THE ACTIVE MECHANISMS OF NA+ EXTRUSION IN RAT-KIDNEY

Healthy male rats were exposed to a chronic ingesta of an isotonic NaCl solution during a period of four months. Two different preparations were utilized to study the effect of this treatment on the active mechanisms of Na+ reabsorption of kidney proximal tubular cells: outermost kidney cortex slices (rich in proximal tubules) and inside-out basolateral plasma membrane vesicles prepared from the small tissue. It was found that the activity of the ouabain-insensitive, Na-pump of basolateral plasma membranes of kidney proximal tubular cells was increased in about 70%, whereas the ouabain-sensitive, Na,K-pump activity did not change with the experimental treatment. These results represent a strong support to the two Na-pump''s hypothesis since the treatment affected the Na-pump differentially without affecting the Na,K-pump.