Renal Handling of Sodium and Potassium in Cadmium Exposed Rats

Effects of cadmium exposure on renal $Na^+$ and $K^+$ transports were studied in rats. During the course of cadmium treatment (2 mg Cd/kg/day, s.c. injections for 3 weeks) renal tubular transports of $Na^+$ and $K^+$ were evaluated by lithium clearance technique. During the early phase (first week) of cadmium treatment, urinary $Na^+$ excretion decreased drastically and this was due to an increased $Na^+$ reabsorption both in the proximal and distal nephrons. During the late phase (third week) of cadmium treatment, filtered $Na^+$ load was decreased by reduction in GFR, but the renal $Na^+$ excretion returned to the control level due to impaired $Na^+$ transport in the proximal tubule. Urinary excretion of $K^+$ did not change during the early phase, but it rose markedly during the late phase of cadmium treatment. These results indicate that a light cadmium intoxication induces a $Na^+$ retention, and a heavy intoxication results in a $K^+$ loss. Possible mechanisms for these changes are discussed.