Natriuretic and kaliuretic effects of central acute cadmium administration in rats

We studied the acute effects of cadmium third ventricle injections on renal excretion of water, sodium and potassium in rats previously submitted to an oral water load equivalent to 10% of their body weight. Injections of cadmium chloride (0.03, 0.3, and 3.0 nmol/rat) significantly increased sodium and potassium renal excretion without changing urine flow. Pretreatment with losartan, an angiotensin II AT1 receptor antagonist (10.8 nmol/rat into the third ventricle 10 min before central cadmium administration) inhibits the natriuretic effect of this metal, being unable to reverse its kaliuretic effect. Pretreatment with gadolinium, a calcium-channel blocker (0.3 nmol/rat into the third ventricle 20 min before central cadmium administration) abolishes both the natriuretic and the kaliuretic response of cadmium. The data clearly show that cadmium injections into the third ventricle disturb central regulation of renal function leading to an increased renal loss of sodium and potassium. It is also evident that the natriuretic action of the metal depends on an increase in brain angiotensin II release. Also, the functional integrity of calcium channels is required for the expression of both the natriuretic and the kaliuretic effects of the metal.