Lithium-induced nephrogenic diabetes insipidus: in vivo and in vitro studies

The physiological basis for the polyuria and polydipsia occurring in some manic-depressive patients treated with lithium salts was studied in vivo and in vitro. Three lithium-treated polyuric patients, in whom other causes of a concentrating defect were excluded, had abnormal urinary concentrating abilities after a standard water depreviation test. Two of these patients failed to respond to exogenous vasopressin (ADH) and one had a subnormal response. The abilities of these patients to excrete solute-free water (C(H2O)) was comparable to normal subjects during steady-state water diuresis, suggesting no gross abnormalities in sodium transport. However, each of these patients demonstrated abnormally low capacities to reabsorb solute-free water (T(C) (H2O)) under hydropenic conditions after administration of hypertonic saline and vasopressin. These in vivo findings demonstrate at least a nephrogenic basis for the diabetes insipidus syndrome manifested by these three patients. The defect in water transport was further characterized in toad urinary bladders in vitro. Short-circuit current (I) and water flow (W) were studied under basal, ADH-stimulated, and cyclic adenosine 3',5'-monophosphate (c-AMP)-stimulated conditions. Increasing mucosal [Li(+)] progressively inhibited basal I, and both I and W induced by ADH. Significant inhibition of basal and ADH-induced I was observed at mucosal [Li(+)] < 1.1 mEq/liter, and of ADH-induced W at mucosal [Li(+)] = 11 mEq/liter. On the other hand, at these lithium concentrations, neither c-AMP-stimulated W nor I was inhibited. Increasing serosal [Li(+)] produced significant inhibition of basal I only at [Li(+)] at least 50-fold greater than at the mucosal (urinary) surface. These in vitro studies confirm that mucosal lithium inhibits the action of ADH, but not c-AMP. Hence, lithium appears to be a significant inhibitor of ADH-stimulated water flow, probably acts from the urinary surface, and appears to exert its effect at a site biochemically proximal to c-AMP action.

Renal effects of long term administration of triamcinolone acetonide in normal dogs

Triamcinolone acetonide was administered in excessive dosage to dogs to study the renal mechanism responsible for polyuria which is a clinically undesirable side effect of long term glucocorticoid therapy.Polyuria occurred coincident with a significant increase in urinary solute output. Although continuous administration of triamcinolone acetonide at 0.1 or 0.2 mg/lb/day caused a small but significant increase in creatinine output, the primary mechanism for the polyuria was increased solute excretion. Associated with the polyuria was pronounced hyperphagia and polydipsia. The cause of the hyperphagia was not established. The increase in electrolyte excretion caused by this synthetic steroid was probably compensated for by the hyperphagia. Because all the dogs showed muscle weakness and loss of body condition, it is likely that alteration in protein and amino acid metabolism was responsible for the hyperphagia.