IGNIFICANCE OF GLUCOCORTICOID IN PREVENTINGHYPERCALCEMIC SHOCK IN RABBITS

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Abstract
Adrenalectomized rabbit are extremely susceptible to hyper-calcemia. Intravenous infusion of CaCl2 solution induced easily a lethal hypotention accompanied by cyanosis before cardiac disturbances due to extreme hypercalcemia ensued. Autopsy showed a pronounced dilatation of pulmonary artery and right heart, suggesting pulmonary arteriolar spasm. Examination of the cerebrospinal fluid in the shocked state revealed a marked elevation of Ca concentration. In intact animals no such elevation occurred and cardiac death followed in extreme hypercalcemia. Intracisternal injection of small amounts of CaCl2 solution in intact animals induced a quite similar type of shock observed in adrenalectomized animals in hypercalcemia. Bilateral cervical vagotomy could present the appearance of the shock, indicating that the shock was due to activation of pulmonary vagal vasoconstrictors. Pretreatment with glucocorticoid which completely reversed the increased susceptibility of adrenalectomized rabbits to intravenous infusion of CaCl2 solution was also effective in preventing the entrance of Ca ion into the cerebrospinal fluid. Hypercalcemic shock in the absence of glucocorticoid might be the result of the enhanced permeability of the blood-cerebrospinal fluid barrier to Ca ion. The significance of glucocorticoid for the maintenance of blood-cerebrospinal fluid barrier and the central action of Ca ion in this animal species were discussed.