Effect of Ouabain in vivo on Corticosterone Secretion of Rat Adrenal Gland

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Chronic administration of ouabain to the intact rat in a daily dose of 3mg/kg b.w. for the consecutive 15 days caused a signicant increase of adrenal weight and a remarkable elevation of serum corticosterone associated with a signicant decrease of adrenal corticosterone. The same result was obtained with the hypophysectomized rat received the 5 consecutive ouabain-administrations combined with the 4 consecutive administrations of 0.1 unit of ACTH and with hypophysectomized rat received the consecutive 14 ouabain-administrations prior to hypophysectomy. Subcellular distribution of adrenal corticosterone was influenced to a minor extent by chronic administration of ouabain. Fate of corticosterone in chronically ouabain-treated rat was investigated by giving ³H-corticosterone intraperitoneally immediately after the last administration followed by pursuing ³H-corticosterone both in serum and in liver 30, 60 and 90min after the injection. Both 60 and 90min after the injection of 3H-corticosterone, the radioactivity of ³H in serum of ouabain-treated rat was higher than that of the control rat, while the specic radioactivity (³H/μg corticosterone) was lower in the drug-treated rat than in the control rat. Radioactivity in corticosterone fraction of liver did not show any difference between the drug-treated rat and the control rat.
From data obtained, it is reasonable to consider that chronic administration of ouabain to the rat gives influence not only on pituitary gland to stimulate the secretion of adrenocorticotropic hormone but also on adrenal gland to stimulate the secretion of adrenal corticosterone. Metabolism of corticosterone by liver will not be so much affected by chronic treatment of ouabain as the disturbance in the metabolism of this steroid will cause a signicant elevation of serum corticosterone.