Secretion of endogenous ouabain from bovine adrenocortical cells: role of the zona glomerulosa and zona fasciculata.

Recent experiments have demonstrated the secretion of a ouabain-like compound from primary cultures of bovine adrenocortical cells (1). To determine the relative contribution of the outer zones of the adrenal cortex to the secretion of endogenous ouabain, we measured the content of this steroid in zona glomerulosa and zona fasciculata tissue freshly excised from bovine adrenals and in the secretion media of primary cell cultures derived from these zones. The tissue content of endogenous ouabain was 5.7-fold higher in the zona glomerulosa than in the zona fasciculata. The concentration of endogenous ouabain was 4.1-fold higher in 24-hour conditioned media from zona glomerulosa than in zona fasciculata cultures. Angiotensin II and ACTH stimulated the secretion of endogenous ouabain from zona glomerulosa cultures, but had no effect on zona fasciculata cultures. These findings suggest that endogenous ouabain is primarily synthesized and secreted from the adrenal zona glomerulosa.