Adrenal glomerulosa was examined for the presence of an adrenergic influence on aldosterone production. Cultured rat adrenal capsular explants were transferred to a perifusion system where the effect of exposure to catecholamines on aldosterone production was assessed. At 10-6 M, isoproterenol greater than epinephrine greater than norepinephrine significantly stimulated aldosterone production, whereas at 10-8 M only isoproterenol showed significant stimulation. Propranolol, a β-adrenoreceptor antagonist, inhibited stimulation by epinephrine, and the phosphodiesterase inhibitor, 1-methyl-3-isobutylxanthine, enhanced stimulation by a submaximal dose of epinephrine. Epinephrine and norepinephrine were found by radioenzymatic assay to be present in fresh as well as cultured capsular tissue, although levels were considerably lower in tissue that had been in culture (about one tenth that of fresh tissue). The epinephrine-norepinephrine ratio was similar in capsule and medulla, suggesting a medullary source of capsular catecholamines. Whether catecholamines in the capsule arose from the in vitro manipulation of adrenal tissue or existed in vivo is unclear. In summary, β-agonists stimulate aldosterone production in cultured rat capsular explants.
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