Adrenalectomy and glucocorticoid administration in vivo do not affect production of 6-oxoprostaglandin F1 alpha by rat aortae.

1. Rats were bilaterally adrenalectomized and treated for periods of up to 32 days with doses of dexamethasone equivalent to physiological and supraphysiological endogenous glucocorticoid secretion. Aortic production of 6-oxoprostaglandin F1 alpha (6-oxo-PGF1 alpha) was measured by radioimmunoassay of the supernatant fluid from rings of aorta incubated in vitro. 2. Up to 32 days after adrenalectomy, neither adrenalectomy nor dexamethasone (2 micrograms/day and 20 micrograms/day) influenced aortic 6-oxo-PGF1 alpha production. 3. High doses of dexamethasone (60 micrograms/day for 6 days) in the presence or absence of mineralocorticoid (11-deoxycorticosterone, 600 micrograms/day) had no effect on aortic 6-oxo-PGF1 alpha production. 4. In contrast to the lack of effect of dexamethasone administered in vivo, incubation of aortic discs for 5 h with dexamethasone (1 mumol/l) in vitro caused inhibition of aortic 6-oxo-PGF1 alpha production to 23% of control levels. 5. Alteration in endogenous glucocorticoid secretion is unlikely to be involved in the physiological regulation of aortic 6-oxo-PGF1 alpha production.