Influence of corticosteroids on prolactin release from anterior pituitary cell aggregates cultured in serum-free medium. Differential effects on dopamine-induced inhibition, post-dopamine rebound and stimulation by TRH, vasoactive intestinal peptide (VIP), angiotensin II and isoproterenol.

Dispersed rat anterior pituitary cells were allowed to reassociate into spherical aggregates by gyrotory shaking in serum-free chemically defined culture medium. When aggregates were superfused after being cultured for 5 days in this medium, stimulation of PRL release by TRH, VIP, angiotensin II and the beta-adrenergic agonist isoproterenol was comparable to that of aggregates cultured in serum-supplemented culture medium. Addition to the serum-free medium of 80 nM dexamethasone (Dex) resulted in a significant enhancement of the stimulation of PRL release by TRH, VIP and angiotensin II but not of the stimulation of PRL release by isoproterenol. Dex also failed to influence the inhibition of PRL release by 10 min exposure to 10 nM dopamine (DA). However, Dex significantly enhanced the post-DA rebound secretion of PRL. After 3 weeks in culture Dex provoked a similar potentiation of the response to angiotensin as at 5 days in culture but it abolished almost completely the stimulatory effect of isoproterenol. It is concluded that pituitary cell aggregates cultured in defined serum-free medium are a reliable system to study the multifactorial control of PRL release. The data show that peptidergic, dopaminergic and beta-adrenergic control at the pituitary level is differentially modulated by corticosteroids.