Stimulation of Prolactin Secretion from Turkey Anterior Pituitary Cells in Culture

Abstract

Prolactin (PRL) secretion by monolayer cultures of turkey anterior pituitary cells was significantly increased (up to 44-fold) by vasoactive intestinal peptide (VIP), arginine vasotocin (AVT), and by an extract of turkey hypothalami (HE). Several other neuropeptides (including thyrotropin-releasing hormone) and neurotransmitters were ineffective in influencing PRL secretion at doses up to 10^-6 M. The dynamic PRL response to HE and VIP was studied using supervised pituitary cells attached to microcarrier beads. HE, administered in 30-min pulses, resulted in a significant, dose-related increase in PRL secretion from a basal secretion rate of 2.32 ng/min/10⁷ cells to a peak secretion rate of 127.13 ng/min/10⁷ cells at the highest dose of HE tested (1 mg tissue-equivalent weight/ml). VIP significantly increased PRL secretion at all doses studied (from 10^-10 to 10^-6 M), with 10^-8 M VIP producing a response similar to that observed with 1 mg/ml HE. A highly significant (P < 0.001) linear relationship was demonstrated between the log-dose of VIP administered and peak PRL secretion rate. These studies suggest that VIP, but not TRH, may be a physiological stimulus for PRL release in the turkey.