Protein kinase-C mediates chicken vasoactive intestinal peptide stimulated prolactin secretion and gene expression in turkey primary pituitary cells

Abstract

This set of experiments investigated the role of protein kinase-C (PKC) as a second messenger in vasoactive intestinal peptide (VIP)-stimulated prolactin (PRL) secretion and PRL mRNA abundance. Dispersed anterior pituitary cells (5 x 10(5) or 10(6) cells/tube) were isolated from laying turkeys and incubated in 1.0 ml of M-199. In Experiment 1, 10(-7) M VIP increased PRL secretion three- to fivefold. Prolactin mRNA abundance was higher in VIP-treated cells (11.45 +/- 2.11 arbitrary optical unit; AOU) than control cells (4.59 +/- 1.2 AOU). In Experiment 2, the addition of 10(-12), 10(-10), 10(-8), and 10(-6) M phorbol 12-myristate 13-acetate (PMA; PKC agonist) increased PRL release from 8.5 +/- 0.7 to 14.9 +/- 1.1, 17.2 +/- 1.3, 18.1 +/- 2.2, and 18.7 +/- 2.8 micrograms/10(6) cells, respectively. PRL mRNA abundance was significantly (P < 0.01) increased in only 10(-6) M PMA treatment. In Experiment 3, PKC desensitization decreased VIP-stimulated PRL release from 10.0 +/- 2.3 to 4.2 +/- 0.6 micrograms/5 x 10(5) cells and PMA-induced release from 7.1 +/- 1.3 to 2.7 +/- 0.3 micrograms/5 x 10(5) cells. VIP and PMA up-regulated PRL mRNA abundance was decreased two- to fourfold by PKC desensitization. In Experiment 4, 10(-6) M staurosporine (ST; PKC antagonist) decreased both 10(-7) M VIP-stimulated PRL secretion from 7.86 +/- 2.9 to 2.43 +/- 0.5 micrograms/5 x 10(5) cells and 10(-8) M PMA-stimulated PRL secretion from 4.26 +/- 0.2 to 2.23 +/- 0.3 micrograms/5 x 10(5) cells (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)