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 × 105 or 106 cells/tube) were isolated from laying turkeys and incubated in 1.0 ml of M-199. In Experiment 1, 10-7M 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 10-6M 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 μg/106 cells, respectively. PRL mRNA abundance was significantly (P < 0.01) increased in only 10-6M PMA treatmemt. In Experiment 3, PKC desensitization decreased VIP-stimulated PRL release from 10.0 ± 2.3 to 4.2 ± 0.6 μg/5 × 105 cells and PMA-induced release from 7.1 ± 1.3 to 2.7 ± 0.3 μg/5 × 105 cells. VIP and PMA up-regulated PRL mRNA abundance was decreased two- to fourfold by PKC desensitization. In Experiment 4, 10-6M staurosporine (ST; PKC antagonist) decreased both 10-7M VIP-stimulated PRL secretion from 7.86 ± 2.9 to 2.43 ± 0.5 μg/5 × 105 cells and 10-8M PMA-stimulated PRL secretion from 4.26 ± 0.2 to 2.23 ± 0.3 μg/5 × 105 cells (P < 0.01). In addition, ST decreased VIP-stimulated PRL mRNA abundance from 15.95 ± 2.18 to 11.35 ± 2.27 AOU in VIP- and from 6.36 ± 1.21 to 4.57 ± 0.63 AOU in PMA-treated cells. Intracellular pituitary PRL content did not differ in any treatment (P > 0.05). In conclusion, these results suggest that the PKC second messenger system is involved in VIP-stimulated PRL release and gene expression in primary turkey pituitary cell culture.