VALIDATION OF A CULTURE SYSTEM FOR PORCINE PITUITARY-CELLS - EFFECTS OF GROWTH HORMONE-RELEASING FACTOR AND(OR) SOMATOSTATIN ON GROWTH-HORMONE SECRETION

The goal of the study was to establish the age-related responses of cultured porcine pituitary cells to growth hormone-releasing factor (GRF) and(or) somatostatin (SRIF). A culture system for dispersed porcine pituitary cells was validated. Pituitaries from female pigs of various ages (90 or 110 d of gestation, newborn, 3, 6, or 24 mo old) were enzymatically dispersed with collagenase and neuraminidase, plated (200,000 cells/well), and cultured for 3 d. Plated cells were then subjected to a 4-h challenge with increasing concentrations of GRF (10(-11) to 10(-8) M), SRIF (10(-9) to 10(-6) M), or 10(-8) M of each peptide with increasing concentrations of the other. Culture media were collected and assayed for growth hormone (GH). Pituitaries were pooled so that there were four replicates per age, and treatments were assigned to quadruplicate wells. Concentrations of GH in control wells (basal GH) were maximal at 110 d of gestation and decreased thereafter (P < .01) with increasing age of swine. All peptide combinations affected the GH response (P < .05) at all ages studied, yet GRF was more potent than SRIF in eliciting a response. Age had an effect (P < .05) on the GH response to any of the treatments; younger pigs (90, 110 d of gestation and newborns) had a greater response (P < .05) than older pigs (3, 6, and 24 mo), whereas 6- and 24-mo-old pigs responded similarly in all cases (P > .1). Developmental changes in the response to GRF given alone occurred during fetal life (between 90 and 110 d, P < .01) and between 3 and 6 mo of age (P < .01), whereas changes in the response to SRIF took place between 110 d of gestation and birth (P < .01). It can be concluded that GRF and SRIF elicit GH responses in cultured porcine pituitary cells from pigs of 90 d of gestation until 24 mo of age, but the magnitude of the response is greatly affected by age.