Effects of VIP and GRF on the release of growth hormone in perifused bovine adenohypophysis.
The effects of vasoactive intestinal polypeptide (VIP) and growth hormone releasing factor (GRF:hpGRF(1-29)-NH2) on the release of growth hormone (GH) from anterior pituitaries from cows were examined by using an in vitro superfusion system. The pituitaries were excised randomly from cycling cows, dissected to obtain medial portions, and minced to obtain cubes with approximate dimensions of 1.5mm on a side. For each perifusion setup, 5 pieces of pituitary tissues were chambered and flushed with modified KRB solution saturated with 95% O2-5% CO2 at 38C. Perifusion with media containing 10(-6) and 10(-7)M VIP for 30 min induced a significant release of GH during the treatments (P less than 0.05). VIP (10(-8)M) increased GH levels significantly (P less than 0.05), but to a minor degree. Perfusion with the media containing 10(-6), 10(-7) and 10(-8)M GRF for 30 min markedly increased the GH concentration and the effects continued up to 90 min after termination of the perifusion of the peptide (P less than 0.05, P less than 0.01). The GH releasing effects of GRF could be seen at doses as low as 10(-11)M GRF (P less than 0.05, P less than 0.01). These findings indicate that the GH releasing effect of VIP is less potent than that of GRF in cows.
Hashizume
T
T
Laboratory of Animal Reproduction, Faculty of Agriculture, Iwate University, Morioka, Japan.
Kanematsu
S
S
D000818:Animals; D002417:Cattle; D046508:Culture Techniques; D005260:Female; D013006:Growth Hormone / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*
D014660:Vasoactive Intestinal Peptide; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone