GHRP-6 in heifer and cow adenohypophisial cells separated by elutriation.
Previous studies have reported that the growth hormone (GH)-releasing peptide (GHRP-6), a synthetic Met-enkephalin peptide analog, stimulates GH release in vivo in a variety of species, including bovine. In the present study, the in vitro effects of GHRP-6 on bovine somatotropes separated by elutriation were analyzed as well as its interactions with the GH-releasing hormone (GHRH). The administration of GHRP-6 at doses from 10(-8) M to 10(-5) M stimulated GH release, and also 10(-9) M in cow pituitary cells, and produced maximal stimulation at 10(-6) M. The effects of GHRP-6 (10(-6) M) on GH release were shown at 1, 2, 3 and 4-h incubation (p < 0.05), except for heifer pituitary cells at 1-h incubation (p > 0.05). The GH releasing effects of either GHRH alone or GHRH+GHRP-6 were significantly more potent than that of GHRP-6 alone (p < 0.05). Contrary to what occurred in rat pituitary cells, the combined administration of 10(-6) M GHRP-6 with 10(-8) M GHRH did not result in a synergist action of GH release. Although the additive effect was significant when compared with GHRH alone (p < 0.05). The results demonstrate the existence of differences in the effect of GHRH+GHRP-6 on bovine somatotropes. These differences may reflect the physiological importance of distinct cell subpopulation, like the mammosomatotroph cells.
Rico
M
M
Departamento de Anatomía y Producción Animal, Facultad de Veterinaria, Universidad de Santiago de Compostela, Lugo, Spain.
Lorenzo
M T
MT
Pazo
J A
JA
Vega
F V
FV
De la Cruz
L F
LF
D000375:Aging / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D005260:Female; D007150:Immunohistochemistry; D009842:Oligopeptides / Q000302:isolation & purification / Q000378:metabolism*; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism*; D051381:Rats
D009842:Oligopeptides; C041048:growth hormone releasing hexapeptide