Constitive growth hormone secretion in sheep after hypothalamopituitary disconnection and the direct in vivo pituitary effect of growth hormone releasing peptide 6

Abstract

The effect of hypothalamopituitary disconnection (HPD) on growth hormone (GH) secretion was studied in sheep. Plasma GH levels were measured in serial blood samples (10 min x 6-8 h) taken from 12 Romney wethers and 5 ewes which had undergone HPD 40-506 days earlier and from 4 wethers (10 min x 7 h) to serve as controls. Five wethers and 5 ewes were taken ~ 300 days after HPD and injected with vehicle or 10 μg/kg of the synthetic hexapeptide growth hormone-releasing peptide 6 (GHRP-6); GH responses were monitored. In a second series of sheep, 4 wethers and 6 HPD wethers were given saline. 0.5 μg/kg of synthetic growth hormone-releasing factor (GRF) or 5 μg/kg GHRP-6 and were blood-sampled to ..