CONSTITUTIVE 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 approximately 300 days after HPD and injected with vehicle or 10 micrograms/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 micrograms/kg of synthetic growth hormone-releasing factor (GRF) or 5 micrograms/..