Basal secretion of growth hormone in sheep is not influenced by GH feedback

Autoregulation of GH secretion in sheep was examined by intravenous and intracerebroventricular (ICV) administration of human and bovine GH. Intravenous administration of hGH at either 2 mg or 10 mg per sheep failed to alter radioimmunoassayable plasma ovine GH concentrations or plasma somatostatin. Human GH also failed to after plasma oGH when given at a dose of 50 mu g icv. Bovine GH (at 50 mu g or 500 mu g) ICV did not affect basal plasma oGH or somatostatin, nor did pretreatment with 50 mu g bGH significantly alter GH response to clonidine stimulation, although the change in plasma GH with stimulation was only half that of controls. These data do not support a major autoregulatory effect on GH secretion in the sheep. (C) 1997 Elsevier Science Inc.