ACUTE STRESS STIMULATES SECRETION OF GHRH AND SOMATOSTATIN INTO HYPOPHYSEAL PORTAL BLOOD OF CONSCIOUS SHEEP

The effects of acute stress on growth hormone (GH) secretion and the m echanisms involved in its changes have been investigated in sheep. An acute isolation-restraint stress induced a rapid and significant incre ase in jugular GH levels in 12 out of 14 rams. GH-releasing hormone (G HRH) and somatostatin secretion during the same stress were studied in 5 animals prepared for hypophysial portal blood collection. A 3.5-fol d increase in portal GHRH levels was observed concomitantly with a sli ght elevation in portal somatostatin. Portal corticotropin-releasing h ormone (CRH) and jugular cortisol plasma levels increased during the s ame stress. Our data suggest that an isolation-restraint stress stimul ates GH secretion in the sheep and that GHRH may be responsible for GH response.