|Carroll, Jeffery - Jeff Carroll|
Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2000
Publication Date: N/A
Interpretive Summary: Stress is characterized by low blood levels of luteinizing hormone (LH), necessary for follicular growth and ovulation, elevated cortisol, stress hormone, growth hormone (GH), necessary for growth, and reduced feed intake. Stress results in slow growth, delayed puberty, irregular estrous cycles and failure of animals to breed. The recently discovered protein, urocortin, is produced in the brain and is secreted in response to stress. This is the report to demonstrate that administration of urocortin inhibited feed intake, LH secretion and stimulated GH and cortisol secretion in the pig. Therefore, understanding the interaction between urocortin and stress is necessary in order to develop new management practices to minimizes stress and promote efficient growth and reproduction.
Technical Abstract: In three experiments (Exp), ovariectomized gilts received intracerebroventricular (ICV; Exp 1 - with restraint, Exp 2 - without restraint) or intravenous (i.v.; Exp 3) injections of urocortin or saline to assess its effects on feed intake and serum GH, LH and cortisol. Following a 20 hr fast, feed was presented at 1 hr (Exp 1) or 30 min (Exp 2 and 3) after injection (time = 0 hr) of saline or 5 (U5) or 50 (U50 ug/pig (Exp 1 and 2) or 5 ug/kg BW (Exp 3) of urocortin. Treatment of gilts with U50 decreased feed intake, relative to saline treatment (treatment x time interaction; P<0.5), when delivered via ICV but not i.v. routes of administration. A treatment by time interaction was detected for GH (Exp 1,2,3) and LH (Exp 1 and 2; P<0.01). Serum GH increased over time (relative to -2 hr; P<0.05) following treatment of urocortin but not saline regardless of route of administration. Conversely, in Exp 1 (U5 and U50) and Exp 2 (U50), LH decreased relative to -2 hr although the decrease was delayed during Exp 1. Serum cortisol was not affected by treatment in Exp 1, but increased following urocortin in Exp 2 and 3 (treatment by time interaction, P<0.01). These data provide evidence that urocortin modulates GH and LH concentrations and suppresses feed intake in gilts via mechanisms which may be independent of ACTH and cortisol and may depend upon dose and route of administration.