Adrenocorticotropic hormone and cortisol response to corticotropin-releasing factor and lysine vasopressin in pigs1

Abstract

Two experiments were conducted to evaluate the ability of corticotropin-releasing factor (CRF) and lysine vasopressin (LVP) to stimulate the secretion of ACTH and cortisol in pigs. In Exp. 1, barrows were blocked by weight (average BW 97 +/- 1 kg) and received an i.v. bolus of 10 (n = 4), 50 (n = 4), or 100 (n = 3) micrograms of LVP. Samples of plasma were obtained at 10-min intervals for 2 h before and for 2 h after peptide treatment. The percentage of change in plasma concentration of ACTH (average of the concentration 1 h after LVP compared with the average of the 1 h before LVP) was greater (P < .001) for 100 micrograms (452.3 +/- 4.7%) than for 10 (81.5 +/- 5.7%) or 50 micrograms (233.6 +/- 11.3%). Furthermore, the ACTH response was greater (P < .001) to 50 micrograms than to 10 micrograms. The cortisol responses to treatment (average of the concentration 2 h after LVP compared to the average of the 2 h before LVP) were similar in pigs given 50 (132.8 +/- 5.3%) and 100 (123.2 +/- 2.4%) micrograms, but both were greater (P < .001) than the response to 10 micrograms (38.2 +/- 1.4%). In Exp. 2, a dose of LVP was chosen that provided a total mass of peptide similar to the lowest dose in Exp. 1, but this time the peptide was administered at .11 nmol/kg BW. This dose of LVP was chosen because it resulted in neither maximum ACTH nor cortisol secretion in Exp. 1.(ABSTRACT TRUNCATED AT 250 WORDS)