Plasma beta‐endorphin and adrenocorticotrophin in young horses in training

Abstract

A controlled period of submaximal exercise on a treadmill was used as a standardised stress test in 6 young horses to monitor the effects of training. Circulating plasma concentrations of immunoreactive beta-endorphin (IR beta-EP) were measured before, during and after the exercise period. The stress test was conducted on 3 occasions during an intensive training program lasting 14 weeks. In week 3 a marked increase in plasma IR beta-EP (P = 0.003) was demonstrated as a result of training, but by the last exercise test performed in week 9 no significant increase in plasma IR beta-EP concentrations could be detected. During the training period the basal concentrations of plasma IR beta-EP significantly decreased (P = 0.0059). Plasma adrenocorticotrophin (ACTH) did not increase during exercise, although there was a trend of decreasing basal plasma ACTH by the end of the training period. It was concluded that a standardised work test acted as a mild stress to unfit horses, but as the horses' fitness increased the hormonal response to exercise diminished. Basal plasma beta-EP concentrations were decreased with increasing fitness.

Plasma Adrenocorticotropin Concentration in Healthy Horses and in Horses With Clinical Signs of Hyperadrenocorticism

“…However, recent evidence suggests that training does not affect a horse's response to exogenous ACTH. 19,26 Conversely, one cushingoid pony had a cortisol increase factor of only 1.3 in spite of a high plasma ACTH concentration (60.2 pg/mL). This finding is consistent with a study by Heinrichs et alZ7 who reported that only 4 of 19 horses with histological evidence of pituitary adenoma had adrenal hyperplasia.…”

Circulating β-Endorphin, Adrenocorticotropin, and Cortisol Concentrations of Horses Before and After Competitive Show Jumping with Different Fence Heights

“…In athlete horses, the secretion of b-endorphin, ACTH, and cortisol is exclusively or partially dependent on type, intensity, and duration of exercise [1,6,[21][22][23][24][25][26][27][28][29] or on their interactions [30], as well as on the state of individual fitness [17,31], level of training [32][33][34][35], and age of horses [2,22,36].…”

Melanocortins Mimic the Effects of Leptin to Restore Reproductive Function in Lean Hypogonadotropic Ewes

“…β-END concentrations in ARC extracts (1:100) were measured in duplicate as previously described [41]. β-END (Bachem, Bubendorf, Switzerland) was iodinated using the chloramine T procedure [42] and purified by reverse-phase chromatography using a C18-sep-pak column equilibrated with 80% MeOH and 1% FA.…”