0854 Effects of stress on IGF-1 plasma concentrations and on expression of GH and IGF-1 receptors in mammary glands

Abstract

Growth hormone (GH) and insulin-like growth factor-1 (IGF-1) have positive effects on lactation. The action of these hormones on mammary tissue can be regulated by their respective receptors, GHR and IGF-1R. When females undergo a situation of stress during the lactation period, its influence on the expression of these receptors, as well as on concentrations of IGF-1 in the blood, is unknown. The objective of this study was to evaluate the effects of cortisol on IGF-1 plasma concentrations and on the expression of IGF-1R and GHR at the peak and end of lactation. Thirty Saanen goats were distributed in two groups: ACTH administration to induce stress (cortisol group) or placebo (control group), at peak (60 d) and end (180 d) of lactation. Four goats from each group were submitted to a mammary biopsy after 60 min of treatment administration. Mammary tissue was collected to measure mRNA levels for IGF-1R and GHR via RT-PCR, and IGF-1 plasma concentrations were measured (EIA method) in blood samples of goats collected at the time of biopsy. Statistical analyses were performed using ANOVA. There was no treatment effect (P > 0.10) on GHR or IGF-1R gene expression or on IGF-1 plasma concentrations at 60 d and 180 d of lactation. These results suggest that an increase in concentrations of cortisol in the bloodstream does not influence GHR and IGF-1R expression in the mammary gland. In addition, IGF-1 plasma concentrations remained constant in both groups during lactation.