Developmental programming of the adrenocortical stress response by yolk testosterone depends on sex and life history stage

Abstract

Developmental exposure of embryos to maternal hormones such as testosterone (T) in the avian egg influences the expression of multiple traits, with certain effects being sex-specific and lasting into adulthood. This pleiotropy, sex dependency, and persistency may be the consequence of developmental programming of basic systemic processes like adrenocortical activity or metabolic rate. We investigated if experimentally increased in ovo exposure to T influences hypothalamus-pituitary-adrenal function, i.e. baseline and stress-induced corticosterone (Cort) secretion, and resting metabolic rate (RMR) of adult male and female House sparrows (Passer domesticus). In previous experiments with this passerine bird we demonstrated effects of embryonic T exposure on adult agonistic and sexual behavior and survival. Here we report that baseline Cort levels and the stress secretion profile of Cort are modified by in ovo T in a sex-specific and life-history stage dependent manner. Compared to controls, males from T-treated eggs had higher baseline Cort levels whereas females from T-treated eggs showed prolonged stress-induced Cort secretion during the reproductive but not the non-reproductive phase. Adult RMR was unaffected by in ovo T-treatment but correlated with integrated Cort stress secretion levels. We conclude that exposure of the embryo to T programs the hypothalamus-pituitary-adrenal axis in a sex-specific manner that in females depends, in expression, on reproductive state. The modified baseline Cort levels in males respectively stress-induced Cort levels in females may explain some of the long-lasting effects of maternal T in the egg on behavior and could be linked to previously observed reduced mortality of T-treated females.