Annual changes in plasma progesterone and estradiol-17β concentrations compared to pituitary-adrenal axis activity in the female goat reared under arid environment

Abstract

ABSTRACT This study investigates the relationships between the pituitary-adrenal axis and the ovarian activity in the cyclic goat reared under arid environment. Plasma hormone levels are assessed on blood samples collected weekly at 9:00 a.m., during one year. The ovarian activity is characterized by an anestrous period from mid-March to mid-July and a breeding period during the rest of the year. Adrenal histomorphometry and immunolocalization of Estrogen Receptors α (ERα) and Progesterone Receptors (PR) were performed on adrenal glands collected during each season. During the anestrous period, all adrenal compartments appeared enlarged, as did cellular and nuclear areas. ERα and PR immunostaining were identified in all the adrenal gland zonae with more intensity for the ERα. ERα immunostaining is greater in zona fasciculata whereas PR immunostaining is more intense in zona fasciculata and zona reticularis during the breeding season. Plasma ACTH shows no difference between the two seasons, while cortisol rises slightly during the anestrous period. There is a negative but not significant correlation between progesterone levels with plasma ACTH and cortisol. The pituitary-adrenal axis is activated essentially at the anestrous onset and at the ovarian resumption which represents stressful events, but it varies slightly between these two seasons in this goat.