Impact of maternal nutrition during pregnancy on pituitary gonadotrophin gene expression and ovarian development in growth-restricted and normally grown late gestation sheep fetuses

Abstract

The influence of maternal nutrition during pregnancy on anterior pituitary gonadotrophin gene expression and ovarian development in sheep fetuses during late gestation was investigated. Embryos recovered from superovulated adult ewes that had been inseminated by a single sire were transferred, singly, into the uteri of adolescent recipients. After embryo transfer, adolescent ewes were offered a high or moderate amount of a complete diet. Pregnancies were terminated at day 131 +/- 0.6 of gestation and the fetal brain, anterior pituitary gland and gonads were collected. Gonadotrophin gene expression (LHbeta and FSHbeta subunits) in the fetal pituitary gland was examined using in situ hybridization. Ovarian follicular development was quantified in haematoxylin- and eosin-stained ovarian sections embedded in paraffin wax. Six dams that were offered a high nutrient intake carried normal-sized fetuses (weight within +/- 2 SD of mean weight for control fetuses from dams fed a moderate level of complete diet) and 13 dams carried growth-restricted fetuses (weight +/- 2 SD of mean weight for control fetuses from dams fed a moderate level of complete diet). Mean placental masses in these groups were 354 +/- 24.5 and 230 +/- 21.1 g, respectively, compared with 442 +/- 54.3 g in the dams that were offered a moderate nutrient intake (n = 6). Growth-restricted fetuses from dams offered a high nutrient intake showed higher pituitary LHbeta mRNA expression (P < 0.05) than normal-sized fetuses from dams offered a moderate nutrient intake (252 +/- 21.6 and 172 +/- 23.6 nCi g(-1), respectively). FSHbeta mRNA expression was not influenced by growth status. Fewer follicles (primarily in the resting pool) were observed in the ovaries of both growth-restricted (P < 0.002) and normal-sized fetuses from dams offered a high nutrient intake (P < 0.01) compared with normal-sized fetuses from dams offered a moderate nutrient intake. Irrespective of nutritional treatment, the total number of follicles was positively associated with placental mass (P < 0.01). Thus, a high maternal nutrient intake during adolescent pregnancy had a negative influence on ovarian follicular development in fetuses as determined during late gestation.