Alterations of the pituitary - gonadal axis in the neonatal blue fox (Alopex lagopus) exposed to prenatal handling stress

Abstract

Handling is a stressor for blue foxes. The influence of preterm handling (1 min daily) of vixens was investigated in 68, 10-day-old cubs, 34 male and 34 female. Body, gonadal and pituitary weight, ano-genital distance, gonadal testosterone and oestradiol content and in vitro production, and pituitary LH content were measured in all cubs. The gonads were frozen or incubated in vitro with, or without, added hCG (2.5 IU per sample). The gonadal incubates and homogenates were analysed for testosterone and oestradiol by radioimmunoassay and the pituitary homogenates for LH by immunofluorometric assay. The results indicate that neonatal fox gonads actively produce steroids and that there are significant sex differences in basal steroid production and response of the gonads to hCG, and in pituitary LH content. Maternal stress resulted in a significant reduction of morphometric and hormonal measures of the reproductive system in neonatal blue foxes, with more drastic effects in female cubs. Gonadal weights were lower in cubs of both sexes from stressed vixens (65.7 4.3 v. 50.6 1.8 mg for the ovaries and 23.2 1.0 v. 17.7 1.0 mg for the testes, control v. stressed animals, P<0.01). The ano-genital distance in female offspring of stressed vixens was reduced (1.1 0.04 v. 0.9 0.03 cm, P<0.01). Basal ovarian oestradiol and testosterone production were decreased in cubs from prenatally stressed animals in comparison with controls (43.5 3.5 v. 32.6 3.7 pg ovary^–1 h^–1 and 0.40 0.16 v. 0.12 0.03 ng ovary^–1 h^–1, P<0.05). Prenatal stress did not affect either pituitary weights or LH content in either sex. There were no significant differences in ano-genital distance, testicular content of testosterone, or in vitro testosterone production between control and treated male cubs. In conclusion, these findings suggest that prenatal handling stress impaired the neonatal reproductive development of the female offspring, but had no marked effects on males. Sex-specific effects of prenatal handling stress on the reproductive development in foxes may be linked with the gender differences in responses of the hypothalamus–pituitary–adreno-cortical axis to stress conditions in this species.