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

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, gonada l testosterone and oestradiol content and in vitro production, and pituitar y 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 incu bates and homogenates were analysed for testosterone and oestradiol by radi oimmunoassay and the pituitary homogenates for LH by immunofluorometric ass ay. 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 s tress resulted in a significant reduction of morphometric and hormonal meas ures of the reproductive system in neonatal blue foxes, with more drastic e ffects in female cubs. Gonadal weights were lower in cubs of both sexes fro m 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 stresse d animals in comparison with controls (43.5 +/- 3.5 v. 32.6 +/- 3.7 pg ovar y(-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 e ither sex. There were no significant differences in ano-genital distance, t esticular content of testosterone, or in vitro testosterone production betw een control and treated male cubs. In conclusion, these findings suggest th at prenatal handling stress impaired the neonatal reproductive development of the female offspring, but had no marked effects on males. Sex-specific e ffects of prenatal handling stress on the reproductive development in foxes may be linked with the gender differences in responses of the hypothalamus -pituitary-adrenocortical axis to stress conditions in this species.