Plasma Gonadotropins, Prolactin and Progesterone at the Time of Implantation in the Mouse: Effects of Hypoxia and Restricted Dietary Intake

To assess the effects of hypoxia and other noxious stimuli on the secretion of gonadotropins and prolactin at the time of implantation, blood was collected at 6 h intervals between Days 1-3 of pregnancy from mice assigned to either 1) a control group or groups. 2) exposed to 8% 0 2 (hypoxia). 3) pair fed to the 8% 0 2 group or 4) fasted. In the control mice, plasma LH reas gradually to a peak at 0600 h on Day 3, whereas FSH levels were low and failed to exhibit any temporal pattern. Plasma LH and prolactin were significantly suppressed (P>0.05) within 6 h after the onset of the various treatments. In a second study, in which mice were sampled once daily at 1200 h, the plasma progesterone concentration in the control group increased from Day 1 to 4 of gestation. However, the levels of progesterone in plasma of mice which were fasted or exposed to hypoxia were significantly reduced (P>0.05) on the day of implantation. When gonadal steroids were administered to mice exposed to 8% O 2 , the contragestational effects of hypoxia were ameliorated. In conjunction wit the findings of previous investigations (Rattner et al., 1976, 1978), it is concluded that the reproductive dysfunction induced by hypoxia may be attributed to inadequate dietary, metabolic, luteotropic and steroidal maintenance of gestation.