PURPOSE: The infusion of a bacterial solution into the uterus of rats raises the progesterone (P4) concentration in serum and extends diestrus. To understand the origin of the P4, we investigated the change in the P4 concentration of seven groups of rats for 5 days after the infusion of a bacterial solution. METHODS: The rats were divided into 7 treatment groups as follows: OvxBac, AdxBac, Ovx, Adx, LapBac, Lap, and Cont. In OvxBac, rats received both ovariectomy and bacterial inoculation into their uterus. In AdxBac, rats received both adrenalectomy and bacterial inoculation into their uterus. In Ovx, rats received only ovariectomy. In Adx, rats received only adrenalectomy. In LapBac, rats received only bacterial inoculation into their uterus. In Lap, rats received only laparotomy. In Cont, rats did not receive any treatment and acted as controls. RESULTS: The P4 concentration in all treatment groups was higher than in Cont on day 1 (the day following operation) and day 2. In Lap and LapBac, the P4 concentration was high on day 1 (>30 ng/mL) and maintained that value until day 2. In Adx and AdxBac, the P4 concentration was average on day 1 (approximately 25 ng/mL) and increased on day 2 to a value close to that of LapBac and Lap. In OvxBac, although the P4 concentration increased slightly on day 1 and day 2, it reached 22.5 ± 7.5 ng/mL on day 4. In AdxBac and LapBac, the P4 concentration on day 4 tended to be high. CONCLUSION: These results suggest that P4 is initially secreted from the ovaries and the adrenals in response to the surgical stress of laparotomy, and is later secreted from the adrenals due to the inflammatory reaction of the uterus.
