Quantitative histochemical measurement of pyruvate and lactate in mouse oviduct during the estrous cycle

Pyruvate and lactate are important energy sources for preimplantation embryos cultured in vitro. The purpose of this study was to determine in vivo levels of these substances in mouse oviductal tissues throughout the estrous cycle. Quantitative histochemical assays were developed to analyze these metabolites in submicrogram samples of freeze-dried ampullar and isthmic oviduct. The potential for other alpha-keto acids to interfere with the pyruvate assay was assessed and found to be minimal with this procedure. The importance of the collection method in maintaining in vivo metabolite levels was demonstrated by the marked changes observed with extended anoxia or pentobarbital anesthesia. Pyruvate levels at 3 hr postovulation (2.6 mmol X kg-1 dry weight) were higher than 12 hr before ovulation or 12 to 72 hr after ovulation (1.6 to 2.2 mol X kg-1) in both ampulla and isthmus. Lactate levels were significantly increased at 12 to 24 hr in the isthmus (28 mmol X kg-1) compared to other times during the cycle (9-19 mmol X kg-1). The observed levels of these metabolites may reflect changes in oviductal metabolism, induced by the hormone pattern of the estrous cycle, that promote the availability of needed energy substrates for the early embryo.