Measurement of oxytocin concentrations in plasma and ovarian extracts during the oestrous cycle of mares.

The research investigates the oxytocin levels in the blood and ovaries of mares during their ovulation cycle, concluding that their ovaries do not seem to be a source of oxytocin during this cycle.

Study Design and Methodology

• The researchers conducted their study on a total of 42 mares, with the study being split into two groups.
• The first group consisted of 9 mares from whom jugular venous blood samples were collected throughout a complete oestrous (ovulation) cycle. The purpose of this was to measure and track the levels of progesterone and oxytocin.
• The second group involved 33 mares from whom extracts of corpus luteum and follicles were obtained at different stages of their oestrous cycle. The purpose of this was to measure the concentrations of oxytocin present.
• The main tool used in this was a radioimmunoassay – a technique used to measure the concentrations of antigens in the blood by using antibodies to bind to the specific antigens. Specifically, it was used to measure the oxytocin concentrations.

Results and Findings

• The researchers found that the mean oxytocin concentration in the nine mares’ blood remained at approximately 1 picogram (pg) per milliliter (ml) throughout the entire oestrous cycle. This showed no evidence of cyclic variation in the release pattern.
• In the second group, it was discovered that all extracts of corpus luteum and follicles obtained contained oxytocin concentrations of less than 10 picograms per gram of wet weight of tissue. This showed that the ovaries are not a source of circulating oxytocin during the estrous cycle in this species.

Conclusions

• The researchers concluded that the ovaries are not a source of circulating oxytocin during the oestrous cycle in mares.
• The plasma oxytocin concentrations reported in this study are substantially lower than those found by other research groups. This discrepancy may indicate a need for further research to validate and assess these findings.