Intrauterine oxygen tension during the oestrous cycle in the hamster: patterns of change

Oxygen tension (pO2) within the uterine lumen of the hamster during the oestrous cycle was measured in vivo with a polarographic oxygen sensor. Mean oxygen tension underwent cyclic variation; maximum pO2 occurred during dioestrus (35.2 +/- 1.9 mmHg). Minute-to-minute alterations in pO2 also occurred; the frequency of change in pO2 was maximal during early dioestrus (94.4 +/- 8.9 peaks/hr) and minimal during pro-oestrus (31.2 +/- 5.6 peaks/hr). The amplitude of change in pO2 was maximal during late dioestrus (40.7 +/- 3.6 mmHg) and minimal during pro-oestrus (5.1 +/- 1.2 mmHg). Thus, intrauterine pO2 increases during periods of progesterone dominance and decreases under oestrogenic stimulation. Arterial and venous pO2 were 89.9 +/- 4.8 and 38.9 +/- 1.8 mmHg, respectively. Thus, mean intrauterine pO2 was consistently less than venous blood levels and varied as much as 30 mmHg during the oestrous cycle. The level of pO2 prevailing during the interval of the cycle in which insemination is permitted is intermediate to the maximum and minimum levels occurring during the oestrous cycle and is clearly sufficient to meet the metabolic requirements of spermatozoa during their passage through the uterus.