Pre-ovulatory Graafian follicles are cooler than neighbouring stroma in pig ovaries

Using an infra-red camera, domestic pig ovaries were thermo-imaged almost i nstantaneously at laparotomy or within a closed abdomen by endoscopy: Recta l and jugular vein temperatures were recorded using thermo-probes. Graafian follicles (7-10 mm diameter) were cooler than ovarian stroma in all experi mental models examined, and both compartments mere cooler than rectal and j ugular temperatures. The mean difference between follicles and stroma in 73 observations was 1.3 +/- 0.1 degrees C. When thermo-imaged under the fimbr iated extremity of the Fallopian tube, follicles and stroma could still be distinguished. Follicles cooled slightly more rapidly than adjoining stroma during the first 10 s of a 60 s recording interval, after which curves for the two tissues remained parallel. Arresting ovarian blood supply for 5 mi n had a negligible influence on the temperature differentials. Endoscopy in three models recorded mean differentials between follicles and stroma of 0 .6 +/- 0.1 degrees C to 1.1 +/- 0.1 degrees C. It is concluded that tempera ture gradients do exist in the ovarian tissues of mature animals, and that these are generated at least in part as a consequence of endothermic reacti ons within Graafian follicles.