Human Reproduction, Vol 12, 95-100, Copyright © 1997 by Oxford University Press
RH Hunter, C Grondahl, T Greve and M Schmidt
In order to establish appropriate culture temperatures for in-vitro
maturation of pig ovarian oocytes, large Graafian follicles (7-10 mm
diameter) were sensed by infra-red technology during the latter part of a
spontaneous oestrous cycle. Temperatures were measured under systemic
anaesthesia almost instantaneously upon revealing the ovaries at mid-
ventral laparotomy. Temperature differentials were observed within all 16
ovaries sensed in 14 animals. Ovaries were always cooler than deep rectal
temperatures (mean rectal temperature was 38.0 +/- 0.4 degrees C; range
37.5-38.6 degrees C) and mature follicles always cooler than ovarian stroma
(35.6 +/- 0.3 degrees C versus 37.3 +/- 0.2 degrees C respectively; P <
0.01). Such follicles were frequently 1.5-1.8 degrees C cooler than the
adjacent stroma, the mean being 1.7 +/- 0.4 degrees C. Small Graafian
follicles (< 5-6 mm diameter) and recent ovulations did not show this
differential. The control experiment of excising an ovary, deep freezing it
in liquid nitrogen, and then restoring it to the body cavity before further
sensing indicated that intra-ovarian temperature gradients depended on the
activity of living tissues and/or a functional blood supply. Furthermore,
calculation of anticipated rates of cooling for exposed Graafian follicles
strongly suggested that artefacts could not have been solely responsible
for the observed temperatures. Endothermic reactions within mature
follicles were thus brought into focus. It is concluded that follicular
temperatures may influence the meiotic progression and cytoplasmic
maturation of oocytes and act to regulate enzymatic activity in the
biosynthetic pathways for steroid and/or peptide hormones.
ARTICLES
Graafian follicles are cooler than neighbouring ovarian tissues and deep rectal temperatures
Department of Clinical Studies--Reproduction, Royal Veterinary and Agricultural University, Frederiksberg C, Copenhagen, Denmark.
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