Morphometric Estimation of the Numbers of Granulosa Cells in Preovulatory Follicles of the Ewe

Abstract

Several lines of evidence suggest that follicular granulosa cells give rise to the large luteal cells of the corpus luteum in the sheep. To further investigate this suggestion, numbers of granulosa cells in preovulatory follicles were estimated by morphometric methods for comparison with a previous estimate of numbers of large luteal cells (9.6 ± 0.9 x 106). Preovulatory follicles from five Corriedale ewes were obtained after synchronization of the oestrous cycle with the prostaglandin analogue cloprostenol. Morphometry was undertaken using light microscopy of plastic-embedded tissue sectioned at Il-'m. Mitotic index in the membrana granulosa was 0.05 ± s.e.m. 0.05"70. Mean follicular diameter was 6.25 ± 0.25 mm and there were 7.68 ± 0.53 x 106 granulosa cells per follicle. These results demonstrate a similarity between the number of granulosa cells per follicle and the number of large luteal cells per corpus luteum and thus support the hypothesis that large luteal cells are derived from granulosa cells.