New functional zonation in the ovary as shown by immunohistochemistry of luteinizing hormone receptor.

Monoclonal anti-LH receptor antibodies were used to study receptor distribution in the various structures of porcine ovary. Primordial and primary follicles were not labeled. Immunoreactivity appeared on the thecal cells of secondary follicles of approximately 100-200 microns in diameter. In large antral follicles and preovulatory follicles granulosa cells were also labeled, whereas two zones were observed in the theca interna. The region close to the lamina basalis (approximately 1/3 of the thecal cells) appeared devoid of LH receptors, whereas a strong labeling was observed on the most external region. Thecal cells were also labeled in atretic follicles. There was no labeling of the oocyte. In cyclic corpora lutea only the most external cells, probably of thecal origin, were stained. The most abundant cells, of granulosa origin, were not labeled. In the interstitium few cells were immunolabeled; they proceeded either from remnants of atretic follicles or existed as groups of isolated cells. Thus both the theca interna of preovulatory follicles and the corpus luteum are heterogenous structures composed of two zones of which only one is directly responsive to LH. No LH immunoactivity could be detected in nontarget organs (liver, lung, thyroid gland, small intestine, fallopian tube, and uterus).