Localization of S-100 protein in pig ovarian structures

Distribution of S-100 protein in porcine ovaries was revealed by an application of polyclonal antibodies against S-100 protein and PAP universal kit to formalin-fixed, paraffin-embedded tissues. The presence of S-100 protein was demonstrated in follicular cells of all ovarian follicles (including their atretic forms), with a decrease in intensity of the reaction parallel to an increase in follicle size. No reaction was found in oocytes, regardless of the developmental stage of the follicle. Weak expression of S-100 protein was observed in theca interna cells of mature follicles and in the youngest generation of theca-lutein cells of the corpus luteum. A distinctly positive reaction was also observed in groups of cells resembling hilus cells as well as in endothelia of arteries and some capillaries. Results are compared with data concerning the localization of S-100 protein in human and bovine ovaries. Possible relationship between the presence of S-100 protein and the level of cellular differentiation is discussed.