Differential distribution of gangliosides in adult rat ovary during the oestrous cycle.

Gangliosides are ubiquitous membrane components in mammalian cells and are suggested to play important roles in various cell functions, such as cell-cell recognition, differentiation and transmembrane signalling. Rat ovary contained GM3, GD3 and GD1a as major gangliosides, and GM1 as a minor one. In order to study their distribution in the rat ovary and its possible changes during the oestrous cycle, frozen sections were stained with specific monoclonal antibodies against 11 ganglio-series gangliosides including those mentioned above. GM3, GM1 and GD1a were expressed in a spatio-temporally different manner during the oestrous cycle, but GD3 and other gangliosides were not immunohistochemically detected. In primary and secondary follicles, GM3, GM1 and GD1a were expressed in theca cells, but not in granulosa cells. The oocyte in primary, but not secondary, follicles was positive to the anti-GD1a antibody. In Graafian follicles, GM1 and GD1a were similarly expressed as in secondary follicles, however, the expression of GM3 spread gradually from theca cells to granulosa cells. In early Graafian follicles, only GM3 was expressed to a detectable extent from the outer part of the granulosa layer to the inner part. Shortly before ovulation, all granulosa cells and cumulus cells became positive to anti-GM3 antibody. After ovulation, differential distribution of GM3, GM1 and GD1a was also observed in luteal cells. GD1a was localized in thread-like structures, while GM3 was distributed throughout the cytoplasm, but not in the nucleus. GM1 was localized only in the plasma membrane and/or its close vicinity. Other ganglio-series gangliosides, including GD3, were not detected to an appreciable extent in the ovaries by immunohistochemistry.