Properties of the Membranes of Rat and Rabbit Eggs

Abstract

The properties of the membranes of rat and rabbit eggs[long dash]the zona pellucida, cumulus oophorus, and in the rabbit, the so-called "albumen" layer[long dash]were studied. By histochemical technics, it was shown that all these membranes contain a large proportion of polysaccharide. The zonas are shown to be neutral or weakly acidic mucoproteins, being less acidic than the matrix of the cumulus oophorus, which is composed of hyaluronic acid and protein. Protein is demonstrable histochemically only in the zonas, but ready dissolution of the "albumen"layer and the matrix of the cumulus by pure proteinases indicates that protein forms an integral part of the structure of these layers. The term "albumen" is inappropriate, as the layer so designated has the properties of a strongly acidic mucoprotein. The effects of pH and of oxidizing and reducing agents on the integrity of the membranes were investigated, and the results are discussed in relation to theories of sperm penetration of the zona pellucida. Although the rat zona is readily disintegrated by buffers more acid than pH 5, the rabbit zona requires buffers of pH 3 or lower. Of the oxidizing and reducing agents, H2O2, with or without vit. C, is the most effective. The initial stages in the formation of the "albumen" layer were detected by histochemical methods in eggs recovered from inseminated rabbits as early as 6-8 hro after ovulation. This is discussed with reference to the suggestion that deposition of this layer provides an explanation of the short fertilizable life of the eggs in the rabbit. The inability of hyaluronidase to disperse the corona radiata of the tubal egg of the rabbit is probably due to the persistence of processes that interconnect these cells and also pass from the cells to the zona pellucida0.