Micro-disc electrophoresis of soluble proteins in rabbit blastocysts.

Soluble proteins were studied in the developing rabbit blastocyst by using a micro-disc electrophoresis technique. The tissues of the blastocyst (in later stages separated into the embryoblastic and trophoblastic parts) were analysed, and their protein patterns were compared with those of uterine secretion and blastocyst fluid. A protein pattern with more than 20 protein fractions was found in the tissues of the blastocysts. This protein pattern was quite different from those previously reported in uterine secretion or blastocyst fluid. After cleavage and during early phases of development of blastocysts the protein pattern was changing; from the 5th day p.c. it became fairly homogeneous. The protein patterns of the embryonic and trophoblastic parts of the blastocyst tissues were rather similar. The origin of the proteins in the blastocyst fluid is discussed.