FACTORS INVOLVED IN THE FERTILIZATION OF MOUSE EGGS <i>IN VITRO</i>

Abstract

Summary. Mouse eggs recovered from follicles before ovulation and from oviducts at various times after ovulation were inseminated in vitro with epididymal spermatozoa in the presence of heated bovine follicular fluid and examined 8 hr after incubation. The eggs recovered 4 hr before ovulation could be penetrated by spermatozoa and underwent fertilization, but their zona reaction to block further sperm entry was weaker than in eggs recovered 2 hr before, or at various times after, ovulation. The failure of extrusion of polar bodies was observed in a high proportion of ovarian eggs undergoing fertilization. The fertile life of mouse eggs lasted about 10 to 12 hr after ovulation and the failure of transformation of sperm heads as well as the activation of eggs was observed in the aged eggs. Sperm penetration and fertilization in vitro of tubal eggs could be influenced by spermatozoa or eggs from different strains of mice. The presence of epididymal extract appeared to inhibit sperm penetration. The concentration of spermatozoa, the concentration of calcium ions and the pH value of the medium during incubation could all affect the capacitation of mouse spermatozoa and the penetration of mouse eggs in vitro.