Long-latency growth-promoting activity of EGF when administered to mice at the neonatal stage

The effect of biosynthetic human epidermal growth factor (Bh-EGF) as well as mouse EGF on postnatal development of mice of ICR strain was examined. Daily administration of Bh-EGF (0.01, 0.1, and 1.0 microgram X g body wt-1 X day-1) for 30 consecutive days postpartum caused a clearly dose-dependent increase in their body weight. Furthermore, in addition to the well-known premature eyelid opening and early tooth eruption, we have also observed precocious opening of the vagina among treated females. As far as the accelerated growth rate as reflected in their body weight gain was concerned, daily administration for only five consecutive days postpartum was just as effective as the above noted 30 consecutive daily injections. As to the precocious vaginal opening, however, the susceptible 5-day-period was found to be 14-18 days after the parturition. Some of those treated females also entered the estrous cycle precociously, a few days after the precocious opening of their vagina. The microscopic examination of various organs from treated males and females revealed no apparent pathological changes. As far as the above noted effects of EGF were concerned, Bh-EGF, which is xenogenic to mice, was as potent as mouse EGF.