THE RESPONSE OF INBRED MICE TO OESTROGENS

Abstract

SUMMARY The vaginal response of two inbred lines of mice (C57 and CBA), and their reciprocal crosses, to oestrone and oestradiol-3:17β has been studied, with the subcutaneous and intravaginal routes of administration. In all cases the variability of the response of F1 hybrids was approximately 25% of the variability of the inbred lines. In the intravaginal tests the median effective dose (m.e.d.) was the same for both inbred lines, while the m.e.d. for the F1 hybrids was less. In the subcutaneous tests the C57 line has a lower m.e.d. than the CBA line, while the m.e.d. of the F1 hybrids was lower than both the inbred lines. This phenomenon is an example of heterosis, and the findings have been discussed in relation to bioassay and experimental study of oestrogens, and to mammary carcinoma in the mouse.