OESTROGEN ANTAGONISMS: TEMPORAL SEQUENCE OF STEROID BLOCK OF OESTRONE-INDUCED CHANGES IN VAGINAL SMEARS OF MICE

Abstract

ABSTRACT Oestrone, at a total dose of 2 μg was administered over 4 days to spayed female mice, and vaginal smears were examined twice daily for the next 6–8 days. The proportion of mice showing a positive vaginal response rises through day 2 and 3 to a plateau on days 4 and 5. Putative oestrogen antagonists, progesterone, testosterone propionate, deoxycorticosterone acetate or cortisone were given in single mg injections on day 1, 2, 3 or 4. Cortisone had no effect upon the oestrone-induced response and the effect of DCA was seen only on day 6 when it was administered on day 4. Progesterone on day 1 delays the oestrogen effect; on day 2 it inhibits the mid-portion of the time-response curve, producing a bimodal curve; and on day 3 and 4 hastens the return of the mice to the castrate condition. TP which appears to be slower in onset of action than progesterone, does not affect initial phases of the curve, but tends to hasten return to castrate condition. Oestrone alone was given with various of the days deleted from the design. The patterns of the responses did not correspond to those obtained when progesterone or testosterone were administered, implying that these steroids have direct effects and do not simply negate one or more of the oestrone injections.