Sequential steroid hormone treatment antagonizes the action of estrogen in chick oviduct.

Abstract

Abstract We have studied the effects of the sequential administration of hormones to estrogen-withdrawn chicks on oviducal estrogen receptor levels, ovalbumin mRNA accumulation and oviduct wet weight gain. Chicks were primed with estrogen 8–18 h before the administration of progesterone, dihydrotestosterone, testosterone or estrogen. The second hormone treatment did not affect oviduct wet weight gain or the levels of cytosolic estrogen receptor. The rate of ovalbumin mRNA accumulation decreased from 2–6 h after all second hormone treatments except testosterone. By 12 h following injection of the second hormone, ovalbumin mRNA levels had recovered to that found in the control chicks. The levels of salt extractable nuclear estrogen receptor were affected by all the second hormone treatments. Following progesterone, dihydrotestosterone or low doses of estrogen (0.5 mg) nuclear receptor levels decreased in parallel with ovalbumin mRNA accumulation. However following testosterone, and intermediate or high doses of estrogen (1–2 mg), changes in the nuclear estrogen receptor levels did not correlate with changes in ovalbumin mRNA accumulation. Thus, the levels of the salt-extractable nuclear estrogen receptor may not always measure the amount of receptor actively involved in the regulation of gene expression in the chick oviduct. These studies emphasize the importance of correlating biological phenomena with receptor data in order to determine whether the method employed to measure receptor levels is appropriate in the systems under study.