Chicken Egg White Genes: Multihormonal Regulation in a Primary Cell Culture System

Abstract

A primary cell culture from estrogen-withdrawn chicken oviduct was developed in which the genes for the major egg white proteins, ovalbumin and conalbumin, are induced by steroid hormones. The responsiveness of the isolated cells dependes on the combination of enzymes employed to dissociate the oviduct; trypsin and pronase are essential. Administration of estradiol to cultured cells is insufficient to induce ovalbumin mRNA (mRNAov) to levels achieved in vivo. Both insulin and a 2nd ( a glucocorticoid, progestin, or androgen) are required for the induction of the ovalbumin gene by estradiol to the extent reached in vivo. Although low levels of a progestin or androgen can synergize with estradiol to the extent reached in vivo. Although low levels of a progestin or androgen can synergize with estradiol to obtain an induction of mRNAov, a physiological concentration of corticosterone (10-8 M) has been demonstrated to potentiate a large response to estradiol without causing an induction when added alone. When estradiol, corticosterone and insulin are present in the culture medium, mRNAov, increases from about 20-6500 molecules/cell by 55 h. With the same culture conditions, conalbumin mRNA increases from about 120-4300 molecules/cell by 52 h. After about 55 h, the level of egg white mRNAs decreases, and this reduction in mRNAov correlates with a diminished transcription of that gene. Apparently the induction of the ovalbumin gene requires the permissive effects of insulin and a 2nd steroid (probably a glucocorticoid in vivo) to facilitate the response to estradiol.