The carcinogen ethionine elevates progesterone levels

Abstract

ETHIONINE is a potent carcinogen, but little is known about its mode of action. It is known that it does not react extensively with DNA¹. It may be an ubiquitous carcinogen, as it is synthesised by Escherichia coli² and several other microorganisms, so studies of its mode of action are important. We reported recently a novel effect of ethionine in the immature chick³. The oviducts of chicks previously stimulated with oestrogen behaved after the administration of ethionine as if they had received a second stimulation with oestrogen or progestin^4–6. The egg white proteins, ovalbumin and conalbumin were synthesised and distinct morphological changes, characteristic of stimulation by oestrogen or progestin appeared. It was thus not clear whether ethionine (or its metabolic product) was affecting steroid hormone receptors⁷ directly, or interferring in some way with steroid hormone metabolism to produce elevated levels of endogenous oestrogen or progestin. We report here that ethionine or its sulphoxide are unique in inducing in the chick oviduct the effects cited above; analogues were inactive. We also report that the administration of ethionine elevates serum progesterone levels over 10-fold, to a concentration which may be sufficient to account for the profound changes in the immature oviduct.