Changes in the metabolic pattern of estrogens as a function of age in cultured myometrial cells: synthesis of a lipoidal derivative of estradiol.

The effect of ageing on estradiol (E2) metabolism has been studied systematically in cultured ovine myometrial cells from the 2nd to the 25th subculture. Cell monolayers were incubated for various amounts of time with [3H]E2, and metabolites isolated from cells or medium by thin-layer chromatography (TLC). The main metabolites identified were estrone (E1), estriol (E3), 16-epi-E3 and a lipoidal derivative of E2 (LE2). The latter had an Rf of 0.90 and was recognized by its comigration with fatty acid on TLC and the release of E2 after alkaline hydrolysis. In contrast to the other metabolites, LE2 was found only in cells and was never secreted in the medium. In "young" cells (2nd subculture) the main metabolite was E1 which represented 16.3% of the total radioactivity after 2 h of incubation and 33% after 8 h both in cells and medium. LE2 appeared very slowly and represented only 13% after 8 h of incubation. In contrast in "old" cells (i.e. 10th subculture) LE2 had become the most abundant metabolite representing as much as 25% of the total cellular radioactivity. This change from one metabolic pattern to the other was progressive and associated with a decrease in 17 beta-hydroxysteroid dehydrogenase (SDH) activity. LE2 became prevalent relative to E1 around the 5th subculture. In conclusion, ageing in cultured myometrial cells is accompanied by a qualitative change in E2 metabolism, switching from E1 formation (an inactivation mechanism) to LE2 biosynthesis (a storage mechanism).