AHTN and HHCB show weak estrogenic - but no uterotrophic activity

The ubiquitous presence of the polycyclic musks AHTN (6-acetyl-1,1,2,4,4,7- hexamethyltetraline) and HHCB (1,2,4,6,7,8-hexahydro-4,6,6,7,-hexamethylcyc lopenta-gamma-2-benzopyreen) in surface waters and their identification in human milk fat together with their polycyclic nature, which makes them pote ntial candidates for interference with estrogen receptors, prompted us to a ssess these compounds for their potential estrogenic effects. We therefore investigated the effects of AHTN and HHCB in ER alpha- and ER beta-dependen t gene transcription assays with Human Embryonal Kidney 293 (HEK293) cells, which have proven to be very suitable to estimate the estrogenic activity of compounds with low binding activity (Kuiper, G.G., Lemmen, J.G., Carlsso n, B., Corton, J.C., Safe, S.H., Van der Saag, P.T., Van der Burg, B., Gust afsson, J.A., 1998. Interaction of estrogenic chemicals and phytoestrogens with estrogen receptor beta. Endocrinology 139, 4252-4264). Both AHTN and H HCB were found to induce a slight but dose-dependent stimulation of transcr iptional activity in the transiently ER alpha transfected HEK293 cells. Thi s weak estrogenic response was not observed in the ER beta transiently tran sfected cells. However, these cells were less responsive to estradiol than the ER alpha transfected HEK293 cells. Also, no significant increase in tra nscriptional activity was observed in HEK293 cell lines, permanently expres sing the same estrogen-responsive reporter gene construct and either ER alp ha or ER beta. In the classical uterine weight assay performed in juvenile Balb/c mice, no uterotrophic activity of AHTN and HHCB was noted at relativ ely high dietary exposure levels up to 50 and 300 ppm, respectively, at whi ch levels an increase in liver weight was evident. Also the vitellogenin pr oduction by carp hepatocytes, a sensitive marker of estrogenic activity, wa s not affected by these two fragrance materials (Smeets, J.M.W., Rouhani Ra nkouhi, T., Nichols, K.M., Komen, H., Kaminsky, N.E., Giesy, J.P., Van den Berg, M., 1999. In vitro vitellogenin production by carp (Cyprimus carpio) hepatocytes as a screening method for determining (anti-) estrogenic activi ty of xenobiotics. Toxicol. Appl. Pharmacol., 157, 68-76). Therefore it is concluded that these compounds have very weak estrogenic potency, too weak to induce estrogenic effects in wildlife species or humans at the current l evels of exposure. These results give further support to the promiscuity of estrogen receptors. (C) 1999 Elsevier Science Ireland Ltd. All rights rese rved.