Biotransformation of estradiol in the human keratinocyte cell line HaCaT: metabolism kinetics and the inhibitory effect of ethanol.
OBJECTIVE
The aim of our study was to investigate the kinetics of beta-estradiol (E2) metabolism in the human keratinocyte cell line HaCaT and to estimate the effect of the potential inhibitor ethanol on the biotransformation reaction.


METHODS
The formation rates of estrone (E1) in dependence on substrate concentrations were determined in HaCaT cells using tritium labelled E2. Experiments were conducted with and without addition of dehydroepiandrosterone (DHEA) and ethanol. Possible toxic effects on the cells due to ethanol were investigated by cytotoxicity tests.


RESULTS
The metabolism of E2 in HaCaT cells exhibited Michaelis-Menten kinetics with Km and Vmax values of 3.5 microM and 216 pmol x mg(-1) protein x h(-1), respectively. The reaction was inhibited by DHEA and ethanol. The alcohol showed a reversible competitive inhibition mechanism for concentrations of 4 to 8% (v/v). Lower ethanol concentrations had no effect, whereas levels > or =10% significantly decreased cell viability leading to a different inhibition mechanism.


CONCLUSIONS
The HaCaT cell line seems to be a suitable model for studying enzyme kinetics equivalent to the human skin. The concentration dependent inhibitory effect of ethanol observed in this cell line may be relevant for the transdermal E2 application in patients.
Altenburger
R
R
Department of Pharmaceutics and Biopharmacy, Philipps-University, Marburg, Germany.
Kissel
T
T
D001711:Biotransformation; D002460:Cell Line; D003687:Dehydroepiandrosterone / Q000494:pharmacology; D004958:Estradiol / Q000493:pharmacokinetics*; D004965:Estrogen Antagonists / Q000633:toxicity*; D000431:Ethanol / Q000633:toxicity*; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism*
D004965:Estrogen Antagonists; D000431:Ethanol; D003687:Dehydroepiandrosterone; D004958:Estradiol