Acute and chronic effects of genistein, tyrphostin and lavendustin A on steroid synthesis in luteinized human granulosa cells.
BACKGROUND
Phytoestrogens, including genistein and other inhibitors of tyrosine kinases (TKs), inhibit specific steroidogenic enzymes. This study was designed to compare the effects of genistein, with two other TK inhibitors, on steroid synthesis in human granulosa luteal (GL) cells and to identify which steroidogenic enzymes they may affect.


METHODS
GL cells, obtained from women undergoing IVF procedures, were cultured for various periods of time with and without substrates for progesterone and estradiol synthesis, in the presence or absence of the TK inhibitors.


RESULTS
The TK inhibitors significantly suppressed progesterone and estradiol synthesis in a dose-dependent manner over a 48 h culture period. Progesterone production in the presence of 10(-7) mol/l pregnenolone during a 4 h period was inhibited by both acute (4 h) and chronic (24 h) exposure of GL cells to 50 micromol/l genistein (P < 0.05) whilst no significant effects of 50 micromol/l tyrphostin A23 were observed. Genistein (4 and 24 h exposure) inhibited the production of estradiol using 10(-7) mol/l estrone as a substrate, but inhibition of estradiol synthesis using androstenedione or testosterone as substrates was only observed after a 24 h exposure. In contrast, tyrphostin acutely stimulated estradiol synthesis when androstenedione and testosterone were used as substrates (P < 0.05) but not estrone.


CONCLUSIONS
Genistein directly inhibits 3 and 17beta-hydroxysteroid dehydrogenase activity, whilst tyrphostin has an acute stimulatory effect on aromatase activity. Over a longer time (24 and/or 48 h period), both TK inhibitors suppress steroid synthesis.
Whitehead
Saffron A
SA
Department of Physiology, St George's Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK. s.whitehead@sghms.ac.uk
Cross
Julia E
JE
Burden
Clare
C
Lacey
Michael
M
D002478:Cells, Cultured; D003338:Corpus Luteum / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004958:Estradiol / Q000096:biosynthesis; D005260:Female; D019833:Genistein / Q000494:pharmacology*; D006107:Granulosa Cells / Q000187:drug effects / Q000502:physiology*; D006728:Hormones / Q000096:biosynthesis*; D006801:Humans; D010636:Phenols / Q000494:pharmacology*; D011374:Progesterone / Q000096:biosynthesis; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D013997:Time Factors; D020032:Tyrphostins / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D006728:Hormones; D010636:Phenols; D020032:Tyrphostins; C062898:lavendustin A; D011374:Progesterone; D004958:Estradiol; D019833:Genistein; D011505:Protein-Tyrosine Kinases; C060641:tyrphostin A23