Catecholestrogens inhibit dopamine methylation in the gonadotrops of the African catfish,Clarias gariepinus.
Isolated gonadotrops of the African catfish,Clarias gariepinus, were incubated with dopamine (DA) and/or catecholestrone and the activity of the enzyme catechol-O-methyltransferase (COMT) was determined by measuring the methylated products. From the apparent Km values for DA and catecholestrone of 0.4-1.3 μM and 17.9-25.2 μM respectively, it was concluded that catecholestrone is a better substrate for the enzyme COMT, compared to DA. Moreover, the methylation of DA is inhibited by comparatively low concentrations of catecholestrone.
Department of Experimental Zoology, Research Group for Endocrinology, University of Utrecht, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
L A
LA
Van Asselt
R J
RJ
Timmers
H J
HJ
Goos
J G
JG
Lambert
P G
PG
Van Oordt