An investigation of an estrogen-binding component in the liver and plasma of brook char, Salvelinus fontinalis

Abstract

1. 1. Estrogen-binding activity was investigated in liver nuclear and cytosolic preparations of sexually mature female brook char, Salvelinus fontinalis. Nuclear salt extracts of estrogen-injected fish were found to contain high affinity binding sites ( K d = 1.6nM, capacity = 2.8 fM μg DNA). 2. 2. Low levels of high-affinity specific binding activity were found in the cytosol of both injected and untreated fish ( K d = 7.5 nM, capacity = 16.1 fM/mg protein). 3. 3. Binding sites in both preparations were specific for estrogens with no significant competition by 5α-dihydrotestosterone, progesterone, or cortisone. 4. 4. A plasma-binder was found to have distinctive differences with regard to structural specificity compared to the estrogen-binding component in liver. It was found to have no affinity for diethylstilbestrol while having some affinity for both 5α-dihydrotestosterone and progesterone. 5. 5. The brook char liver estrogen-binding component was observed to have characteristics in common with estrogen receptors found in other vertebrates.