Identification of hepatic, non-monoamine, dihydroergocryptine binding sites with significant gender differences

High affinity [3H] dihydroergocryptine binding sites different from alpha1/alpha2-adreno, dopamine or serotonin receptors were detected in a crude membrane fraction from hamster liver by radioligand binding filtration assay. The binding was saturable and reversible, as well as time and protein dependent. Scatchard analysis revealed a single population of binding sites with Kd 3.8 +/- 0.9 nM and Bmax = 675 +/- 130 pmol/g tissue (mean +/- S.E.M., n=6) in the male hamster crude liver membrane fraction. In the female liver membranes the Kd value was 4.4 + 1.2 nM and Bmax = 1025 +/- 190 pmol/g tissue (mean + S.E.M., n = 6). Differences between males and females in Bmax values were significant (P < 0.01). The most potent inhibitors of [3H] dihydroergocryptine binding were bromocriptine > ergotamine > dihydroergocryptine > dihydroergocristine > alpha ergocristine > dihidroergotamine > ergocornine > ergocristine > nicardipine > (+) butaclamol > PK 11195 > nitrendipine > domperidone > (-)butaclamol (in order of decreasing affinity). The described type of dihydroergocryptine binding sites was not detected in hamster brain, kidney, spleen or lungs. Obtained data support the concept that some ergot-derivatives may induce metabolic effects in the liver through peripheral mechanisms other than those, mediated by alpha-adrenoreceptors.