CHARACTERIZATION OF MUSCARINIC CHOLINERGIC RECEPTORS IN HUMAN OVARIES, OVARIAN-TUMORS AND TUMOR-CELL LINES

Using [H-3]quinuclidinyl benzilate (QNB) as radioligand, muscarinic cholinergic receptor sites in isolated plasma membrane fractions from human ovarian tumours, cultured tumour cells, and normal ovarian tissue were characterised. QNB binding to all preparations, except from poorly differentiated tumour, was specific, saturable, and of high affinity. In contrast to normal ovaries, benign tumours, well differentiated adenocarcinoma and OVCAR-3 cells, the poorly differentiated adenocarcinoma and SKOV-3 cells completely lacked specific QNB binding. The muscarinic receptor densities and the K(d) values in preparation from ovaries, receptor-positive tumours and OVCAR-3 cells were similar. QNB binding was strongly inhibited by the classical muscarinic receptor antagonist atropine, but poorly by the agonist carbachol. In contrast to atropine, inhibition by pirenzepine and AF-DX 116 was relatively low. These data suggest that muscarinic receptors in ovaries and ovarian tumours are of m3 type.