자궁 무스카린수용체의 확인 및 분류

Identification and Classification of the Muscarinic Receptors in the Uterus

The muscarinic acetylcholine receptors of the dog unpregnant uterus were characterized using [3H] quinuclidinyl benzilate(QNB) as a radioligand and the binding of muscarinic receptor agonists and antagonists in the uterus was compared to that in the urinary bladder which contains almost exclusively the M2 receptors in order to determine the receptor subtypes in the uterus. [3H]QNB binding to uterus and bladder was rapid, saturable and reversible. Scatchard analysis of the saturation data gave linear plots and the Hill coefficients were close to unit, which indicated that each preparation contained a single population of specific binding sites for [3H]QNB. The KD values(l2OpM) for QNB were almost identical in both organs, whereas the Bmax value of 256fmol/mg protein in the uterus was significantly different from that of 563fmol/mg protein in the bladder. Muscarinic agonists and antagonists inhibited in a competitive manner the [3H]QNB binding to the same extent in both organs. The competition binding studies using antagonists(atropine and pirenzepine) exhibited a single binding site and this site had a low affinity for pirenzepine with the Ki value of about 330nM. However, high and low affinity binding sites were observed with carbachol, methacholine and oxotremorine. These binding studies with agonists and antagonists did not show any differences in drug affinities between uterus and bladder. These results indicate that the muscarinic receptors in the uterus are M2 receptors which have a low affinity for pirenzepine.