Expression of muscarinic receptor genes in the human coronary artery.

The authors investigated the role of muscarinic receptors in functional control of coronary arteries affected by intimal thickening due to arteriosclerosis. They first examined the genetic subtypes of muscarinic receptors expressed in human coronary arteries. Twelve samples of human coronary artery, obtained by autopsy from eight subjects, were examined for the expression of four genetic subtypes of muscarinic receptor, m1 to m4, by reverse transcription and polymerase chain reaction (RT-PCR). Two subtypes, m2 and m3, were found to be expressed in the coronary artery. The m2 gene was expressed in seven of the 12 vessels, and m3 in eight of the 12. Expression of both m2 and m3 genes was observed in five of the 12 vessels. Neither the m1 nor m4 was expressed in these samples. These results indicate that the m2 and m3 genes are mainly expressed in the coronary arteries and suggest that these patterns of expression are differentially controlled to induce the diversity of contraction/relaxation reactions induced in the coronary arteries by acetylcholine.