Expression of the receptor mRNA. Northern blot analysis. After hybridization of the human blot, a strong signal corresponding to a 2.4-kb mRNA band was detected in heart, brain, and placenta, a weaker signal was seen in liver, pancreas, and kidney. The mRNA of the receptor was hardly detected in lung and skeletal muscle. The amount of RNA on the membrane was adjusted so that β-actin hybridization is comparable in every lane.