IDENTIFICATION OF MYOGLOBIN IN HUMAN SMOOTH-MUSCLE

Myoglobin (Mb) has been believed to be absent generally from mammalian smooth muscle tissue. Examination of human rectal, uterine, bladder, colon, small intestine, arterial, and venous smooth muscle by immunohi stochemical techniques shows that each of these tissues is immunoposit ive for both smooth muscle myosin and human Mb, Rib-specific primers w ere used for the polymerase chain reaction to generate cDNA from smoot h muscle tissues. Southern hybridization with a Mb-specific probe gave a very strong signal with the cDNA from rectum, weaker signals from s mall intestine and uterus, a faint signal from colon, and no signal fr om bladder tissue. High performance Liquid chromatography analysis cou pled with sequence determination has shown that contaminating heme-bin ding serum albumin as well as hemoglobin in extracts of smooth muscle seriously compromise any heme-based or spectrophotometric assay of Mb. Combined affinity and size exclusion chromatography, however, provide the necessary resolution. The cDNA-derived amino acid sequence of hum an smooth muscle Rib was found to be identical to that of Mb from stri ated muscle.