Serum protein of 135-kDa molecular weight--a molecular signal for cardiac hypertrophy.

A serum protein, similar to the 135-kDa protein which appears during experimentally induced cardiac hypertrophy in rats, was identified in human serum by Western blot analysis using anti-rat 135-kDa protein antibody. The rat protein antibody gave a very strong positive signal when reacted with sera obtained from cardiac patients, suggesting an induced level of this protein in patients' sera when compared to normal sera from healthy individuals. Multiple injections of polyclonal anti-rat 135-kDa protein antibody to aorta-constricted animals completely inhibited the development of cardiac hypertrophy, suggesting that this protein could be hypertrophy specific. This was further substantiated by the decrease in the expression of a molecular marker such as the beta myosin heavy chain gene in aorta-constricted but antibody-injected animals. Further, the presence of high levels of this protein in first- and third-day neonatal animals is also suggestive of the hypertrophy-specific nature of this protein as the heart is subjected to high pressure overload immediately after birth.