MYOGLOBIN TURNOVER - INFLUENCE OF RENAL AND EXTRA-RENAL FACTORS

Abstract

The serum level of myoglobin [MB], a LMW [low molecular weight] constituent of human striated and myocardial muscle, was studied in various clinical situations to obtain information about factors influencing Mb turnover. The Mb level was significantly correlated to different variations of GFR [glomerular filtration rate], such as serum .beta.2-microglobulin, serum creatinine and 51Cr-EDTA clearance. Following a successful renal transplantation rapid decrease in serum Mb paralleled increases in GFR. In patients with advanced long-standing uremia, comparatively small elevations of serum Mb were seen when correlated to the degree of GFR reduction, demonstrating an influence of extrarenal factors on the Mb levels. The importance of extrarenal factors on the actual serum level of LMW proteins was also illustrated by serial studies on SLE [systemic lupus erythematosus] patients receiving corticosteroid therapy. In these patients, elevations of serum Mb levels were found, but serum .beta.2-microglobulin levels gradually decreased during therapy. Calculations based on curves of serum disappearance of Mb in patients with acute myocardial infarction indicated that only about 0.3 mg of Mb/day was released from the muscle pool during normal conditions, which suggests that Mb catabolism mainly occurred within the muscle tissue.