Measurement of Serum Enzyme Turnover Rates

SUMMARY

The half-lives of a number of serum enzymes were derived in a patient with acute muscle necrosis. A unit of plasma was withdrawn from the patient during the height of his illness and was infused back into his circulation when he had recovered. The disappearance rates of six commonly measured enzymes were calculated. The enzymes appeared to follow biphasic disappearance rates—a rapid early rate, probably due to dilution into extravascular compartments combined with urinary excretion of smaller enzymes, followed by a later, slow rate of disappearance that did not depend upon molecular weight.

The patient appeared to be suffering from acute alcoholic myopathy as manifested by severe generalized weakness, muscle tenderness, and myoglobinuria. The laboratory diagnosis of myoglobinuria is discussed, and evidence is presented that in this case hemoglobin was also present in the urine.

The case was unique in that the acute skeletal muscle necrosis was accompanied by an acute myocardial infarction.