Evaluation of enzyme tests in the diagnosis of heart disease∗

Glutathione transferase in the urine: a marker for post-transplant tubular lesions

Basic glutathione transferase released from the proximal tubular epithelium in the kidney was monitored in the urine of 69 recipients of renal allografts. The enzyme was isolated from human liver and the urinary analysis performed with radioimmunoassay. Patients receiving cyclosporine A without toxicity or rejection did not excrete this enzyme in their urine; whereas the urine of patients with cyclosporine A-induced nephrotoxicity contained significant amounts of the transferase (P less than 0.001). Patients with allograft rejection also showed increased urinary concentrations of the basic glutathione transferase, but had significantly lower values than patients with cyclosporine induced nephrotoxicity (P less than 0.001). During aminoglycoside and co-trimoxazole treatment, the urinary concentration of this transferase also increased. Patients with renal infarction showed a sudden increase in urinary transferase to very high levels. The results indicate that quantitative analysis of the basic glutathione transferase in urine is useful for monitoring renal tubular lesions present in various complications following transplantation, such as cyclosporine and antibiotic induced nephrotoxicity and renal infarction.

Creatine kinase and myoglobin determination in myocardial infarction (determination of infant size)

In order to evaluate the diagnostic and prognostic importance of serum myoglobin (Mb) determination during acute myocardial infarction (AMI) we determined the time of first rise of both CK and Mb, that is the time in hours between the onset of pain and the last normal myoglobin and enzyme determination (TFR for Mb = 2.2 +/- 1.5 h; TFR for CK = 4.0 +/- 2.5 h). We also attempted to evaluate infarct size by mathematical analysis of the serum concentrations of Mb. The average percentage difference between the infarct size calculated from the CK concentrations and Mb concentrations was 35.8 +/- 35.2%. The results show that the determination of serum myoglobin is a useful and sensitive test for the early diagnosis of AML. On the other hand, the serum myoglobin cannot be utilized to evaluate infarct size. The main limitation in the determination of infarct size from the serum Mb concentrations lies in the extreme variability of the disappearance rate (Kd), mainly resulting from the renal elimination of the substance.

Quantitative assessment of the extent of myocardial infarction in the conscious dog by means of analysis of serial changes in serum creatine phosphokinase activity

This study was designed to develop a method for quantitative assessment of infarct size in the conscious animal based on serial changes of serum creatine phosphokinase (CPK) activity. From 11 experiments in which myocardial CPK was injected intravenously in conscious dogs, the average CPK distribution space and average CPK fractional disappearance rate from serum were found to be 11.4% of body weight and 0.48% min respectively. In other experiments, myocardial infarction was produced in 22 conscious dogs by constriction of a left coronary artery snare and serum CPK activity was determined at frequent intervals for 24 hr. Since myocardial CPK depletion reflects infarct size, infarct size was determined directly by analysis of myocardial CPK content in the same animals 24 hr after coronary artery occlusion. CPK released from the infarct was determined from observed changes in serum CPK activity analyzed according to a model taking into account the fraction of CPK released from an infarct and the rates of appearance and disappearance of CPK activity from serum. Infarct size was calculated on the basis of observed changes in serum CPK and compared to infarct size determined directly by analysis of myocardial CPK depletion. Agreement was close and results from all experiments fit the equation: [infarct size (g) determined from serum CPK] = 1.13 x [infarct size (g) determined from myocardial CPK] - 1.3, r = 0.96, n = 22. The method described is useful for accurate assessment of infarct size in the conscious animal and for detection of modification of infarct size produced by pharmacologic interventions.