Total Creatine Kinase and Isoenzyme Fractions in Chronic Dialysis Patients

We measured total serum creatine kinase (CK) and serum creatine kinase MB fraction (CK-MB) in 53 patients on continuous ambulatory peritoneal dialysis (CAPD) and 52 patients on maintenance hemodialysis (HD), using Scalva UV methodology for CK and electrophoresis for CK-MB. Seven of the 53 CAPD patients (13%) had an elevated total CK, and only one of these 7 patients had an elevated CK-MB > 5%. In contrast 22 HD patients (42%) had increased total CK values, and 6 of these 22 HD patients (27%) showed elevated CK-MB isoenzyme > 5%. For each sex, blacks had higher mean CK values than whites. Twenty-one out of the 43 HD patients who received intramuscular injections had elevated total CK values and 6 of these 21 patients had elevated CK-MB isoenzyme independent of the timing of injection. The increased frequency of higher total CK values in HD patients appears to be related to race and androgen administration. The modest elevations in CK-MB fraction (5 to 8%) in these patients require careful interpretation.

Elevated levels of plasma lipofuscins in patients with chronic renal failure

The fluorescence excitation and emission spectra observed in plasma from patients with chronic renal failure were reproduced by the generation of soluble lipofuscins in normal plasma samples by incubation with mixtures of L-dopa, dopamine, L-norepinephrine, L-epinephrine, 3-hydroxy-DL-kynurenine and 3-hydroxy-anthranilic acid for 24 h at 37 degrees C. Relative fluorescence intensity measurements consistently showed elevated plasma levels of the soluble lipofuscins in chronic renal failure: the means (n = 27) were 73.9 +/- 33.4 (SD) and 71.1 +/- 14.8 at emissions 413 nm and 445 nm respectively, in contrast to those of normal plasma samples (n = 11), 18.2 +/- 5.3 and 23.1 +/- 5.6. The maximum or shoulder at approximately 413 nm represents soluble lipofuscin that can be generated from 3-hydroxyanthranilic acid and the maximum or shoulder at approximately 445 nm represents soluble lipofuscins derived from the precursors listed above and probably from other related precursors. Gravimetric measurements also showed elevated levels of melanins in the plasma samples of patients with chronic renal failure: 2.72 +/- 0.38 mg/ml (n = 16), as compared to normal values: 1.70 +/- 0.10 mg/ml (n = 6). In individual patients haemodialysis reduced the fluorescence intensities to a range of 65-99% and the melanin levels to a range of 86-99% of the pre-dialysis values.

Creatine kinase

Creatine kinase is present in significant concentrations in skeletal muscle and cardiac muscle and to a lesser extent in gastrointestinal tract and brain tissue. The enzyme has been purified from a variety of tissues and an examination of its kinetic and physical properties reveal that the enzyme consists of two subunits and can exist as three isoenzymes containing essential cysteine residues. These properties are important in understanding its stability, the assay conditions, and the techniques used to identify the different isoenzymes. The relationship between the properties and the determination of the enzyme in biological fluids will be a main thrust of the review. Creatine kinase activity in serum rises rapidly in conditions such as acute myocardial infarction and trauma to skeletal muscle. However, the interpretation of such increases is dependent upon a sound knowledge of the factors which influence both the total and isoenzyme activities. The nature of these factors will be discussed in detail.

Evaluation of the new Beckman electrophoretic method for CK-MB: comparison with ion exchange chromatography and investigation of a reference outpatient population

We evaluated the performance of a CK isoenzyme kit utilizing agarose electrophoresis with fluorescence scanning of an overlay paper rather than the gel. We compared this method to ion exchange chromatography with mini-columns of DEAE Sephadex using samples from hospitalized patients and from a reference population of ambulatory outpatients with common, chronic medical conditions. The detection limit, precision and linearity of the electrophoretic method were acceptable, but the method overestimated CK-MB, requiring a different reference range for clinical application. There were inter-racial differences within the reference population for total CK and for the percent of CK-MB using either method. We discuss the significance of our findings with respect to clinical decision limits for CK-MB.

Plasma protein binding in uremia: extraction and characterization of an inhibitor

The impairment of binding drugs and other substances to serum albumin in patients with uremia can be restored to normal or near normal levels by adsorption with charcoal or synthetic polymers at pH 3. We used a nonionic poly-styrene-divinylbenzene copolymer to treat uremic plasma at pH 3. We observed a marked improvement of binding. Subsequent elution of this resin with ethanol produced a substance that, when dried and recombined with normal plasma, caused dose-dependent impairment of phenytoin and tryptophan binding. Restoration of normal binding affinity occurred after retreatment of this abnormalized plasma with resin at pH 3. Plasma and pleural fluid exudate from patients with uremia yielded, after extraction by the above technique, and inhibitor(s) of phenytoin binding in amounts averaging five times that extracted from equal volumes of normal plasma. This inhibitor (IX) is water soluble, heat stable, and dialyzable across cellophane membranes. Unlike fatty acids, which can also interfere with binding, IX partitions primarily in the water phase in solvent partition studies but undergoes a sharp transition in th pH 4 to 5 range, suggesting the presence of carboxyl group. These findings lend further support to the hypothesis that a retained ligand(s) is responsible for impaired plasma binding associated with uremia and suggests a role for organic acids known to accumulate in renal failure.

A fluorescent artefact resembling BB-creatine kinase in sera of patients with prostatic disease

A fluorescent zone with mobility towards the anode almost equal to that of human BB-creatine kinase has been detected after electrophoresis on cellulose acetate of sera from each of 28 patients with prostatic carcinoma. The zone is not due to the BB isoenzyme and its appearance does not depend on the presence of substrates of creatine kinase. It therefore appears to be a further example of a fluorescent artefact resembling a creatine kinase ieoenzyme. These observations indicate a need for caution in assessing the possible value of BB-creatine kinase in patients with prostatic disease.