Preliminary investigations on the standardization and quality control for the determination of acid phosphatase activity in seminal plasma.

BACKGROUND: The determination of ACP in seminal plasma was considered as an appropriate biochemical marker to evaluate prostate function, as recommended by the WHO manual. However, few reports on the standardization and quality control for the determination of biochemical markers in seminal plasma have been documented. METHODS: Two frozen samples of seminal plasma with or without phenylmethylsulfonyl fluoride were determined for their acid phosphatase (ACP) levels. The ACP level and sperm concentration of each of 72 samples of seminal plasma obtained at 1000xg for 10 min or 3000xg for 15 min centrifugation were assayed. ACP activity in 10 samples of seminal plasma was measured immediately or standing for 30 min after dilution. The ACP levels in seminal plasma with or without chymotrypsin were also assayed. RESULTS: There was no significant difference of ACP levels (P=0.166) but of sperm concentrations (P=0.000) in seminal plasma obtained by centrifugation at different velocity. ACP activities in seminal plasma measured when standing for 30 min after dilution were significantly lower than those measured immediately after dilution (P=0.001). Both chymotrypsin and freezing-thawing had no apparent effect on the determination of ACP in seminal plasma. CONCLUSION: The results indicated that standing time after dilution and centrifugation velocity should be standardized, and frozen seminal plasma could serve as the quality control products for the determination of ACP activity among different laboratories.

A reference preparation of human prostatic acid phosphatase: purification, characterization and field trials.

Acid phosphatase has been prepared in an apparently pure state by affinity chromatography from human prostatic tissue. When dissolved in an acidic albumin solution, lyophilized and stored at -20 degrees C for up to 2 years, no time-dependent loss of catalytic activity was detectable in the reconstituted material. Accelerated degradation tests also predicted complete stability. A preliminary distribution of the lyophilized preparation to 143 laboratories confirmed its robustness and demonstrated its potential usefulness as a calibrant to unify the results of different methods of measuring acid phosphatase activity.

Development of a stable reference material for prostatic acid phosphatase.

We describe the development of a stable reference material for prostatic acid phosphatase, derived from human prostatic tissue and human seminal fluid. The enzyme was purified by an L-tartramic acid affinity-chromatography technique. Two-dimensional electrophoresis revealed essentially no contaminating proteins, and specific tests revealed no contaminating enzymes. The preparations, in a matrix containing 30 g of human serum albumin and 0.1 mol of sodium acetate per liter, pH 6.0, were studied with respect to stability of both catalytic activity and immunological identity. We conclude that the preparations from either source are satisfactorily stable, and that either is acceptable for use in preparing clinical reference materials. These materials will be used in developing a reference method.

Quality control of acid phosphatase assay improved by direct reconstitution of lyophilized control materials with citric acid.

Current quality control of assays of acid phosphatase (EC 3.1.3.2) with thymolphthalein substrate is inadequate when certain control-suppliers' instructions are followed for reconstituting and stabilizing human lyophilized control material. If such materials are reconstituted with a citric acid solution, then stored frozen, control vial-to-vial variability is minimized, as are losses of activity in freshly reconstituted controls and losses during room-temperature storage of the control material. Effects of pH of the reconstituting solution on the acid phosphatase activity of human lyophilized controls are also discussed.

[Total acid phosphatase. Trials of commercial kits and control sera (author's transl)]. / Phosphatases acides totales. Essais de trousses commerciales et de sérums de contrôle.

The authors estimated the total serum acid phosphatase activity of human serum and that of ten commercial sera using seven commercial kits. The reproducibility and the average of the results, the value of the control sera are given for these seven commercial kits.