A method for the determination of tartratelabile, prostatic acid phosphatase in serum.

L(+)-Tartrate strongly inhibits prostatic acid phosphatase (Abul-Fadl and King, 1948, 1949) while having no action on red cell phosphatase. The authors suggested the application of this phenomenon and its diagnostic value as a sensitive test in elucidating doubtful or borderline cases of prostatic cancer. Based on this principle, Fishman and Lerner (1953) described a method for the determination of serum acid phosphatase of prostatic origin. This method requires larger amounts of serum, besides involving the precipitation and separation of proteins, and is more complicated and time-consuming than the method in use here. The method now described is the result of further work on the tartrate-labile phosphatase component and is a modification of the aminoantipyrine (A.A.P.) methods in use in this laboratory (Kind and King, 1954). For borderline cases it probably gives a truer measure of the prostatic part of the serum acid phosphatase than does the formol-stable fraction. A somewhat similar procedure has been described by Daivis and Ward (1956). Reagents Citrate Buffer.-Crystalline citric acid, 21 g., is dissolved in water, 188 ml. of N-NaOH added, the pH adjusted to 4.9 by cautious addition of N-NaOH or N-HCI, and made up to 500 ml. Preserve with a few drops of chloroform in the refrigerator. Substrate (0.01 M-Disodium Phenyl Phosphate).-For the substrate, dissolve 2.18 g. 0.01 M-disodium phenyl phosphate in 1 litre of freshly boiled and cooled distilled water and preserve with a few drops of chloroform in the refrigerator. Stock Phenol Standard (1 mg./ml.).-Pure crystalline phenol, 1 g., is dissolved in a litre of 0.1 N-HCl and preserved in the refrigerator. Dilute Phenol Standard (0.01 mg./ml.).-One millilitre of stock standard diluted to 100 ml. with distilled water is preserved with a few drops of chloroform in the refrigerator. 0.5 N-Sodium Hydroxide.-This is stored in a polythene bottle and filtered when necessary. 0.5 m-Sodium Bicarbonate.-Sodium bicarbonate, 4.2 g., is dissolved in water and made up to 100 ml. The solution is stored in a polythene bottle and filtered when necessary.