Preservation of acid phosphatase activity in medico-legal specimens

Vaginal acid phosphatase has been preserved with a protective broth containing, per liter, 50 of bovine albumin, 0.2 g of sodium azide, 10 mmol of phosphate (pH 7.4), and 9.0 g of NaCl. Samples may be maintained at ambient temperature for one month without loss of activity. Several other commonly used preservative methods are compared and are shown to be inadequate. With a constant 2.5 ml volume of the support medium, and use of a sodium thymolphthalein monophosphate method (Worthington Diagnostics), vaginal acid phosphatase activity in non-coital women is less than 10 U/liter of broth, and in recently post-coital women is more than 50 U/liter (242 +/- 104 U/liter). In vivo degradation of vaginal activity follows a nearly logarithmic course until four days after intercourse, when it reaches nearly normal values.