Subcapsular intratesticular assay: a preliminary screening method for putative male antifertility drugs

The subcapsular intratesticular assay was developed for the preliminary screening of male antifertility agents. In the assay, small amounts of the test sample are injected twice, 1 week apart just beneath the tunica albuginea of the testes of rats. The rats were killed within 3 weeks of treatment to examine epididymal spermatozoa and the histology of the testis and epididymis. There is an excellent agreement between this method and the modified MB-50 assay developed by the World Health Organization. To date, more than 300 samples have been assayed, of which the results of 10 plant-derived compounds are reported here. Not one active sample has been missed as confirmed by the modified MB-50 method, although one compound which was positive in the subcapsular assay did not show antifertility action in the in-vivo assay. Compared with the latter assay, the advantages of this method are: simplicity, time-saving, rat-saving and the need for far smaller amounts of test sample. The absence of false-negative results makes the subcapsular intratesticular assay applicable as a preliminary screening method to test potential male fertility regulating agents.