Chemosterilant, specificity

Aminopterin, methotrexate, S-fluorouracil, 5-fluoro-orotic acid, tepa, metepa, and apholate all sterilized at the higher concentration, but only the antimetabolites sterilized at the lower concentration. Whenever a compound induces sterility, a second series of tests is run to determine the range of effective concentrations. Some antimetabolites sterilized at concentrations as low as 0.0025%, whereas the minimum for alkylating agents was 0.25%. In the third series of tests, the specific sex sterilized is determined. The chemosterilants are presented in the food at sterilizing concentrations to individual sexes of flies. These flies are then mated with normal flies of the opposite sex. All the chemicals mentioned above sterilized the females, but aminopterin and methotrexate failed to sterilize the male flies, and 5-fluorouracil produced male sterility in only a few tests. Tepa, 5-fluoro-orotic acid, metepa, and apholate, when included in the food, regularly sterilized both sexes. Because of the inability of aminopterin, methotrexate, and 5-fluorouracil to sterilize males, these compounds were not considered further. 

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