Once taken off the compound, the mice continued to make sperm. The mechanism of action includes blocking the conversion of vitamin A into its active form retinoic acid which binds to retinoic receptors which is needed to initiate sperm production.[31][32] This can be done, for instance, by blocking an aldehyde dehydrogenase called RALDH3 (ALDH1A2), which converts retinaldehyde into retionic acid in testes. Past attempts to do this failed because the blocking compounds were not sufficiently specific and also blocked other aldehyde dehydrogenases, such as those responsible for the alcohol metabolism, causing serious side effects.[33] Another way is blocking retionic receptors themselves, although it can also have serious side effects.[31]