• FETAX;
  • semicarbazide;
  • β-aminopropionitrile;
  • penicillamine;
  • toxic unit analysis


The joint action of binary mixtures of the osteolathyrogens semicarbazide (SC), β-aminopropionitrile (βAPN) and penicillamine (PNC) were determined at malformation-inducing concentrations for Xenopus embryos. Tests were static with renewal every 24 h for the 96-h test period. Simultaneous tests on each individual component of the binary mixtures alone gave baseline malformation data (EC50) for joint action analyses. Toxic unit analysis and isobole diagrams were used to determine the type of joint action for 3:1, 1:1 and 1:3 mixtures of each combination. The joint action was concentration additive (strictly additive) for SC with βAPN and response additive (less-than-additive) for SC with PNC and βAPN with PNC. The joint actions were not changed when only osteolathyrogenic lesions, rather than all types of malformations, were considered. The different specific location and character of PNC lesions, as opposed to those for SC and βAPN, may signify a different type of osteolathyrogenic effect for PNC. The mixture testing approach has potential value in determining compounds that act similarly.