Structural requirements for hydantoins and 2-thiohydantoins to induce lymphoproliferative popliteal lym phnode reactions in the mouse

Abstract

The ability of a large number of hydantoins and 2-thiohydantoins to induce primary local lymphoproliferative popliteal lymph node (PLN) reactions has been investigated, as judged by PLN weight enlargement, in an attempt to evaluate the discriminating potential of the PLN reaction to low mol. wt chemicals and establish structure - activity relationships. Among a series of nineteen hydantoins and related compounds only 5,5-diphenylhydantoin (phenytoin), its major metabolite 5-( p-hydroxyphenyl)-5-phenylhydantoin, 5,5-diphenyl-2-thiohydantoin and N-(5-nitro-2-furfurylidene)-1-aminohydantoin (nitro-furantoin) elicited marked PLN reactions in C57BL/6J mice. In DBA/2 mice, PLN responses to the aforementioned compounds were considerably less or virtually absent. A number of hydantoin derivatives and related compounds with one phenyl group and/or other substituents at the 1,3 or 5 position induced only slightly elevated or suppressed PLN responses in C57BL/6J mice. The influence of polar, and lipophilic aliphatic and aromatic substituents at the 5 position were compared among a series of 22 3-methyl-2-thiohydantoin as well as 21 3-phenyl-2-thiohydantoin amino acid derivatives for their ability to elicit primary PLN reactions in C57BL/6J mice. Substitution with only one aromatic group at the 5 position seemed to be necessary to induce PLN enlargements to 2-thiohydantoins already substituted at the 3 position with a methyl group or even more pronounced when substituted with a phenyl group. p-Hydroxylation of 5-benzyl-3-phenyl-2-thiohydantoin significantly diminished the PLN response. In contrast, p-hydroxylation of one of two phenyl groups as in 5-( p-hydroxyphenyl)-5-phenylhydantoin had little effect on lymphoproliferative PLN reactions. The presence of a hydroxyl group in a non-aromatic cyclic substituent as in hexadro-6-hydroxy-2-methyl-3-thioxo-1 H-pyrrolol[1,2-c]imidazol-1-one had no effect on the PLN reaction. A series of aliphatic substituents in the 5 position of 2-thiohydantoins showed that the number of carbon atoms of the substituents as well as the position of side chains in the isomer, rather than the methyl or phenyl group in the 3 position of the 2-thiohydantoin molecule, determined the strength of the PLN enlargement. It is concluded that the PLN weight increase assay appears to be able to discriminate between subtle chemical differrences as studied with a large series of hydantoin and 2-thiohydantoin derivatives. The PLN assay may therefore be useful as a preliminary short-term screening method for identification of (classes of) compounds able to induce lymphoproliferative reactions. However, the PLN assay did not identify all hydantoin derivatives and related compounds with documented lymphoproliferative side effects in humans. The possible significance of polymorphisms in drug metabolism and disposition, factors not accounted for by the local PLN reaction, is discussed.