EXPRESSION OF URINARY H-2 ODORTYPES BY INFANT MICE

The extended H-2 complex of genes in the mouse includes at least three loci that independently specify distinctive body odors, "odortypes," whose differential recognition influences mating choice and affects th e maintenance of early pregnancy. A prime experimental method of ident ifying H-2 odortypes is the specially designed Y-maze in which mice ar e trained, by water deprivation and reward, to distinguish odors condu cted to the arms of the maze from H-2-dissimilar mice or their urines. It is confirmed that H-2-dissimilar infant mice, unlike adult mice, a re not distinguished by trained mice in the Y-maze. However, a previou s conclusion that infant mice do not express H-2 odortypes is shown to be incorrect, because the urines of H-2-dissimilar infant mice, even at 1 day of age, were distinguished in the Y-maze. Thus urine, ingeste d by the mother, clearly could suffice for her to distinguish her own from other H-2-dissimilar pups. Further, urine would seem to be a uniq ue source of H-2 odortypes. If, as we believe, H-2 odortypes represent mostly compound odors composed by H-2 genetic variation in the urinar y output of odorous metabolites, as distinct from simple odors that de pend on chemical differences of single odorants, then the kidney, whic h is not responsible for H-2 odortype specificity, may nevertheless im part a unique character to urinary odortypes by virtue of differential excretion/resorption processing of various constituent odorous metabo lites. In that case, various organs and tissues, among which the hemat opoietic/lymphoid system is known to contribute to H-2 odortype specif icity, may exhibit tissue-specific varieties of H-2 odortypes, their p roducts having not yet been subjected to renal processing.