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We developed two lines of guinea pigs, one as model animals for bronchial asthma with bronchial hypersensitivity and the other with hyposensitivity as a control. In the last four years, the bronchial hypersensitive line (BHS) and hyposensitive line (BHR), both derived from Hartley strain guinea pigs, have been selected by using bronchial reactivity to acetylcholine and to histamine as parameters. Both lines have reached the F6 generation. The following results were obtained with the two lines: 1) Sib and cous in matings, and mating of selected consanguineous individuals were adopted in breeding BHS and BHR. The breeding started with six families, each, but in the F6 generation the number of families decreased to two in each line. 2) Appearance rates of hyper- or hyposensitivity to acetylcholine and histamine increased with successive generations in both lines, which had been completely separated by the F6 generation. 3) Coefficients of inbreeding in BHS and BHR in the F6 generation ranged from 42% to 45% in the former and 42% in the latter. 4) Heritabilities (h2) of BHS and BHR for the appearance rates of sensitivity to acetylcholine were presumed to be 0.54 in the former and 0.69 in the latter. 5) No difference in the body weight of 0, 20, and 40 day-old BHS was observed in any generation. On the other hand, the body weight of 20 and 40 day-old BHR tended to decrease with successive generations. 6) Mean litter sizes of BHS and BHR in each of the generations ranged from 2.24 to 3.47 animals in the former and from 2.63 to 3.38 animals in the latter.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective Breeding of Two Lines of Guinea Pigs Differing in Bronchial Sensitivity to Acetylcholine and Histamine Exposure