Multiphasic analysis of growth curves for progeny of a somatotropin transgenic male mouse.

Diphasic functions were applied to growth curves for body weight and for tail length of mice that were progeny of a transgenic male mated to random-bred NMRI females. A group of 20 female and male mice with high (H) body weight at week 12, assumed to be transgenic, and a group of 20 with normal (N) body weight, assumed to be non-transgenic, were selected for comparison. Body weight and tail length were measured about weekly from 3 to 26 weeks of age. Body weight for H mice at week 26 averaged 1.6 (females) times and 1.9 (males) times that of N littermates. The H mice averaged 1.3 times the gain in weight in first phase for N mice; H mice averaged 2.0 times the gain in second phase for N mice. Tail length for H mice at week 26 averaged 1.1 times that of N littermates. The H mice averaged .9 times the gain in length in first phase for N mice; H mice averaged 1.5 times the gain in second phase for N mice. For H mice, larger tail-length gain in second phase more than compensated for smaller gain in first phase. The transgenic effect may be different for body weight than for tail length. For body weight, the effect was continuous over the entire 26 weeks. For tail length, however, the effect was to delay growth of the tail.