GENETIC VARIATION IN ADRENAL WEIGHT: STRAIN DIFFERENCES IN THE DEVELOPMENT OF THE ADRENAL GLANDS OF MICE

Abstract

The growth in weight of the adrenal gland was followed in 3 normal strains of mice: A/Cam, CBA/FaCam and Peru. CBA mice have the heaviest adrenals and A mice the lightest. Female mice have larger adrenals than male mice in all 3 strains. This sex-difference is significant in Peru mice before puberty and becomes more pronounced in all 3 strains as development proceeds. Adrenal weight bears a linear relation to body weight in the female mice. The heaviest adrenals, relative to body weight, are found in Peru females and the lightest in A females. The relative growth of the adrenals of male mice can be divided into 2 phases; an early, rapid one and a slower, later one. The ranking of the strains according to the relative weight of the adrenals is different in the 2 phases. Peru mice have the heaviest adrenals during the 1st phase while those of CBA mice are the heaviest in the 2nd. The 2 phases of growth are separated by a transition phase. An absolute fall in adrenal weight occurs during the transition phase in Peru males, but not in A or CBA males. Histologi-cal observations show that degeneration of the X zone coincides with the transition phase in all 3 strains. The 3 strains differ in the age and body weight at which X zone regression takes place in male mice.