Excreted urine,bladder urine,and the delay of sexual maturation in female house mice

A series of experiments tested effects of excreted and bladder urine of group- and singly-caged female house mice (Mus musculus) on sexual maturation of young female mice caged alone or in groups of eight. Puberty was determined by vaginal smears. A maturation-delaying pherompne was present in bladder urine of all female mice and excreted urine of group-caged females, but not in excreted urine from singly-caged females. Test mice treated with bladder urine homogenized with urethras from singly-caged females matured at the same age as controls. Apparently the urethras or associated glands of singly-caged females produce a substance which deactivates the maturation-delaying pheromone contained in bladder urine.