RESUMO
The genetic association of the agouti (a) locus with mouse adrenal X zone morphology on a specific genetic background has been suggested. To confirm this, the adrenal cortices of virgin females were compared histologically between BALB/c (A/A) and its mutant, BALB/c-a/a (a/a). The X zone was similar in the number of constituting cell layers, but different in morphology between the A/A and a/a genotypes. At 70 days of age, it was constituted of vacuolated cells exclusively in A/A and of non-vacuolated and a few vacuolated cells in a/a. At 140 days of age, the X zones contained only vacuolated cells in both genotypes. Therefore, the a (non-agouti) allele might have 2 effects upon the X zone morphology on the BALB/c background; the a allele might suppress vacuolation and delay its onset. However, the zona reticularis seemed to have no association with this locus.