Endocrine testicular function in mink during the first year of life

The endocrine testicular function in mink (Mustela vison) was investigated during the first year of life encompassing puberty, the first mating season and the phase of regression thereafter. The mink, relatively easily accessible as a semi-domesticated animal, was chosen as an example of a mammalian seasonal breeder. In plasma samples from 7 to 17 animals collected on 10 occasions between July and April testosterone and delta4-androstenedione were determined by simultaneous radioimmunoassay. A steady increase of both androgens from November to early March, when the mating season occurs, and a rapid decline to pre-pubertal levels thereafter was observed. The ratio of testosterone to delta4-androstenedione was 1:1 from November to April. These findings parallel the known morphological transitions of the testes.