Mammary gland development was studied in castrated, alloxan-diabetic rats injected with testosterone. After twentyone days of daily injections with 0.5 mg. testosterone propionate, the mammary glands of the diabetic rats showed extensive lobule-alveolar development which was even more pronounced than in nondiabetic controls injected withthe same dose of testosterone. This result shows that a normal secretion of insulin is not a prerequisite for lobule-alveolar development in the rat mammary gland. The more extensive lobule-alveolar development in the diabetic rats can be explained by a higher production of adrenal steroids in these rats.
From the result of the present investigation and our previous study on alloxan-diabetic rats injected with ovarian hormones it seems likely that there is inadequate production of prolactin in alloxan-diabetic rats.
