Abstract
Spontaneous milky secretion was found in 24 out of 46 virgin female Sprague-Dawley rats aged 1 year which had been given 30 mg of 9,10-dimethyl-1,2-benzanthracene (DMBA) when 50 days old. The secretory activity was associated with hyperplasia both of mammary epithelium and connective tissue. Additional findings were enlarged adrenals with areas of recent cortical haemorrhage, and ovaries which contained sheets of paraluteal cells. The anterior pituitary of 1 lactating rat contained a small vascular adenoma: no abnormalities were found in the pituitaries of the other animals. It was concluded that these abnormalities could result from increased mammotropic activity of the anterior pituitary.