Galactin Content of the Rat Pituitary. ∗

Abstract

We reported 1 that the normal male rat pituitary contains an appreciable amount of the lactogenic hormone and that the injection of the estrogenic hormone definitely increases the galactin content of the pituitary gland.

Employing the same technique as that which we described in the paper referred to above we have extended the study of the galactin content of rat pituitary glands. The results are summarized in Table I.

From the table one can see that as the male rat continues to grow the pituitary gland likewise increases in weight. The bird units of galactin per pituitary gland increase as the animal matures, but this is due largely to the increase in the weight of the gland as one notices that the galactin concentration remains quite constant. The daily injection of 500 international units of Oestroform B into male rats for 7 days increases the weight of the pituitary gland and increases the galactin content of the gland while the content in bird units of galactin per mg. of fresh pituitary tissue remains nearly constant. The injection of thyroxine in increasing dosages decreases the weight of the pituitary glands, decreases the total potency of the glands, and decreases the galactin concentration per mg. of fresh pituitary tissue. The injection of thyroxine at the same level each day, 0.01 mg., produces the same results but to a less extent. Male rats castrated for 60 days possess much larger pituitary glands; the bird units of galactin per pituitary gland, however, remain constant.

The pituitary gland from the immature female rat contains about 3 times the amount of galactin of the immature male rat, this increased galactin content being accompanied by an increased glandular weight and an increased concentration of the galactin. As the female rat matures there is an increase in weight of the pituitary gland as well as an increase in concentration of galactin. At 12 days of pregnancy there is a decrease in the number of bird units of galactin per pituitary gland as compared with glands from normal estrous cycle females, and at 21 days pregnancy there is an increase in potency of the glands as compared with those from rats pregnant for 12 days. Forty-eight hours postpartum there is a doubling of the galactin content of the pituitary gland over that of the glands from either the normal estrous cycle female or the female pregnant for 21 days. At 10 days postpartum the galactin content of the glands decreases somewhat, being about midway between the glands from 48 postpartum rats and glands from normal estrous cycle females.