Abstract
Previous observations 1 indicated that pituitary glands from lac-tating guinea pigs contained more lactogen than did glands from sexually mature, non-pregnant, and non-lactating guinea pigs. The intent of this assay work was to compare the lactogen content of pituitary glands from guinea pigs sacrificed in estrum, diestrum, early pregnancy, late pregnancy, and lactation.
Series I. Animals were paired on the basis of body weight, the average body weight of each group being approximately the same. Six guinea pigs were sacrificed in each of the previously mentioned stages.
Series II. Six animals were sacrificed in early pregnancy, late pregnancy, and lactation. However, the average body weights of these groups varied considerably. Lactating animals in both series were sacrificed on the 11th day of the lactation period, the young having been removed 15 hours previously.
The pituitary glands were removed, weighed, and assayed for their lactogen content by injecting the suspended tissue intradermally over the crop glands of common pigeons.
In Series I the pituitary gland of an animal in one group was compared with the gland from an animal of similar body weight in each of the 4 other groups. In Series II the pituitary gland of an animal in one group was compared with the gland from an animal in each of the 2 other groups. In each comparison one-fourth of a pituitary gland was injected over the right crop gland of 3 pigeons and one-fourth of another pituitary gland over the left crop gland of the same 3 pigeons:
In Series I the pituitary glands from guinea pigs in estrum contained slightly more lactogen than did those from animals in diestrum and early pregnancy and slightly less lactogen than did those from guinea pigs in late pregnancy and lactation.
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