Abstract
An increase in body weight took place in hypophysectomized immature rats in parabiosis with actively growing rats of the same age with their hypophysis intact. In contract, hypophysectomized rats failed to grow after union with slowly growing older parabionts. It appears likely that in unions of immature rats growth hormone actively secreted by the hypophysis of one member is transferred to its hypophysectomized partner to stimulate its growth. The average per cent increase in body weight in immature hypophysectomized rats during a period of 28 to 30 days was 116.4%, while that of their partners with hypophysis intact was 134.4%, the ratio of the two values being almost constant in different pairs (0.881±0.018, on the average), regardless of the age at union, the strain and sex of parabionts, and various treatments given to the animals. The growth of immature rats with hypophysectomized parabionts was retarded as compared with that of single intact rats as well as those with partners having hypophysis intact. These findings were discussed in relation to the regulatory mechanism of growth hormone secretion.
