The effect of growth hormone on the incorporation of labeled sulfate into the chick embryo femur in tissue culture.

genesis, mechanism of the actions of the hormone on skeletal growth has been under study for many years. Despite these extensive studies the mechanism remains still obscure. Ellis et al.(1953) showed that the incorporation of radiosulfate into cartilage of immature growing rats was greatly reduced by hypophysectomy and restored by growth hormone administration. Denko and Bergenstal (1955) also presented similar observations. Recently Salmon and Daughaday (1957) have reported that the in vitro uptake of radiosulfate by cartilage from rats is reduced by hypophysectomy and that the reduced radiosulfate uptake can be restored by growth hormone administered in vivo but not by the in vitro addition of growth hormone. And they suggested a growth hormone induced factor, termed sulfation factor, in plasma. Furthermore, Daughaday et al.(1959) have observed the decreased sulfation factor activity in sera of patients with hypopituitarism and the increased one in those of patients with acromegary. The fixation of radiosulfate will provide a useful index of cartilage metabolism, for labeled sulfate is incorporated exclusively into chondroitin sulfate that is the essential mucopolysaccharide of cartilage. Layton (1950) examined the radiosulfate fixation by various chick embryonic tissues including tibia maintained in vitro. For cultivation of skeletal tissues in vitro, on the other hand, one of the authors ( Endo, 1960) has standardized the roller-tube culture method without plasma. And, using the culture method, the active principles from the bovine parotid gland (Ito and Endo, 1956) and from human mixed saliva (Ito et al., 1960) have been successfully demonstrated to exert direct actions in vitro on the calcification of chick embryo femur. In this report, on these lines, the effect of pituitary growth hormone on skeletal tissue was examined mainly by measuring the incorporation of 35Ssulfate into the 9-day chick embryo femora growing in vitro. A part of the results have been contributed as a letter to the editors of this journal (Ito et al., 1959).