Hormone responsiveness of a transplantable rat chondrosarcoma. I. In vitro effects of growth hormone-dependent serum factors and insulin.

Serum somatomedins and insulin stimulate transport processes and macromolecular synthesis in cartilage. The in vitro effects of serum somatomedins and insulin on amino acid transport and macromolecule synthesis in the Swarm rat chondrosarcoma were studied to determine if malignant transformation alters the responsiveness of chondrocytes to these factors. Amino acid transport was assessed by alpha-aminoisobutyrate uptake. Macromolecule synthesis was estimated by radiolabeled precursor incorporation into RNA, total proteins, and proteoglycan. Serum from normal rats and GH-treated hypophysectomized rats stimulates alpha-aminoisobutyrate uptake and macromolecule synthesis in the rat chondrosarcoma. Hypophysectomized rat serum stimulates these events marginally or not at all. Thus, the chondrosarcoma responds in vitro to GH-dependent serum factors. Additionally, insulin stimulates in vitro amino acid transport and macromolecule synthesis in the rat chondrosarcoma. These data demonstrate that, in vitro, the Swarm rat chondrosarcoma is a hormone-responsive tumor.