Hormone responsiveness of a transplantable rat chondrosarcoma: III. ultrastructural evidence of in vivo hormone dependence.

The effects of growth hormone (GH) and/or cortisone and thyroxine (T4) treatment on the ultrastructure of the transplantable Swarm rat chondrosarcoma grown in hypophysectomized rats were studied. Marked atrophy of the tumor occurred when it was grown in hypophysectomized rats. Maximal restoration of tumor growth in hypophysectomized rats was achieved when cortisone, T4, and GH were administered in combination. An intermediate degree of tumor growth restoration was observed when tumor-bearing hypophysectomized rats were given cortisone and T4 or GH alone. Cortisone and T4 treatment was associated with increased rough endoplasmic reticulum and nucleolar enlargement, while GH treatment was associated with marked dilatation of the endoplasmic reticulum. When GH, cortisone, and T4 were given in combination, a marked increase in exocytotic/pinocytotic vesicles and apparent deposition of cartilage matrix were noted. The data indicate that GH has dramatic influences on the tumors and, when GH, cortisone, and T4 are administered together, these hormones have a synergistic effect on the growth of the Swarm rat chondrosarcoma.