Comparison of the effects of the growth factor produced by Spirometra mansonoides and growth hormone in diabetic-hypophysectomized rats: lymphoid tissue.

Growth and development of the thymus is dependent on secretions from the anterior pituitary, presumably growth hormone. Diabetes mellitus is known to reduce immunological competence. These studies compare the effects of bovine growth hormone (bGH) and the growth factor produced by plerocercoid larvae of the tapeworm, Spirometra mansonoides, on metabolism of lymphoid tissue, thymus and spleen, in hypophysectomized rats made diabetic with a single intraperitoneal injection of alloxan. Whereas the control diabetic-hypophysectomized rats gradually lost weight throughout the experimental period, both bGH and plerocercoid infection caused significant weight gains during the experimental period. The diabetic-hypophysectomized rats treated with bGH had significantly heavier thymuses and spleens than controls. Plerocercoid infection also caused significant increases in thymus weights. Both bGH and plerocercoids stimulated the metabolic activity of thymocytes isolated from treated rats and tested for their ability to incorporate 3H-thymidine into DNA in vitro. Thus, these growth factors have similar effects on the lymphoid tissue of diabetic-hypophysectomized rats which are apparently independent of normal insulin levels. Whether this anabolic effect is direct or mediated by somatomedin remains to be determined.