An hormonally controlled serum factor stimulates thymidine incorporation into lectin-activated lymphocytes

摘要

The in vitro stimulation of 3H-thymidine (T) incorporation into lectin-activated human lymphocytes was studied in presence of various sera and compared to a normal reference serum (1 U/ml activity). The mean precision of the assay was 5%. The interassay variability was 0.06 U/ml (95% confidence). Compared to 19 normal adults (mean ± SEM : 1.04 ± 0.06 U/ml), serum T activity was increased in 3 acromegalics (2.63 ± 0.48, p < 0.001) and decreased in 17 hypopituitary dwarfs (0.37 ± 0.04, p<0.001), T activity being significantly less in them than in 17 constitutional dwarfs in the same age range (1.51 ± 0.13, p<0.001). In hypopits, a single IM hGH injection increased the T activity(p < 0.001) after 24 to 48 h. Only high supraphysiological doses of hGH, insulin and T3 were slightly effective. Purified Somatomedin A diluted at physiological levels increased the T incorporation and its effects were enhanced in the presence of serum. These data demonstrate that 3H-T incorporation into activated lymphocytes is stimulated by a GH-dependent serum factor. They suggest to use this technique for a rapid, accurate and sensitive evaluation of serum somatomedin activity.