Growth hormone and insulin-like growth factor-I stimulate hormonal function and proliferation of thymic epithelial cells.
We have investigated the role of GH and insulin-like growth factor-I (IGF-I) in controlling the secretion of thymulin, a hormone produced by thymic epithelial cells (TEC). Thymulin plasma concentrations (mean +/- SD) were increased in 21 patients with acromegaly compared to those in 30 controls, as assessed by bioassay (4.24 +/- 0.97 vs. 2.67 +/- 0.87; P less than 0.001) and RIA (561 +/- 241 vs. 315 +/- 113 pg/L; P less than 0.01). Good correlations were observed between plasma levels of thymulin and IGF-I (P less than 0.001). In vitro experiments demonstrated that both recombinant human GH and IGF-I significantly increased thymulin production in culture supernatants of normal human TEC and a rat TEC line. In parallel, IGF-I also significantly stimulated the proliferation of human TEC, as measured by bromodeoxyuridine incorporation. Additionally, the stimulatory effect of GH on thymulin production was abrogated by both an anti-IGF-I antibody and an anti-IGF-I receptor antibody. These results support a role for GH and IGF-I in the control of thymic hormonal function in man and suggest that the effect of GH may be mediated by local secretion of IGF-I within the thymus.
Timsit
J
J
INSERM U.25, Hôpital Necker, Paris, France.
Savino
W
W
Safieh
B
B
Chanson
P
P
Gagnerault
M C
MC
Bach
J F
JF
Dardenne
M
M
D000172:Acromegaly / Q000097:blood; D000328:Adult; D002455:Cell Division / Q000187:drug effects; D004847:Epithelial Cells; D013006:Growth Hormone / Q000494:pharmacology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008875:Middle Aged; D011994:Recombinant Proteins / Q000494:pharmacology; D013935:Thymic Factor, Circulating / Q000032:analysis / Q000096:biosynthesis; D013950:Thymus Gland / Q000166:cytology* / Q000378:metabolism; D013951:Thymus Hormones / Q000502:physiology*
D011994:Recombinant Proteins; D013951:Thymus Hormones; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D013935:Thymic Factor, Circulating