Inhibitory effect of thyrotropin releasing hormone on spontaneous proliferation of mouse spleen lymphocytes in vitro

The effects of thyrotropin releasing hormone (TRH) and of TRH-like tripeptide pGlu-His-Gly-OH (colon mitosis inhibitor, CMI) on spontaneous proliferation of murine splenocytes were investigated in vitro. The 3H-thymidine incorporation into splenocyte DNA was used as an index of proliferation. It was found that TRH suppressed the proliferation of splenocytes. In contrast, CMI was ineffective by itself but used together with TRH blocked the effect of the latter.