Effects of TRH and TRH-like peptides on anterior pituitary cell proliferation in rats

Although the effect of TRH on the mitotic activity of anterior pituitary gland has been described, its involvement in the control of pituitary cell growth is still considered controversial: The present paper deals with the effect of a single dose (100 micrograms/kg body wt) of TRH or of TRH-like tripeptides pGlu-His-Gly (colon mitosis inhibitor, CMI) and pGlu-His-Gly-NH2 (CMI-NH2) on anterior pituitary cell proliferation in adult male rats. The incorporation of bromodeoxyuridine (BUdR) into cell nuclei was used as the index of cell proliferation. It was found that TRH and (CMI-NH2) but not CMI increased the BUdR labelling of the anterior pituitary cell nuclei 12 h after peptide administration. These findings support the hypothesis of the positive control of anterior pituitary cell proliferation by TRH, and, possibly, by some other TRH-like peptides.