EFFECTS OF TRH AND TRH-LIKE PEPTIDE PGLU-HIS-GLY-NH2 ON ADRENOCORTICAL CELL-PROLIFERATION IN RATS

The effects of three peptides--colon mitosis inhibitor (CMI), its amid e, and thyroliberin (TRH)--on the adrenocortical cell proliferation we re studied. As an index of cell proliferation, the incorporation of br omodeoxyuridine (BrDU) into adrenocortical cell nuclei was used. It wa s found that: Twelve hours after the injection, only CMI-amide signifi cantly increased the total number of BrDU-immunopositive cell nuclei p er equatorial section of the adrenal cortex. This mitogenic effect was observed separately for the entire section, zona glomerulosa, and zon a fasciculata. TRH stimulated the cell proliferation of the adrenal co rtex 24 h after the injection. Its mitogenic effect was observed for e ntire section and zona glomerulosa. These findings suggest that these two related peptides, TRH and CMI-amide, should be considered as growt h factors for the adrenal cortex.