EFFECT OF THYROTROPIN-RELEASING-HORMONE ON MICROTUBULES IN GH(3) CELLS

THE EFFECT Of thyrotropin-releasing hormone (TRH) on the tubulin-micro tubule system in GH(3) cells was investigated. Prolactin (PRL) secreti on by GH(3) cells was stimulated by TRH at 1, 5, and 10 min of incubat ion. The polymerized tubulin levels increased from 0.4 units mu g(-1) protein in control cells to 0.6 units mu g(-1) protein in cells incuba ted with TRH for 1 min. Soluble Protein in cells protein in control ce lls to 0.4 units tubulin levels increased from 0.8 units mu g(-1) prot ein in control cells to 1.2 units mu g(-1) protein in cells exposed to TRH for 5 min. Tubulin levels were similar in control cells and cells treated with TRH for 10 min. These results suggest that TRH-stimulate d PRL secretion is accompanied by a shift in the equilibrium between t ubulin pools.