Inhibitory effect of somatostatin on the basal and TSH-stimulated 3H-thymidine incorporation into rat thyroid lobes incubated in vitro

The effects of somatostatin on the spontaneous and TSH--stimulated incorporation of tritiated thymidine into the rat thyroid lobes incubated in vitro were investigated. The rate of 3H-thymidine incorporation was used as an index of thyroid follicular cells (TFC) proliferation. It was shown that: 1) somatostatin, at a concentration of 10(-7)M, decreased 3H-thymidine incorporation into DNA of TFC, 2) the highest somatostatin concentration, as tested in this study (10(-6)M), produced a similar decreasing effect; the decrease, in this case, did not attain significance vs. controls, 3) somatostatin, when employed together with TSH, suppressed the stimulatory effect of the latter hormone on 3H-thymidine incorporation into DNA of thyroid lobes.