Non-thyrotropic pituitary cells in culture convert T4 to T3

Abstract

Although intrapituitary conversion of T4 to T3 has been shown in rat pituitary homogenates, this deiodination has not been demonstrated in non-thyrotropic pituitary cells. GH3 cells, which produce growth hormone and prolactin, were used to demonstrate formation of T3 from T4 in monolayer culture. During a 1 hr incubation, the amount of T3 generated increased with increasing T4 substrate concentrations, reaching a plateau after 0.9 μM T 4. When dithiothreitol was added to the medium, production of T3 doubled at all concentrations of T4. T3 production in the presence of 2 μM T4 increased from .23 nM after 0.5 hr incubation to .8 nM after 3 hr incubation. Deiodination by this nonthyrotropic rat pituitary tumor cell is markedly enhanced by a thiol-protective agent.