Endogenous cyclic AMP in thyroid cell culture. Effect of thyroid-stimulating hormone and dibutyryl cyclic AMP

We have studied the variations of endogenous cyclic AMP levels in thyroid cells cultured over a period of 7 days in several conditions: in the presence of thyroid-stimulating hormone or dibutyryl cyclin AMP which both promote the aggregation of isolated cell into follicles, and in their absence when cells develop as a typical monolayer. In follicle-forming cells, the cyclic AMP level was found to rise during the first day of culture, then to fall rapidly. In monolayer-forming cells, the cyclic AMP content slightly increases attaining the same level as found in other cells at the fourth day, which remains stable till the seventh day. We have investigated the response of these cells to the acute effect of thyroid-stimulating hormone: only cells cultured in the presence of dibutyryl cyclic AMP retain the capability of increasing their cycli AMP concentration whereas monolayer-forming cells do not preserve this quality of thyroid cells.