Factors Influencing Adenosine 3′,5′-Phosphate Accumulation in Bovine Thyroid Slices

Incubation of bovine thyroid slices in the presence of thyroid-stimulating hormone resulted in increased slice content of adenosine 3',5'-phosphate. This effect of thyroid-stimulating hormone was potentiated by the inclusion of 1 mm theophylline in the incubation medium. In the presence or absence of theophylline, adenosine 3',5'-phosphate accumulation was maximally stimulated by 10 munits per ml of thyroid-stimulating hormone, and the highest nucleotide levels were attained by 3 to 6 minutes of incubation. Levels declined slowly following this early peak. The system responded similarly with two thyroid-stimulating hormone preparations of differing purities. Other peptide hormones tested were inactive. Among various chemical agents tested, only epinephrine was found to stimulate adenosine 3',5'-phosphate accumulation. This effect of epinephrine was half-maximal at 0.2 to 0.3 µm, but the magnitude of the response was small and its duration was brief as compared to the action of thyroid-stimulating hormone. The response to epinephrine was antagonized well by dichloroisoproterenol, but poorly by phenoxybenzamine.