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Adenosine Receptor-Mediated Accumulation of Adenosine 3',5'-Monophosphate in Guinea Pig Thyroid Tissue

National Institute of Arthritis, Diabetes, and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20205

Address requests for reprints to: Dr. J. Wolff, Clinical Endocrinology Branch, National Institute of Arthritis, Diabetes, and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20205.

Abstract

The cAMP content of guinea pig thyroid fragments was increased 2- to 3-fold by adenosine analogs. 5'-iVethylcarboxamide adenosine (NECA), the most potent, caused half-maximal stimulation at 0.7 µUM, whereas 2V6-phenylisopropyl adenosine was much less potent (half-maximal stimulation at 20 µM). Exogenous adenosine by itself was slightly active, and its activity was increased in the presence of adenosine deaminase or transport inhibitors. Although adenosine analogs are partial agonists compared to TSH or the diterpene cyclase activator forskolin, the fractional rate of cAMP accumulation is greater for NECA than for TSH. The stimulatory effect of NECA was antagonized by theophylline. These effects of adenosine and its analogs on cAMP formation in intact thyroid tissue are characteristic of stimulatory adenosine receptors.

Received August 10, 1981.