Prostacyclin Stimulation of Adenylate Cyclase Activity in Human Thyroid Membranes

Summary

Effect of prostacyclin (PGI₂) on adenylate cyclase activity in human thyroid membranes was examined. PGI₂ caused a dose- and time-dependent production of cyclic AMP (cAMP) with high potency. When GTP was added in concentrations up to 100 uM, the activation of adenylate cyclase by PGI₂ was increased. In the assay medium containing 3 mM ATP, 10 uM GTP and nucleotide regenerating system, the replacement of Mg²⁺ by increasing concentrations of Mn²⁺ caused a progressive loss of PGI₂ as well as TSH-stimulated adenylate cyclase activities, while high concentrations of Mg²⁺ (12 or 18 mM) slightly suppressed the activity stimulated by either PGI₂ or TSH. Both agents had an additive effect on the stimulation of adenylate cyclase activity in the presence of either 6 mM Mg²⁺ or 6 mM Mn²⁺. Gamma-globulin fraction containing non-stimulatory TSH receptor antibody which was prepared from a patient with chronic thyroiditis, suppressed only TSH- but not PGI₂-stimulation of the adenylate cyclase activity. These results suggest that PGI₂ can stimulate the adenylate cyclase activity in human thyroid tissue, and that PGI₂-stimulation may be mediated by the different system from TSH-dependent one.

Human Thyroid Membranes - Prostacyclin - TSH - Adenylate Cyclase