Studies on the effect of parathyroid hormone (1–84) on glucose output in the liver: Comparison of effects in isolated hepatocytes and in perfused liver

Abstract

This study was conducted to determine the action of parathyroid hormone (1–84) (PTH(1–84)) on glucose output both in perfused liver and in isolated hepatocytes. In isolated rat hepatocytes, PTH(1–84) stimulated glucose output in a concentration-dependent manner. The action was detected at 10 −11 M and, at 10 −9M, PTH produced its maximal effect. The magnitude of the maximal effect of PTH(1–84) was about 65% of that of phenylephrine. In contrast, PTH(1–84) had no effect on glucose output in perfused rat liver. Concentration of PTH(1–84) in effluent of perfused liver was less than that in the inflow. However, when the effluent obtained from liver perfused with 10 nM PTH(1–84) was added to isolated hepatocytes, a considerable amount of glucose was released, which was reversed by PTH(7–34), a competitive inhibitor of PTH receptor. These results indicate that PTH(1–84) increases glucose output in isolated hepatocytes but not in intact liver. It is suggested that the action of PTH(1–84) is blocked in intact liver by a yet unknown mechanism.