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.
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(-9) M, 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.
Cell Biology Research Unit, Gunma University, Maebashi, Japan.
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YQ
Zhang
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Mine
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Kojima
D000818:Animals; D004305:Dose-Response Relationship, Drug; D005947:Glucose / Q000378:metabolism*; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D010477:Perfusion; D011506:Proteins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments; D011506:Proteins; C066077:parathyroid hormone-related protein (1-84); D005947:Glucose