Dissociation between parathyroid hormone-stimulated cAMP and calcium increase in UMR-106-01 cells.
We used the osteogenic sarcoma cell line, UMR-106-01, to determine whether the rise in free cytosolic Ca2+ concentration ([Ca2+]i) and cellular cAMP following PTH stimulation are able to be regulated independently. For this purpose, we compared the effect of a PTH antagonist, stimulation of protein kinase C, augmentation by prostaglandins, and the time course of desensitization of the two cellular responses. Two x 10(-7) M of the PTH antagonist 8,18Nle 34Tyr-bPTH(3-34) amide ([Nle,Tyr]bPTH(3-34)A) was required to inhibit 10(-9) M bPTH(1-34)-stimulated cAMP generation by 50%. 10(-7) M bPTH(1-34) completely overcame the inhibition induced by 10(-6) M [Nle,Tyr]bPTH(3-34)A. Only 7 x 10(-8) M and 2.7 x 10(-7) M [Nle,Tyr]bPTH(3-34)A were required to half maximally inhibit the [Ca2+]i increase evoked by 3 x 10(-8) and 10(-7) M bPTH(1-34), respectively. In addition, dissociation between [Ca2+]i and cAMP signals was observed when modulation by protein kinase C and prostaglandins was tested. Preincubation of the cells with 10 nM TPA for 5 minutes markedly inhibited the PTH-evoked [Ca2+]i increase. Short incubation with PGF2 alpha augmented the PTH-evoked [Ca2+]i increase. Similar pretreatments had no effect on the PTH-stimulated cAMP increase. Finally, preincubation with 1.5 x 10(-9) M bPTH(1-34) for 20 minutes almost completely blocked the effect of 10(-7) M bPTH(1-34) on [Ca2+]i, while preincubation with 5 x 10(-9) M bPTH(1-34) for 4 hours was required to inhibit the effect of 10(-8) M bPTH(1-34) on cAMP production by 50%. The differences in the regulation of the two PTH-stimulated cellular signaling systems, in particular, the response to antagonists and the time course of desensitization, could be at the level of the PTH receptor(s) or at a postreceptor domain.
Merritt
B S
BS
Division of Nephrology, Cedars-Sinai Medical Center, Los Angeles, California.
Yamaguchi
D T
DT
Green
J
J
Kleeman
C R
CR
Muallem
S
S
D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D015237:Dinoprost / Q000494:pharmacology; D006801:Humans; D012516:Osteosarcoma; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D011956:Receptors, Cell Surface / Q000378:metabolism; D018016:Receptors, Parathyroid Hormone; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D010281:Parathyroid Hormone; D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D018016:Receptors, Parathyroid Hormone; C025076:parathyroid hormone (1-34), bovine; C031617:parathyroid hormone (3-34); C025497:parathyroid hormone (3-34) amide, Nle(8,18)-Nle(34)-; D015237:Dinoprost; D000242:Cyclic AMP; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium