Specific inhibition of long-lasting, L-type calcium channels by synthetic parathyroid hormone.
The effect of an active synthetic N-terminal fragment of bovine parathyroid hormone (bPTH), bPTH-(1-34), on Ca2+ channels was studied in mouse neuroblastoma cells (N1E-115). With the whole-cell variation of the patch-clamp technique, T (transient) and L (long-lasting) types of Ca2+ currents were identified. Pharmacological characterization showed that the L current was amplified by the Ca2+ channel stimulator BAY K-8644, but the T current was unaffected. The administration of bPTH-(1-34) produced dose-related inhibition of the L current, which could be reversed by BAY K-8644. The peptide had no effect on the T current. In addition, use of the fluorescent indicator fura-2 showed that bPTH-(1-34) inhibited the KCl-stimulated increase in intracellular free Ca2+ in neuroblastoma cells with L channels but not in cells with T channels. An inactivated (oxidized) preparation of bPTH-(1-34) failed to affect the L current. High-affinity binding of labeled PTH analog to these neuroblastoma cells was also demonstrated. In addition, bPTH-(1-34) inhibited the L current in cultured vascular smooth muscle cells from rat tail artery. These data indicate that, in some tissues, PTH can act as an endogenous blocker of Ca2+ entry.
Pang
P K
PK
Department of Physiology, University of Alberta, Edmonton, Canada.
Wang
R
R
Shan
J
J
Karpinski
E
E
Benishin
C G
CG
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000502:physiology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009447:Neuroblastoma; D010281:Parathyroid Hormone / Q000378:metabolism / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism; D018016:Receptors, Parathyroid Hormone; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000502:physiology*
D015220:Calcium Channels; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D018016:Receptors, Parathyroid Hormone; C025076:parathyroid hormone (1-34), bovine; D011189:Potassium Chloride; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester