Effects of three fragments of parathyroid hormone on calcium channel currents in neonatal rat ventricular cells.
The effects of different fragments of bovine parathyroid hormone, bPTH-(1-34), bPTH-(1-84) and bPTH-(3-34), on two types of calcium channel currents in neonatal rat ventricular cells were compared in the present study. bPTH-(1-34) increased the amplitude of L channel currents, but not of the T channel currents. This effect of bPTH-(1-34) was sustained after a complete washout of the peptide from the bath. The intact PTH molecule, bPTH-(1-84), also increased L channel currents but not affecting T channel currents. While bPTH-(3-34) did not affect the amplitudes of either L or T channel currents by itself, pretreatment of cells with bPTH-(3-34) abolished the effects of both bPTH-(1-34) and bPTH-(1-84) on L channel currents. Moreover, the kinetics of L channel currents in the presence of bPTH-(1-34) or bPTH-(3-34) were different. bPTH-(1-34) increased the time constant of activation, but not of inactivation, of L channel currents from 1.8 to 2.5 ms (P < 0.05). In contrast, bPTH-(3-34) decreased the time constant of inactivation, but not of activation, of L channel currents from 159 to 117 ms (P < 0.05). These results indicate that different fragments of PTH exert different effects on the amplitudes or kinetics of cardiac calcium channel currents.
Wang
R
R
Department of Physiology, University of Alberta, Edmonton, Canada.
Karpinski
E
E
Pang
P K
PK
D000818:Animals; D000831:Animals, Newborn; D015220:Calcium Channels / Q000502:physiology*; D002478:Cells, Cultured; D006352:Heart Ventricles; D015640:Ion Channel Gating / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D009543:Nifedipine / Q000494:pharmacology; D010281:Parathyroid Hormone / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D010446:Peptide Fragments / Q000494:pharmacology; D051381:Rats; D013329:Structure-Activity Relationship
D015220:Calcium Channels; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D009543:Nifedipine