Lack of direct evidence for a functional role of voltage-operated calcium channels in juxtaglomerular cells.
In this study we have examined the role of voltage-gated calcium channels in the regulation of calcium in juxtaglomerular cells. Using a combination of patch-clamp and single-cell calcium measurement we obtained evidence neither for voltage-operated calcium currents nor for changes of the intracellular calcium concentration upon acute depolarizations of the cell membrane. Increases of the extracellular concentration of potassium to 80 mmol/l depolarized the juxtaglomerular cells close to the potassium equilibrium potential, but did not alter the intracellular calcium concentration neither in patch-clamped nor in intact Furaester-loaded cells. Moreover, basal renin secretion from a preparation enriched in mouse juxtaglomerular cells and from rat glomeruli with attached juxtaglomerular cells was not inhibited when extracellular potassium was isoosmotically increased to 56 mmol/l. In mouse kidney slices, however, depolarizing potassium concentrations caused a delayed inhibition at 56 mmol/l and a delayed stimulation of renin secretion at 110 mmol/l. Taken together, our study does not provide direct evidence for a role of voltage-activated calcium channels in the regulation of calcium and renin secretion in renal juxtaglomerular cells.
Kurtz
A
A
Physiologisches Institut, Universität, Zürich, Switzerland.
Skott
O
O
Chegini
S
S
Penner
R
R
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000493:pharmacokinetics; D015220:Calcium Channels / Q000502:physiology*; D002463:Cell Membrane Permeability / Q000502:physiology; D004558:Electric Stimulation; D005260:Female; D007606:Juxtaglomerular Apparatus / Q000166:cytology* / Q000378:metabolism / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice
D015220:Calcium Channels; D002118:Calcium