Voltage dependence of bovine pulmonary artery endothelial cell function.
Vascular mediator synthesis in endothelial cells is Ca2+ sensitive. Bradykinin increases [Ca2+]i by releasing it from intracellular stores and by increasing influx across the plasmalemma. The latter is believed to occur through receptor-operated channels. Although gating of these plasmalemmal channels is voltage-insensitive, we hypothesized that Ca2+ influx would still be dependent on the Ca2+ electrochemical gradient and relative cation permeability. Using cultured bovine pulmonary endothelial cells we therefore measured: membrane voltage (Em) in single cells using the "tight seal" whole cell recording technique, Ca2+i in endothelial cell monolayers using fura-2, and arachidonic acid (AA) release using 3H-AA prior to and following exposure to bradykinin at different [K+]0. Our data indicate that the resting membrane potential of these cells is at least -67 mV in physiological saline and that the background resting membrane properties can be described with a (PNa/PK) ratio of approximately 0.027-0.040. Varying [K+]0 is shown to be an effective means for altering and controlling membrane potential and thus the calcium electrochemical gradient. Increases in [K+]0 lead to a concentration-dependent decrease in the magnitude of the Ca2+ transient and in the relative amount of arachidonic acid released following exposure to bradykinin suggesting that Ca2+ influx through the plasmalemma and AA release are regulated by the Ca2+ electrochemical gradient. In addition, a simple theoretical membrane conductance model is presented which is able to reconcile the wide range in apparent resting membrane potentials which have been reported for endothelial cells.
Campbell
D L
DL
Department of Medicine, Duke University Medical Center, Durham, NC 27710.
Strauss
H C
HC
Whorton
A R
AR
D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004730:Endothelium, Vascular / Q000378:metabolism / Q000502:physiology*; D015640:Ion Channel Gating; D008564:Membrane Potentials; D011188:Potassium / Q000378:metabolism; D011651:Pulmonary Artery / Q000378:metabolism / Q000502:physiology*
D001095:Arachidonic Acids; D016718:Arachidonic Acid; D011188:Potassium; D001920:Bradykinin; D002118:Calcium