Cholinergic regulation of voltage-dependent Ca2+ channels in porcine tracheal smooth muscle cells.
To investigate cholinergic regulation of voltage-dependent Ca2+ channels (VDCs) in airway smooth muscle, we measured inward currents through VDCs in enzymatically dispersed porcine tracheal smooth muscle cells using conventional (10 mM Ca2+ as charge carrier) and nystatin-perforated (5 mM Ba2+ as charge carrier) whole cell patch clamp techniques. Carbachol (CCh) had significant and dose-dependent inhibitory effects on inward currents (12% with 10(-7) M and 42% with 10(-6) M) in perforated whole cell clamp experiments, but had no effect on currents in conventional whole cell experiments. CCh also shifted the steady-state inactivation curve to more negative potentials. Further experiments tested the hypothesis that CCh inhibits VDCs in part by the activation of protein kinase C (PKC). Phorbol 12,13-diacetate, an exogenous PKC activator, inhibited currents through VDCs. and calphostin C, a specific PKC inhibitor, antagonized the inhibitory effect of CCh. Furthermore, intracellular exposure to the activating PKC fragment 530-558, using a pipette perfusion technique, also inhibited currents through VDCs. We conclude that cholinergic receptor stimulation can inhibit inward Ca2+ currents through VDCs of porcine tracheal smooth muscle and that this effect may be mediated in part by activation of PKC.
Yamakage
M
M
Department of Anesthesiology, Johns Hopkins Medical Institutions, Baltimore, Maryland 21205, USA.
Hirshman
C A
CA
Croxton
T L
TL
D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D004594:Electrophysiology; D004789:Enzyme Activation; D009130:Muscle, Smooth / Q000166:cytology / Q000502:physiology*; D009761:Nystatin / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000378:metabolism; D011950:Receptors, Cholinergic / Q000502:physiology*; D013552:Swine; D014132:Trachea / Q000166:cytology / Q000502:physiology*
D015220:Calcium Channels; D011950:Receptors, Cholinergic; D009761:Nystatin; D002217:Carbachol; D011493:Protein Kinase C