VOLTAGE-GATED CA2-LIKE CELLS( CURRENTS IN RAT GASTRIC ENTEROCHROMAFFIN)

Enterochromaffin-like (ECL) cells are histamine-containing endocrine c ells in the gastric mucosa that maintain a negative membrane potential of about -50 mV, largely due to voltage-gated K+ currents [D. F. Loo. G. Sachs, and C. Print. Atn. J. Physiol. 270 (Gastrointest Liver Phys iol. 33): G739-G745, 1996]. The current study investigated the presenc e of voltage-gated Ca2+ channels in single ECL cells. ECL cells mere i solated from rat fundic mucosa by elutriation, density gradient centri fugation, and primary culture to a purity >90%. Voltage-gated Ca2+ cur rents were measured in single ECL cells using the whole cell configura tion of the patch-clamp technique. Depolarization-activated currents w ere recorded in the presence of Na+ or K+ blocking solutions and addit ion of 20 mM extracellular Ca2+. ECL cells showed inward currents in r esponse to voltage steps that were activated at a test potential of ar ound -20 mV with maximal inward currents observed at +20 mV and 20 mM extracellular Ca2+. The inactivation rate of the current decreased wit h increasingly negative holding potentials and was totally abolished a t a holding potential of -30 mV, Addition of extracellular 20 mM Ba2instead of 20 mM Ca2+ increased the depolarization-induced current and decreased the inactivation rate. The inward current was fully inhibit ed by the specific L-type Ca2+ channel inhibitor verapamil (0.2 mM) an d was augmented by the L-type Ca2+ channel activator BAY K 8644 (0.07 mM). We conclude that depolarization activates high-voltage-activated Ca2- channels in ECL cells. Activation characteristics, Ba2+ effects, and pharmacological results imply tile presence of L-type Ca2+ channel s, whereas inactivation kinetics suggest the presence of additional N- type channels in rat gastric ECL cells.