MONITORING OF CA2-TRANSIENTS IN ELECTRICALLY STIMULATED A7R5 VASCULARSMOOTH-MUSCLE CELLS FILLS THE EXPERIMENTAL GAP BETWEEN KCL-INDUCED DEPOLARIZATION AND PATCH-CLAMP STUDIES()

The effects of electrical field stimulation on [Ca2+]i in the A7r5 vas cular smooth muscle cell line have been monitored with the Ca2+-sensit ive dye fura-2. The experimental set-up allowed high-temporal resoluti on of the [Ca2+]i-measurements and fast application of test solutions. Electrical field stimulation of A7r5 cells in the confluent growth st ate resulted in a transient increase in [Ca2+]i from resting values be low 100 nM to values in the range of some hundred nM. For a given cell , the electrically induced Ca2+-transients were highly reproducible. T he requirement for the presence of extracellular Ca2+ and the sensitiv ity to the Ca2+-antagonist nifedipine and the Ca2+-agonist BAY K 8644 suggest that the Ca2+-transients reflect [Ca2+]i-changes based on Ca2-influx through voltage-dependent L-type Ca2+-channels. Therefore, ele ctrical field stimulation of confluent A7r5 cells provides an easy-to- establish and highly reproducible method for the investigation of the physiology and pharmacology of voltage-dependent Ca2+-channels in inta ct vascular smooth muscle cells, which fills the gap between KCl-induc ed depolarization and the patch-clamp technique.