title: Influence of muscarinic agonists and tyrosine kinase inhibitors on L-type Ca(2+)Channels in human and bovine trabecular meshwork cells.
abstract: Trabecularmeshwork (TM), a smooth muscle-like tissue with contractile properties, is involved in the regulation of aqueous humor outflow. However, little is known about the regulation of Ca(2+)influx in trabecular meshwork cells. We investigated the influence of acetylcholine and tyrosine kinases on Ca(2+)conductances of bovine TM (BTM) and human TM (HTM) cells using the perforated-patch configuration of the patch-clamp technique and measurements of intracellular free Ca(2+)([Ca(2+)](i)). Depolarization of the cells in the presence of 10 m m Ba(2+)or Ca(2+)led to an activation of inward currents at potentials positive to -30 mV with characteristics typical of L-type Ca(2+)currents: when using 10 m m Ba(2+), maximal inward current and inactivation time constant (tau) increased; the L-type Ca(2+)channel blocker nifedipine (1 microm) reduced and the L-type Ca(2+)channel agonist BayK8644 (5 microm) enhanced maximal inward current. Acetylcholine (100 microm) and carbachol (1 microm) led to an increase in inward Ba(2+)current whereas application of the tyrosine kinase inhibitors genistein (50 microm) and lavendustin A (20 microm) resulted in a decrease in inward current. The application of daidzein (10 microm), an inactive analog of genistein had no effect. Depolarization of the cells with 135 m m K(+)or direct stimulation of L-type channels by application of BayK 8644 led to an increase in [Ca(2+)](i). Carbachol (1 microm) induced an increase in [Ca(2+)](i)which was decreased by application of the tyrosine kinase inhibitor genistein (50 microm). We conclude that HTM and BTM cells express voltage-dependent L-type Ca(2+)channels that influence intracellular Ca(2+)concentration and thus may modulate TM contractility. The activity of L-type Ca(2+)currents is influenced by muscarinic agonists and tyrosine kinases.
authors.affiliation: Institut für Klinische Physiologie, Universitätsklinikum Benjamin Franklin, Freie Universität Berlin, Hindenburgdamm 30, Berlin, 12200, Germany. steinhausen@ukbf.fu-berlin.de
authors.forename: K
authors.initials: K
authors.lastname: Steinhausen
authors.forename: F
authors.initials: F
authors.lastname: Stumpff
authors.forename: O
authors.initials: O
authors.lastname: Strauss
authors.forename: H
authors.initials: H
authors.lastname: Thieme
authors.forename: M
authors.initials: M
authors.lastname: Wiederholt
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000187:drug effects*; D002217:Carbachol / Q000494:pharmacology; D002417:Cattle; D018679:Cholinergic Agonists / Q000494:pharmacology; D046508:Culture Techniques; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D019833:Genistein / Q000494:pharmacology; D006801:Humans; D018721:Muscarinic Agonists / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D014129:Trabecular Meshwork / Q000187:drug effects* / Q000378:metabolism; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D020746:Calcium Channels, L-Type; D018679:Cholinergic Agonists; D004791:Enzyme Inhibitors; D018721:Muscarinic Agonists; D014665:Vasodilator Agents; D002217:Carbachol; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D000109:Acetylcholine; D002118:Calcium