Selective alpha(1A)-Adrenoceptor Stimulation Induces Mueller's Smooth Muscle Contraction in an Isolated Canine Upper Eyelid Preparation

Purpose: It has been demonstrated that in patients with aponeurotic blepharoptosis, alpha(1)-adrenoceptor stimulation causes the contraction of the upper eyelid tarsal smooth muscle (Mueller's muscle) and opening of the eye. However, alpha(1)-adrenoceptor subtypes mediating the contraction of Mueller's muscle are still unclear. This study was designed to identify the alpha(1)-adrenoceptor subtypes in Mueller's muscle. Materials and Methods: A newly developed canine upper eyelid preparation was retrogradely perfused with a drug-containing Krebs-Henseleit solution through the angular vein in a temperature-controlled organ chamber. The contraction of the preparation was measured with a force-displacement transducer. Results: Phenylephrine, an alpha(1)-adrenoceptor agonist, increased the upper eyelid contractile force in a dose-dependent manner (K(0.5) = 110 nmol). Interestingly, the contraction in response to phenylephrine was persistent and hardly recovered to a base line level for more than 100 min after washout of the drug. WB4101 (100 nM), an alpha(1A)- and alpha(1D)-adrenoceptor antagonist, but not BMY7378 (100 nM), a selective alpha(1D)-adrenoceptor antagonist, competitively inhibited the phenylephrine-induced contraction. ABT-866, a selective alpha(1A)-adrenoceptor agonist, increased the upper eyelid contractile force as effectively as phenylephrine in a dose-dependent manner (K(0.5) = 190 nmol), and the contraction continued again for more than 100 min. Conclusion: These results suggest that selective alpha(1A)-adrenoceptor agonists, such as ABT-866, induce the sustained Mueller's muscle contraction and may be useful in pharmacological treatment of blepharoptosis.ArticleCURRENT EYE RESEARCH. 35(5):363-369 (2010)journal articl

Thrombin Activates Ca2+-permeating Nonselective Cation Channels through Protein Kinase C in Human Umbilical Vein Endothelial Cells

We analyzed Ca-permeating nonselective cation channels (NSCs)mediating thrombin-induced contraction of human umbilical vein endothelial cells (HUVECs). A Ca chelater, BAPTA-AM (10μM), significantly inhibited the thrombin-induced contraction of HUVECs.Thrombin induced inward currents at -60 mV in the presence of intracellular MgATP. Removal of extracellular Caﾌﾞｸﾞsignificantly decreased the currents. A selective phospholipase C inhibitor, U73122 (1μM) but not its inactive analogue, U73343 (1μM) almost completely inhibited the currents. Neither a selective inhibitor of Caﾌﾞｸﾞ-ATPase of endoplasmic reticulum, thapsigargin (1μM)nor a diacylglycerol analogue, 1-oleoyl-2-acetyl-glycerol (30μM)activated the currents. However, a selective protein kinase C inhibitor, bisindolylmaleimide I (500 nM) significantly inhibited the currents.The thrombin-induced currents were significantly inhibited by SKF96365 (50μM)but not by La(1mM), ruthenium red (10μM) or flufenamic acid (100μM). As assessed with RT-PCR, HUVECs expressed transient receptor potential(TRP)M4,7,TRPV1,2,4,TRPC1,4 and 6 subunits of NSCs.These results indicate that thrombin activates Ca-permeating NSCs containing TRPC4 through protein kinase C in HUVECs. Thus,drugs specifically inhibiting TRPC4-containing channels might be effective to control fatal diseases such as sepsis where thrombin mediates the vicious cycle between inflammation and coagulation.Article信州医学雑誌 59(1): 13-26(2011)departmental bulletin pape