thapsigargin and 2-(4-amylcinnamoyl)amino-4-chlorobenzoic-acid

The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor simvastatin is able to produce endothelium-dependent relaxation in addition to its lipid-lowering properties. The underlying mechanisms were investigated in bovine aortic endothelial cells (BAEC). Simvastatin induced an increase in cytosolic calcium ([Ca(2+)](i)) in BAEC, by releasing Ca(2+) from intracellular stores sensitive to thapsigargin and ryanodine, and increasing Ca(2+) entry. Simvastatin response was not altered by the phospholipase A(2) inhibitor ONO-RS-082, or the combination of superoxide dismutase plus catalase. However, the response to simvastatin was reduced by the product of HMG-CoA reductase, mevalonate or by the inhibitor of small G proteins of the Rho family, Clostridium botulinum C3 toxin. Thus, increase in [Ca(2+)](i) involving the activation of Rho protein through mevalonate-dependent pathway is essential for the action of simvastatin and might contribute to its beneficial effects against vascular diseases. This study helps elucidate the mechanisms of endothelial factor generation by simvastatin in BAEC.

Topics: Aminobenzoates; Animals; Aorta; Botulinum Toxins; Bradykinin; Calcium; Calcium Signaling; Catalase; Cattle; Cells, Cultured; Chlorobenzoates; Cinnamates; Endothelium, Vascular; Free Radical Scavengers; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Mevalonic Acid; ortho-Aminobenzoates; Phospholipases A; rho GTP-Binding Proteins; Ryanodine; Simvastatin; Superoxide Dismutase; Superoxides; Thapsigargin

The origin of Ca2+ necessary for carbachol (CCh)-induced contraction of longitudinal muscle of the proximal colon of rats was studied. CCh induced contraction of the muscle consisting of two phases, phasic and tonic phases, with a concomitant biphasic increase in [Ca2+]i. After removal of Ca2+ from the bathing solution of the colonic segments, CCh-induced contraction was rapidly inhibited; there was almost complete inhibition 1 min after the removal. Nicardipine, a blocker of voltage-dependent calcium channel, also significantly inhibited CCh-induced contraction. On the other hand, treatment of the colonic segments with thapsigargin, an inhibitor of sarcoplasmic reticulum (SR) Ca2+-ATPase, did not significantly affect the contraction except causing a slight decrease in the rate of contraction. These results suggest that Ca> entering through voltage-dependent calcium channels, but not released from SR, is essential for CCh-induced contraction of longitudinal muscle of the proximal colon of rats. This strict dependency of the CCh-induced contraction on extracellular Ca2+ was discussed in relation to the results obtained in the fundus of rats.

Topics: Aminobenzoates; Animals; Caffeine; Calcium; Calcium Channel Blockers; Carbachol; Chlorobenzoates; Cinnamates; Colon; Enzyme Inhibitors; Gastrointestinal Motility; Male; Muscle Contraction; Muscle, Smooth; Nicardipine; ortho-Aminobenzoates; Parasympathomimetics; Phosphodiesterase Inhibitors; Rats; Rats, Wistar; Sarcoplasmic Reticulum; Thapsigargin