Mastoparan-7 activates guanine nucleotide-binding proteins (G-proteins) and stimulates both apoptosis and increases in cytoplasmic calcium concentration and may induce smooth muscle contraction. The primary aim of the present study was to evaluate the modulatory effect of laser stimulation on vascular smooth muscle contraction induced by direct stimulation of G-protein with mastoparan-7. Experiments were performed on isolated and perfused tail arteries of Wistar rats. Contraction force in the model was measured by increased levels of perfusion pressure with a constant flow. Irradiation treatment was applied directly to the blood vessels. The laser was applied in increasing doses of 10 mW (E=1.8 J), 30 mW (E=5.5 J) and 110 mW (E=19.8 J). Time of exposure was 3 min for each irradiation. In the laser-stimulated arteries, a significant and dose-dependent decrease was observed. The half maximal effective concentration values were 4.43±2.2x10-8, 2.4±0.56x10-7, 3.2±0.72x10-7 and 7.7±0.3x10-7 M/l in the control and 10, 30 and 110 mW laser irradiation groups, respectively. Significant (P<0.001) changes were identified for all laser treatment groups in comparison with the control. When analyzing the function of calcium ion (Ca2+) stores was analyzed, a significant inhibition of influx from both intra- and extracellular Ca2+ stores was observed. The results from the present study suggested that contraction induced by direct activation of G-protein with mastoparan-7 may by effectively inhibited by laser radiation, and that the effect was associated with an inhibition of Ca2+ influx from both intracellular and extracellular Ca2+ stores.
Keywords: guanine nucleotide-binding protein; low-level laser irradiation; mastoparan-7; phospholipase C.
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