A Comparative Study On Reactivities Of Rat Arterioles To Vasoconstrictors

Objectives:Observe the differences in contractile reactivities of rat arterioles isolated fromfive kinds of organs to depolarization, potassium channel blockers and thromboxaneA2(TxA2) analog U46619; and explored the endothelium mechanisms involved inU46619-induced contraction.Methods:1: Vitro arteriole rings experimental procedures. Rats were killed by cervicaldislocation and exsanguinated, removed heart, brain, kidney, lung and small intestineand placed into4℃PSS immediately. Slightly isolated coronary arterioles, middlecerebral arterioles, the second branch of intrarenal arterioles, the third branch ofintrapulmonary arterioles, and mesenteric arterioles under integrated microscope.Then fixed arterioles on the sensor of vitro microvascular tension tester, recorded thechanges of vascular tone to vasoconstrictors by Powerlab Chart.2: Statistical analysis. Using One-Way ANOVA with post-hoc muitiplecomparisons to investigate the differences of reactivities among rat arterioles tovasoconstrictors, and using t test to explore the endothelial mechanisms underlyingU46619-induced contraction. Results:1: Gradiently increased potassium ion concentration of extracellularenvironment (20,40,60,80mM) enhanced the basal tone of rat arteriolescumulatively, and the reactivities of rat arterioles to KCl (40,60,80mM) presenttissue differences. The EC50values are: coronary arterioles (47.0±9.6) mM, middlecerebral arterioles(56.2±7.8) mM, intrarenal arterioles (40.2±0.1) mM,intrapulmonary arterioles(40.4±0.5) mM and mesenteric arterioles (56.4±7.8) mM.2: TEA(10mM) obviously contracted rat coronary, middle cerebral, intrarenalarterioles; slightly contracted rat mesenteric and intrapulmonary arterioles; and thereactivities of rat arterioles to TEA (10mM) present tissue differences (P<0.01). Thecontractile percentages of TEA are: coronary arterioles (151.6±18.2)%, middlecerebral arterioles (114.7±7.9)%, intrarenal arterioles(65.4±38.4)%, intrapulmonaryarterioles (1.2±1.0)%and mesenteric arterioles(0.7±0.2)%.3: BaCl2(1mM) obviously contracted rat coronary, middle cerebral, intrarenal,intrapulmonary and mesenteric arterioles; the reactivities of rat arterioles toBaCl2(1mM) present tissue differences (P<0.01). The contractile percentages ofBaCl2are: coronary arterioles (102.7±22.6)%, middle cerebral arterioles(71.6±6.7)%, intrarenal arterioles (36.6±16.6)%, intrapulmonary arterioles(46.9±6.0)%and mesenteric arterioles (12.7±6.8)%.4:4-AP (1mM) obviously contracted rat middle cerebral arterioles; slightlycontracted rat coronary, intrarenal, intrapulmonary and mesenteric arterioles; thereactivities of rat arterioles to4-aminopyridine (1mM) present tissue differences(P<0.01).The contractile percentages of4-AP are: coronary arterioles (3.2±0.4)%,middle cerebral arterioles (119.2±19.1)%, intrarenal arterioles (1.8±2.1)%,intrapulmonary arterioles (2.5±1.9)%and mesenteric arterioles (0.2±0.2)%.5: Glibenclamide (0.01mM) obviously contracted rat middle cerebral andcoronary arterioles; slightly contracted rat intrarenal, intrapulmonary and mesenteric arterioles; the reactivities of rat arterioles to glibenclamide (0.01mM) present tissuedifferences (P<0.01).The contractile percentages of glibenclamide are: coronaryarterioles (36.6±32.2)%, middle cerebral arterioles (76.1±27.2)%, intrarenalarterioles(3.4±5.0)%, intrapulmonary arterioles (1.0±0.8)%and mesenteric arterioles(0.5±0.5)%.6: U46619concentration-dependently contracted rat arterioles, and thecontractility of U46619(0.1,1μM) presents tissue differences (P<0.01). Incubatednitric oxide synthase inhibitor L-NAME(0.1mM)enhanced the contractility ofU46619on rat coronary, middle cerebral, intrarenal and intrapulmonary arterioles;incubated cyclooxygenase inhibitor indomethacin(0.01mM) decreased thecontractility of U46619on rat intrarenal and mesenteric arterioles. The EC50valuesare: coronary arterioles (3.1±1.1) mM, middle cerebral arterioles(4.7±8.1) μM,intrarenal arterioles (1.66±2.44) μM, intrapulmonary arterioles (2.08±1.35) μM andmesenteric arterioles (0.6±0.7) mM.Conclusions:1: The reactivities of rat arterioles to potassium ion channel blockers anddepolarization present tissue differences.2: U46619concentration-dependently contracted rat arterioles, and thecontractility of U46619(0.1,1μM) presents tissue differences, NO and prostaglandinsinvolved in the contraction of U46619.