Vasodilatory effect of midazolam on pre-contractions of in-vitro porcine coronary artery and its mechanisms / 中国药理学通报

Aim To investigate the effects of midazolam on porcine isolated coronary artery rings pre-contracted by potassium chloride(KCl)and the possible mechanism.Methods The vessel tension recorder system was used.Isotonic tension of porcine isolated coronary artery rings precontracted by KCl(30 mmol·L-1)was recorded.The vasorelaxing action of midazolam and effects of various drugs were observed in the rings.Results Midazolam(3×10-6～1×10-4 mol·L-1)respectively concentration-dependently reduced the contraction induced by KCl,and there was significant difference between the rings with intact and denude endothelium(P<0.05).On KCl-induced precontraction,midazolam′s relaxation was depressed by L-NAME and the blend of L-NAME and L-Arg(P<0.05),but was not affected by Indo,L-Arg and 1400W.The contraction was not prevented by pretreatment with the inhibitor of Na+/Ca2+ exchanger(KB-R7943).The inhibitor of KATP(Gli)restrained the diastolic function of midazolam(P<0.05),while the inhibitor of BKCa(TEA),Kir(BaCl2),KV(4-AP)had no obvious effect.Conclusions Midazolam produces remarkable vasodilatation on KCl pre-contracted porcine isolated coronary artery rings.Its relaxtion effect is via concentration-dependent and endothelium-dependent mechanisms and relevant to the production of NO.Na+/Ca2+ exchanger is not involved midazolam′s vasodilatation on KCl pre-contracted porcine coronary artery rings.The relaxant mechanism of midazolam may be concerned with KATP.The Kir,BKCa and KV may be not involved.

The relaxing effect of Poncirus fructus and its flavonoid content on porcine coronary artery / 한국실험동물학회지

Coronary artery disease is a common occurrence in human, and causes enormous social cost. Poncirus fructus (PF), the dried immature fruits of Poncirus trifoliata Rafinesquem, is used in the treatment of womb contraction and dyspepsia, as a prokinetic, and in improving blood circulation. This study was performed to investigate the effects of PF and some of its flavonoids components on the coronary from the pig. The arterial ring was suspended by a pair of stainless steel stirrups in an organ bath. The end of the upper stirrup was connected to an isometric force transducer. A dose-dependent induction of relaxation was observed by both water and 70% ethanol extracts of PF in the porcine coronary artery precontracted with U46619 (100 nM), a stable analogue of the potent vasoconstrictor thromboxane A2. The 70% ethanol extract showed more efficacy than the water extract. Pretreatment of the artery with L-NAME (100 microM), a nitric oxide synthase inhibitor, resulted in a significant reduction in the relaxation induced by PF extract. In addition, ODQ (10 microM), a soluble guanylate cyclase inhibitor, also significantly reduced the effects of PF extracts. Hesperidin, a flavonoid present in PF, induced very weak relaxation of the porcine coronary artery at a high concentration (100 microM), while its aglycone, hesperetin, demonstrated a dose-dependent relaxation. In conclusion, PF extracts induced relaxation in the porcine coronary artery, partially through the nitric oxide-cGMP pathway, and the aglycones of flavonoids might be also involved in the relaxation of the same artery.

Effects of caffeine and ryanodine on K_(Ca) in porcine coronary artery smooth muscle cells / 中国病理生理杂志

AIM: To study the effect of caffeine on the large conductance calcium activated potassium (K_(Ca)) channels by patch-clamp technique on smooth muscle cells enzymatically isolated from the porcine coronary artery (PCASMC),and to investigate the effect of ryanodine on K_(Ca) being activated by caffeine.METHODS: Using the single channel patch-clamp technique,single PCASMC was isolated by collagenase,the activity of single K_(Ca) channel was recorded in porcine coronary artery smooth muscle cells.RESULTS: Caffeine (0.1-10 mmol/L) enhanced the open probability (Po) of K_(Ca) channels in a dose-dependent manner in the intracellular side of inside-out patches and its effect was almost completely abolished by washout. Caffeine decreased the mean close time markedly,but had no effect on the amplitude of K_(Ca) channels. However,ryanodine (10-40 μmol/L) decreased Po of K_(Ca) channels activated by caffeine in a dose-dependent manner in cell-attached patches. The mean open time also decreased.CONCLUSION: Caffeine directly activates K_(Ca) channels of porcine coronary artery smooth muscle cells in inside-out patches,the activity of single K_(Ca) channel is inhibited by ryanodine indirectly in cell-attached patches.

The Effects of Etomidate on the Isolated Porcine Coronary Artery / 대한마취과학회지

BACKGROUND: Etomidate produces minimal cardiovascular effects in clinical uses but their effects on the porcine coronary arteries are not well known yet. We studied the direct effects of etomidate on porcine coronary arterial tone and the underlying mechanism of its vascular relaxation. METHODS: Porcine coronary arterial ring segments (3-4 mm) with or without endothelium were suspended in modified Krebs solution (37oC) and preconstricted with K+ 40 mM. Changes in tension were measured following cumulative administrations of etomidate (10(-5), 5 x 10(-5) and 10(-4) M). Relaxation caused by etomidate (10(-4)M) were measured in the presence of either NG-nitro-L-arginine methyl ether (L-NAME 10(-5)M, n = 13), indomethacin (2.8 x 10(-5)M, n = 12), methylene blue (2 x 10(-5)M, n = 12), tetraethylammonium (TEA, KCa2+ blocker, 20 mM, n = 11), glibenclamide (n = 13) 2.5 x 10(-5)M or 4-aminopyridine (4-AP, K+ DR blocker, 10 4 M, n = 12). Effects of etomidate on Ca2+ influx through the voltage operated channel (VOC) of the vascular cells were also evaluated. RESULTS: Arterial reings were relaxed by etomidate in a concentration-dependent manner and these effects were not affected by endothelium. In the etomidate pretreated group, arterial ring in a calcium-free solution showed no contraction with KCl 40 mM, but the contraction after the administration of calcium 2.5 mM less than without etomidate group (47.2 +/- 8.7% vs 97.7 +/- 10.6%). The other group, not pretreated with etomidate, showed the same vascular tone of the control group in a slow upstroke manner with calcium administration. Pretreatment with either L-NAME, indomethacin and methylene blue did not affect etomidate-induced vasorelaxation. The TEA, glibenclamide and 4-AP pretreated groups also did not affect the vascular relaxation. CONCLUSIONS: Etomidate relaxes the porcine coronary artery in a concentration-dependent manner withor without endothelium, via inhibition of Ca2+ influx through the voltage-operated Ca2+ channel.

The preventive effects of the heparin-coated coronary stent in a porcine coronary stent restenosis model / 대한내과학회지

BACKGROUND: The coronary stent reduces acute coronary arterial occlusion and late restenosis during and after coronary intervention. However, stent thrombosis and restenosis are still major limitations in widespread use of coronary stent. Local drug delivery with use of heparin-coated stent will be a new approach reducing the incidence of stent thrombosis and restenosis. In order to evaluate the effects of heparin-coated stent on stent restenosis, heparin-coated stents were compared with control stents in a porcine coronary stent restenosis model. METHODS: Stent overdilation injury (stent:artery= 1.3:1.0) was performed with bare Wiktor (Group I, n=10) and heparin-coated Wiktor (Group II, n=20) stents (HEPAMEDTM, Medtronics, U.S.A.) in porcine coronary arteries. Follow-up quantitative coronary angiography (QCA) was performed at 4 weeks after stenting and histopathologic assessments of stented porcine coronary arteries were compared in both groups. RESULTS: 1) On QCA, percent diameter stenosis was significantly higher in Group I than in Group II (16.3+/-6.62% vs. 9.6+/-5.06%, p<0.05). 2) Injury score of stented porcine coronary artery was not different in both groups (1.26+/-0.23 vs. 1.20+/-0.22). 3) Pathologic area stenosis of stented artery was higher in Group I than in Group II (41.6+/-12.5% vs. 27.1+/-9.9%, p<0.005). 4) Neointimal area was higher in Group I than in Group II (4.58+/-1.41 mm2 vs. 2.57+/-1.07 mm2, p<0.05). 5) By immunohistochemistry, proliferating cell nuclear antigen (PCNA) index was higher in Group I compared with in Group II (11.2+/-6.75% vs. 6.3+/-4.14%, p<0.05). CONCLUSIONS: Heparin-coated stent is effective in the prevention of late coronary stent restenosis in a porcine coronary stent restenosis model, which may be related with the inhibition of neointimal cell proliferation.

Effects of calcium channel blockers on porcine cardiac and coronary arterial function in ischemia-reperfusion

This study was designed to investigate effects of calcium antagonists on endothelial and neuronal dysfunction of right coronary artery (RCA) induced by ischemia- reperfusion in anesthetized, open-chest pigs. After reperfusion, pigs were sacrificed and the RCA was rapidly dissected for in vitro experiments. Experimental groups were divided into 4 groups: control (C-RCA), ischemia-reperfusion only (I-RCA), verapamil infusion (VI-RCA) and nifedipine infusion (NI-RCA) group, respectively. The ischemia did not affect hemodynamics, mean arterial pressure, heart rate, LVdP/dtmax, and decreased RCA flow. Arterial pressure and heart rate during ischemia-reperfusion were decreased in VI-RCA and NI-RCA, and RCA flow during reperfusion was increased in NI-RCA. 5-Hydroxytryptamine (5-HT) produced concentration-dependent contractions in C-RCA. The 5-HT-induced contractions were potentiated in I-RCA and VI-RCA, but not in NI-RCA. Endothelium-dependent relaxation by calcium ionophore A23187 was inhibited in I-RCA and VI-RCA, and recovered in NI-RCA. Cyclic GMP contents were decreased in I-RCA group alone. Electrical field stimulation in C-RCA produced transient and frequency-dependent contractions and at 50 Hz caused biphasic contractions. The transient contractions were not affected by pretreatment with phentolamine and atropine, but the biphasic contraction was altered by the pretreatment. Both contractions were inhibited in I-RCA, and were partially recovered in VI-RCA and NI-RCA. Ischemia-reperfusion of RCA in pigs causes endothelial and neuronal dysfunctions, and calcium antagonists partially prevent both.

Effects of Ketamine on the Ca(2+) Channel and K(+) Channel of the Porcine Coronary Artery / 대한마취과학회지

BACKGROUND: Ketamine produces increasing in heart rate and arterial blood pressure, in vivo. However, the direct effects of ketamine itself on the porcine coronary arteries are not well determined. In this study, the direct effects of ketamine on the porcine coronary artery responses to vasoactive agents that operate through Ca2+ channel, K+ channels and endothelium related mechanisms were investigated, in vitro. METHODS: Adult porcine hearts(n=12) were obtained from a slaughter house. Coronary arteries were perfused and dissected with 4oC Krebs solution, and were cut into vessel rings and prepared with and without the endothelium(3~4mm in length). The ring segments were suspended in tissue bath(5ml) filled with Krebs solution at 37oC and bubbled with 95% O2-5% CO2 gas mixture. The effect of ketamine(5 10 5, 10 4, 2 10 4M) on vascular smooth muscle tone caused by Ca2+[voltage operated channel(VOC), receptor operated channel(ROC)] and K+channels(Ca2+activated K+ currents, ATP-sensitive K+ currents) regulation were studied with Ca2+ free solution and K+channel blocker. RESULTS: Ketamine induced vasorelaxation of porcine coronary rings that were precontracted by KCl(50 mM) or acetylcholine(3 10 7M). The changes of vascular tone in endothelium intact and removed group did not show statistical significance. In ketamine pretreated group(Ca2+ free solution), after ketamine pretreatment, the last vascular tone was same as that relaxed by ketamine. The other group that without pretreatment of ketamine, the last vascular tone was same as that precontracted with KCl or acetylcholine. In the TEA pretreated group, the porcine coronary artery relaxation was reversed. However, pretreatment with glybenclamide, the porcine coronary artery relaxation was not reversed. CONCLUSIONS: Ketamine induced vasorelaxation of the porcine coronary artery as concentration relating manner, in vitro. The vasorelaxation induced by ketamine was not associated with endothelium. Furthermore, an antagonism of Ca2+ channels(VOC, ROC) and activation of Ca2+ activated K+ channels may be responsible for the porcine coronary arterial relaxing effect of ketamine.

Effect of 17beta-estradiol on the Contraction to Endothelin-1 in Porcine Coronary Artery / 대한내과학회지

OBJECTIVES: It is widely accepted that estrogen has favorable effects on cardiovascular diseases, especially in the postmenopausal women. Endothelin-1(ET-I), released from the vascular endothelium, is a 21-amino acid peptide with strong vasoconstrictor activity. However, the effect of estrogen on the vasoconstriction to ET-1 has not been extensively studied. METHODS: To investigate the effect of estrogen (175beta-estradiol) on the vascular contraction to ET-1, porcine coronary artery(PCA) rings were suspended in organ chambers(37 degrees C, 95% O2/5% CO2) for measurement of isometric tension change. Endothelium was removed mechanically if necessary. In acute experiments, vascular rings were preincubated for 15minutes with 3different concentrations of 170beta-estradiol(10(-6), 10(-5), 10(-4)M) and concentration-contraction curves to cumulative doses of ET-1 were constructed. In the experiments after a longer exposure to 17beta-estradiol, the vessels with endothelium were exposed in the 5% CO2 incubator to 3different concentrations of 17beta-estradiol(10(-9), 10(-8), 10(-7)M) for 44-50 hours, and then concentrationcontraction curves to ET-1 were obtained. RESULTS: Incubation for 15minutes with 170beta-estradiol(10(-4)M) inhibited ET-1-induced contraction in the vessels with endothelium(area under the curve and maximal contraction, p<0.05 compared with control). This effect persisted regardless of the sex and the presence or absence of the endotheliurn. Incubation of the vessels far a longer time with 170beta-estradiol(44-50 hours) resulted in the inhibition of maximal contraction to ET-1(p<0.05) by a lower concentration of 175beta-estradiol(10(-7)M) than in acute experiments in male PCA rings, but an enhanced contraction to ET-1(area under the curve; p<0.05) by 10M of 175beta-estradiol was observed in female PCA rings. CONCLUSION: Short-time incubation with 17Pbeta-estradiol has an inhibitory effect on the contraction to ET-1 in PCA rings. This effect is independent of the presence of the endothelium and the sex of the pigs. A longer incubation with 17beta-estradiol results in a similar inhibitory effect on male(but not female) PCA rings, suggesting that a sex-related difference may exist concerning the effect of 17beta-estradiol on ET-1-induced contraction.

Potentiating Effects of Bay K 8644 on the Relaxation Induced by Ultraviolet or Visible Light in Porcine Coronary Artery

BACKGROUND: This study was aimed at defining the varying responses of porcine coronary artery(PCA) to various wavelengths of ultraviolet irradiation, and at relating them to the changes in cyclic GMP contents. METHODS: The ring preparations of PCA with intact or removed endothelium were irradiated with the ultraviolet or visible light of wavelengths(240-520mm) from xenon lamp of a spectrofluorometer, and the changes in vascular tension were recorder on polygraph. For cyclic GMP assay, rat thoracic aorta was frozen after irradiation and homogenated. The supernatant was extracted with water-saturated ether and the cyclic GMP contents were measured with radioimmunoassay. RESULTS: Ultraviolet irradiation relaxed the preparations(UVR-relaxation) in resting state and those precontracted by prostaglandin F2alpha, the maximal relaxation occurring at 410nm, and the magnitude depending on the duration of irradiation. The UVR-relaxation was not affected by removing the endothelium, while it was markedly potentiated by pretreatment with Bay K 8644. The Bay K 8644-induced potentiation of UVR-relaxation was abolished by hemoglobin and slightly reduced by wrapping the rings with aluminum foil. Cyclic GMP contents in the increase was markedly potentiated by pretreatment with Bay K 8644. CONCLUSION: The observations suggest that UVR-relaxation in procine coronary artery is caused by activating the nitric oxide-cyclic GMP system, which is most sensitively activated by UVR of 410nm and that its potentiation induced by Bay K 8644 may be related nitrous substance released from the agent upon UVR.

Contractile and Inhibitory Effects of McN-A-343 and Acetylcholine on Isolated Arteries

Effect of acetylcholine(ACh) and McN-A-343 on porcine coronary artery and rabbit thoracic aorta were investigated in isolated preparations with or without intact endothelium. In the porcine coronary artery, ACh produced concentration dependent contraction which was greater in rings without the endothelium than in intact endothelial rings, but McN-A-343 did not alter the basel tension in both tissues. ACh relaxed contraction induced by 5-hydroxytryptamine(5-HT) in only intact endothelial rings, while NcN-A-343 inhibited the 5-HT induced tension in both preparations dose dependently. Carbachol elicited a prominent contraction in both tissues. The carbacol-induced tension was markedly inhibited by McN-A-343 in either rings with or without endothelium, while ACh contracted further the tension. ACh and McN-A-343 did not after the KCi induced tension, but clearly potentiated the contraction induced by Bay K 8644 in intact endothelial rings. In rabbit thoracic aorta, ACh elicited contraction in a concentration-dependent fashion which was potentiated by removal of endothelium, but McN-A-343 did not affect the basal tension of both rings. ACh inhibited the 5-HT-induced contraction in only intact endothelial ring, but McN-A-343 did not change the contraction of both rings. Conclusively, ACh produces endothelium-dependent relaxation in both arteries, while McN-A-343 elevated endothelium-independent inhibition to 5-HT or carbachol-induced tension.

Effects of caffeine and ryanodine on KCa in porcine coronary artery smooth muscle cells / 中国病理生理杂志

AIM:To study the effect of caffeine on the large conductance calcium activated potassium (KCa) channels by patch-clamp technique on smooth muscle cells enzymatically isolated from the porcine coronary artery (PCASMC),and to investigate the effect of ryanodine on KCa being activated by caffeine.METHODS:Using the single channel patch-clamp technique,single PCASMC was isolated by collagenase,the activity of single KCa channel was recorded in porcine coronary artery smooth muscle cells.RESULTS:Caffeine (0.1-10 mmol/L) enhanced the open probability (Po) of KCa channels in a dose-dependent manner in the intracellular side of inside-out patches and its effect was almost completely abolished by washout. Caffeine decreased the mean close time markedly,but had no effect on the amplitude of KCa channels. However,ryanodine (10-40 ?mol/L) decreased Po of KCa channels activated by caffeine in a dose-dependent manner in cell-attached patches. The mean open time also decreased.CONCLUSION:Caffeine directly activates KCa channels of porcine coronary artery smooth muscle cells in inside-out patches,the activity of single KCa channel is inhibited by ryanodine indirectly in cell-attached patches.