OBJECTIVETo investigate the effect of isopropyl 3-(3,4-dihydroxyphenyl)-2- hydroxypropanoate on vascular smooth muscle.

METHODIsolated rat pulmonary artery was perfused and the tension of the vessel was measured, the effect of isopropyl 3-(3, 4-dihydroxyphenyl)-2-hydroxypropanoate on the pulmonary artery precontracted by noradrenaline (NE) and concentration-response curves of 5-hydroxytryptamine (5-HT), endothelin-1 (ET-1), U46619 and KCl was also observed.

RESULTIsopropyl 3-(3,4-dihydroxyphenyl) -2-hydroxypropanoate exerted relaxation effect on the endothelium-intact artery precontracted by NE in a concentration-dependent manner, which was inhibited with denuded endothelium. The right-shift of the concentration-response curves of 5-HT, ET-1, U46619 and KCl.

CONCLUSIONIsopropyl 3-(3,4-dihydroxyphenyl)-2-hydroxypropanoate have relaxation action on rat pulmonary artery in the way of endothelium-dependance, the mechanism of relaxation action by isopropyl 3-(3,4-dihydroxyphenyl) -2-hydroxypropanoate may be related to calcium channels.

Animals ; Female ; In Vitro Techniques ; Male ; Muscle Contraction ; drug effects ; Muscle, Smooth, Vascular ; drug effects ; physiology ; Propionates ; pharmacology ; Pulmonary Artery ; drug effects ; physiology ; Rats ; Rats, Sprague-Dawley

AIMTo evaluate the relaxant effect of verapamil on human corpus cavernosum in vitro and to assess the drug's potential as a treatment for erectile dysfunction (ED).

METHODSPreparations of the human corpus cavernosum were obtained from recently deceased young men who had had normal erectile function. The isometric tension and detailed curves were recorded when contractions induced by 10 micromol/L phenylephrine were reduced by different doses of verapamil or the vehicle control (sterile water). The tension of human corpus cavernosum preparations are described as a percentage of their top tension before adding verapamil or the vehicle. ANOVA and least significant difference tests were used for statistical analysis.

RESULTSDoses of 1 micromol/L, 10 micromol/L and 100 micromol/L verapamil resulted in relaxation of (35.28+/-7.96)%, (55.91+/-6.41)%, (85.68+/-4.16)% after 30 min, respectively. The vehicle control at the same time point produced relaxation of (-0.06+/-10.57)% (P<0.05).

CONCLUSIONVerapamil is significantly effective in relaxing normal human corpus cavernous smooth muscle induced by phenylephrine in vitro and the relaxant effect depends on the concentration of verapamil.

Adult ; Humans ; In Vitro Techniques ; Male ; Muscle Relaxation ; drug effects ; Muscle, Smooth, Vascular ; drug effects ; physiology ; Penis ; drug effects ; physiology ; Verapamil ; pharmacology

Animals ; Aorta ; drug effects ; physiology ; Blood Pressure ; drug effects ; Cadmium ; toxicity ; Female ; In Vitro Techniques ; Male ; Muscle, Smooth, Vascular ; drug effects ; physiology ; Rabbits ; Vasoconstriction ; drug effects

AIMTo investigate the mechanisms of vasodilatation of plant-derived estrogen biochanin A.

METHODSIsolated aortic ring preparations from Sprague-Dawley rats were suspended in individual organ baths. The tension was measured isometrically.

RESULTSBiochanin A at the range of 10(-9)-10(-4) mol/L provoked concentration-dependent and endothelium-independent relaxation of the rings constricted by phenylephrine (10(-5) mol/L). Biochanin A caused concentration-dependent relaxation of denuded rings precontracted with KCl (6 x 10(-2) mol/L). Glibenclamide (3 x 10(-6) mol/L), a selective inhibitor of ATP-sensitive potassium channels, and tetraethylammonium (5 x 10(-3) mol/L), a Ca2+ -activated K+ channel inhibitor, significantly attenuated the relaxation induced by biochanin A. The vasoconstriction induced by phenylephrine was decreased by biochanin A in Ca2+ -free medium.

CONCLUSIONThe endothelium-independent relaxation of thoracic aorta induced by biochanin A might be mediated by ATP-sensitive K+ channels, Ca2+ -activated K+ channels and intracellular Ca2+ release from sarcoplasmic reticulum.

Animals ; Aorta, Thoracic ; drug effects ; physiology ; Genistein ; pharmacology ; In Vitro Techniques ; KATP Channels ; metabolism ; Male ; Muscle, Smooth, Vascular ; drug effects ; physiology ; Rats ; Rats, Sprague-Dawley ; Vasodilation ; drug effects

AIMTo study the effects of oxyphenamone (Oxy) on activation of Ca(2+)-activated K+ channels in rabbit mesenteric vascular smooth muscle cells.

METHODSTo measure the effect of Oxy on the Ca(2+)-activated K+ channel (BK (Ca) channel) activity in rabbit mesenteric vascular smooth muscle cells by using whole cell patch clamp techniques.

RESULTSOxy reversibly increase BK (Ca) channel activity in rabbit mesenteric artery smooth muscle cells. Application of Oxy (0.1 mumol.L-1) to the perfusion solution caused significant increase in outward currents and its effect was completely abolished by washout; The outward currents K+ was inhibited by TEA (7.5 mmol.L-1); Oxy activated the BK (Ca) channel in a dose-dependent manner (0.01-10 mumol.L-1).

CONCLUSIONOxy directly increase the activity of BK (Ca) channel activity in rabbit mesenteric vascular smooth muscle cells in dose-dependent manner.

Animals ; Cardiotonic Agents ; pharmacology ; Mesenteric Arteries ; cytology ; Muscle, Smooth, Vascular ; cytology ; Myocytes, Smooth Muscle ; physiology ; Organic Chemicals ; Patch-Clamp Techniques ; Potassium Channels, Calcium-Activated ; drug effects ; Rabbits

OBJECTIVETo explore the acute effects of testosterone at the physiological level on PGF2alpha-induced increase in intracellular Ca2+ in cultured vascular smooth muscle cells (VSMCs).

METHODSVSMCs from the thoracic aorta of male Sprague-Dawley rats were cultured using the explant method. The subconfluent VSMCs were incubated with serum-free medium for 24 hours to obtain quiescent non-dividing cells and then treated with the indicated agents. For the measurement of [Ca2+]i, the VSMCs were loaded with fura-2. Changes of [Ca2+]i were determined ratiometrically with a Nikon TE-2000E system.

RESULTSThe resting level of [Ca2+]i was around 100 nmol/L in the VSMCs. Exposing cells to perfusate containing 10 micromol/L PGF2alpha triggered an immediate and transient peak in [Ca2+]i, which gradually decreased afterwards. Interference at the peak with the physiological concentration (40 nmol/L) of testosterone significantly decreased the peak-to-baseline time of [Ca2+]i, compared with ethanol vehicle (104.9 +/- 27.0 s vs 153.5 +/- 40.4 s, P < 0.01). Pretreatment with testosterone at 40 nmol/L for 2 minutes also reduced the peak-to-baseline time of [Ca2+]i significantly in comparison with the ethanol control (120.6 +/- 32.0 s vs 151.4 +/- 27.4 s, P < 0.01), but it had no significant effect on the peak level of PGF2alpha-induced intracellular Ca2+ (390.0 +/- 126.0 nmol/L vs 403.4 +/- 160.7 nmol/L, P > 0.05).

CONCLUSIONTestosterone at physiological concentration inhibits PGF2alpha-induced Ca2+ fluxes, probably via receptor-operated calcium channels by a non-genomic mechanism in VSMCs, which may be involved in the vasodilatory effect of testosterone.

Animals ; Calcium ; metabolism ; Cells, Cultured ; Dinoprost ; pharmacology ; Male ; Muscle, Smooth, Vascular ; cytology ; drug effects ; Myocytes, Smooth Muscle ; metabolism ; Rats ; Rats, Sprague-Dawley ; Testosterone ; metabolism ; physiology

Retinoic acids may inhibit vascular smooth muscle cell proliferation, but may promote endothelial cell proliferation in cell culture. However, little data are available about the effects of all-trans-retinoic acid (ATRA) on endothelial regeneration and functional recovery in an experimental model of vascular injury. Accordingly, we investigated whether ATRA may attenuate neointima formation and accelerate endothelial regeneration with functional recovery in balloon-injured rat aorta. Twelve-week-old male Sprague-Dawley rats underwent endothelial denudation of the thoracic aorta by balloon injury. Fourteen rats were fed a standard rat pellet diet. Another 14 rats were fed ATRA (1.5 mg/day) for 2 weeks. The animals were killed on day 14 for organ chamber study and morphometric analysis. Rats in the ATRA group had a significantly improved acetylcholine-induced relaxation response than those in control group. However, endothelial independent response was not significantly different between the two groups. The extent of reendothelialization was markedly superior in the ATRA group compared with control group (p>0.05). Furthermore, neointima area and the ratio of neointima to medial area were significantly less in ATRA group than in control group (p>0.05). In conclusion, ATRA may accelerate endothelial regeneration with functional recovery, and attenuate neointima formation in balloon-injured rat aorta.
Acetylcholine/pharmacology ; Animal ; Aorta, Thoracic/physiology ; Aorta, Thoracic/injuries ; Aorta, Thoracic/drug effects* ; Balloon Dilatation/adverse effects ; Endothelium, Vascular/physiology ; Endothelium, Vascular/drug effects ; Male ; Muscle Relaxation/physiology ; Muscle Relaxation/drug effects ; Muscle, Smooth, Vascular/physiology ; Muscle, Smooth, Vascular/drug effects ; Rats ; Rats, Sprague-Dawley ; Regeneration/physiology ; Regeneration/drug effects ; Tretinoin/pharmacology* ; Tunica Intima/physiology ; Tunica Intima/pathology* ; Tunica Intima/drug effects* ; Vasodilator Agents/pharmacology

Chloride channels have been identified in vascular smooth muscle cells (SMCs). It has been shown that these channels are involved in myogenic tone regulation and neuromuscular transmission in various vascular beds. However, whether the chloride channels are responsible for the formation of excitatory junction potentials (EJPs) of SMCs in the spiral modiolar artery (SMA) remains unelucidated. In the present study, the effects of chloride channel blockers (niflumic acid, NFA; indanyloxyacetic acid 94, IAA-94; disodium 4, 4'-diisothiocyanatostilbene-2, 2'-disulfonate, DIDS) on EJP were explored in guinea pigs, using intracellular recording techniques on acutely isolated SMA. It was found that EJP was evoked in the majority of the SMCs (75%, n=49) with an adequate electronic stimulation. The amplitude of the EJP was partially blocked (30% approximately 80%) by combined application of alpha(1) receptor antagonist (prazosin) and alpha(2) receptor antagonist (idazoxan) at concentration of up to 1 micromol/L, and P(2x) receptor antagonist (PPADS, 10 approximately 100 micromol/L). NFA (100 micromol/L) could further inhibit the residual EJP in the presence of alpha(1), alpha(2)-adrenergic and P(2x) receptor antagonists. IAA-94 or DIDS not only inhibited the amplitude but also shortened the duration of EJP. Decrease of extracellular chloride concentration from 135.6 mmol/L to 60 mmol/L would enhance EJP. Moreover, IAA-94 (100 micromol/L) and DIDS (200 mumol/L) could reverse the enhancement of EJP by low extracellular Cl(-). NFA (100 micromol/L) could also block the residual depolarizations evoked by norepinephrine (NE, 1 approximately 50 micromol/L). Based on these results, it is inferred that NE could activate a novel adrenoceptor to open the chloride channel on the membrane of the SMCs, leading to a transmembrane Cl(-) current. This current is involved, at least partially, in the formation of EJP.
Adrenergic alpha-Antagonists ; pharmacology ; Animals ; Arteries ; physiology ; Chloride Channels ; antagonists & inhibitors ; Cochlea ; blood supply ; Excitatory Postsynaptic Potentials ; drug effects ; Female ; Guinea Pigs ; Male ; Muscle, Smooth, Vascular ; cytology ; physiology ; Myocytes, Smooth Muscle ; drug effects ; physiology ; Norepinephrine ; pharmacology

The purpose of the present study is to investigate the effect of isoliquiritigenin (ISL) on the cerebral basilar artery in spontaneously hypertensive rats (SHR). The change of SHR systolic pressure was measured by tail artery pressure measurement instrument before and after ISL intervention. After perfusion with 1 × 10(-5) mol/L phenylephrine (PE), 1 × 10(-5) mol/L PE + 1 × 10(-4) mol/L ISL and 1 × 10(-5) mol/L PE, the diameter of the cerebral basilar artery separated from SHR was measured by pressure myograph. The current of large-conductance calcium-activated potassium (BKCa) channel of SHR single vascular smooth muscle cell (VSMC) was recorded by whole-cell patch-clamp technique and the cGMP levels of basilar artery was evaluated by ELISA. The results showed that 1) after intervention with ISL for 14 days, the systolic pressure of SHR was decreased from (218.3 ± 1.6) mmHg to (119.2 ± 1.9) mmHg (P < 0.01), but there was no difference in systolic pressure between ISL-treated SHR and Wistar-Kyoto (WKY) rat; 2) 1 × 10(-4) mol/L ISL relaxed the SHR cerebral basilar artery (P < 0.01); 3) ISL significantly increased the outward current density of VSMC from SHR cerebral basilar artery (P < 0.01, n = 6), and the effect could be reversed by 1 × 10(-3) mol/L TEA (a BKCa channel inhibitor), but 3 × 10(-4) mol/L 4-AP (a Kv channel inhibitor) had no effect on the enhanced current density induced by ISL in VSMC; 4) 1 × 10(-5) mol/L Methylene blue (a sGC inhibitor) significantly inhibited the ISL-enhanced current density in VSMC (P < 0.05, n = 6); 5) ISL significantly increased the cGMP level of SHR basilar artery (P < 0.05, n = 6). The results suggest that the role of the ISL in relaxing the SHR cerebral basilar artery may be related to its effect in enhancing BKCa current by increasing the levels of cGMP in the VSMC.
Animals ; Basilar Artery ; drug effects ; Blood Pressure ; Cerebral Arteries ; drug effects ; Chalcones ; pharmacology ; Cyclic GMP ; physiology ; Muscle, Smooth, Vascular ; cytology ; Myocytes, Smooth Muscle ; physiology ; Patch-Clamp Techniques ; Potassium Channels, Calcium-Activated ; physiology ; Rats ; Rats, Inbred SHR ; Rats, Inbred WKY ; Systole

Isoproterenol (ISO), a beta agonist, causes hyperpolarization of coronary smooth muscle cells via an increase in K+ conductance. This hyperpolarization may cause the coronary vasorelaxation by decreasing the cytoplasmic Ca2+ concentration. It is well known that the activation of beta adrenoreceptors stimulates the adenylate cyclase activity, and the resulting K+ channel phosphorylation by cAMP-dependent protein kinase may be responsible for ISO-induced increase in K+ channel activity. However, it is not clear whether the increase in K+ channel activity by ISO is exclusively due to the activation of adenylate cyclase or not. In this research, the effect of ISO on the isometric tension and the mechanism of ISO-induced K+ channel activation were investigated in various patch clamp conditions. The summarized results are as follows. ISO- and pinacidil induced vasorelaxation was significantly inhibited by the application of TEA or by increasing the external K+ concentration. In the whole cell clamp mode, application of ISO increased K+ outward current, and this effect was completely eliminated by propranolol. In the cell-attached patch, application of ISO or forskolin increased Ca(2+)-activated K+ channel activity. Application of ISO to the bath in the outside-out patches or GTP in the inside-out patches stimulated Ca(2+)-activated K+ channels. From the above results, both A-kinase dependent channel phosphorylation and direct GTP-binding protein mediated effect might be responsible for the the activation of Ca(2+)-activated K+ channel by ISO in rabbit coronary smooth muscle cells. And this K+ channel activation also contributes to the ISO-induced vasorelaxation.
Animal ; Calcium/*metabolism ; Coronary Vessels/*drug effects/physiology ; Cyclic AMP-Dependent Protein Kinases/physiology ; Female ; GTP-Binding Proteins/physiology ; Isoproterenol/*pharmacology ; Male ; Muscle, Smooth, Vascular/*drug effects/physiology ; Potassium Channels/*drug effects ; Rabbits ; Support, Non-U.S. Gov't ; Vasodilation/drug effects