Lidocaine and pinacidil added to blood versus crystalloid cardioplegic solutions: study in isolated hearts

Abstract Objective: The present study aimed the functional recovery evaluation after long term of cardiac arrest induced by Custodiol (crystalloid-based) versus del Nido (blood-based) solutions, both added lidocaine and pinacidil as cardioplegic agents. Experiments were performed in isolated rat heart perfusion models. Methods: Male rat heart perfusions, according to Langendorff technique, were induced to cause 3 hours of cardiac arrest with a single dose. The hearts were assigned to one of the following three groups: (I) control; (II) Custodiol-LP; and (III) del Nido-LP. They were evaluated after ischemia throughout 90 minutes of reperfusion. Left ventricular contractility function was reported as percentage of recovery, expressed by developed pressure, maximum dP/dt, minimum dP/dt, and rate pressure product variables. In addition, coronary resistance and myocardial injury marker by alpha-fodrin degradation were also evaluated. Results: At 90 minutes of reperfusion, both solutions had superior left ventricular contractile recovery function than the control group. Del Nido-LP was superior to Custodiol-LP in maximum dP/dt (46%±8 vs. 67%±7, P<0.05) and minimum dP/dt (31%±4 vs. 51%±9, P<0.05) variables. Coronary resistance was lower in del Nido-LP group than in Custodiol-LP (395%±50 vs. 307%±13, P<0.05), as well as alpha-fodrin degradation, with lower levels in del Nido-LP group (P<0.05). Conclusion: Del Nido-LP cardioplegia showed higher functional recovery after 3 hours of ischemia. The analysis of alpha-fodrin degradation showed del Nido-LP solution provided greater protection against myocardial ischemia and reperfusion (IR) in this experimental model.

Effects of Lubiprostone on Pacemaker Activity of Interstitial Cells of Cajal from the Mouse Colon

Lubiprostone is a chloride (Cl-) channel activator derived from prostaglandin E1 and used for managing constipation. In addition, lubiprostone affects the activity of gastrointestinal smooth muscles. Interstitial cells of Cajal (ICCs) are pacemaker cells that generate slow-wave activity in smooth muscles. We studied the effects of lubiprostone on the pacemaker potentials of colonic ICCs. We used the whole-cell patch-clamp technique to determine the pacemaker activity in cultured colonic ICCs obtained from mice. Lubiprostone hyperpolarized the membrane and inhibited the generation of pacemaker potentials. Prostanoid EP1, EP2, EP3, and EP4 antagonists (SC-19220, PF-04418948, 6-methoxypyridine-2-boronc acid N-phenyldiethanolamine ester, and GW627368, respectively) did not block the response to lubiprostone. L-NG-nitroarginine methyl ester (L-NAME, an inhibitor of nitric oxide synthase) and 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ, an inhibitor of guanylate cyclase) did not block the response to lubiprostone. In addition, tetraethylammonium (TEA, a voltage-dependent potassium [K+] channel blocker) and apamin (a calcium [Ca2+]-dependent K+ channel blocker) did not block the response to lubiprostone. However, glibenclamide (an ATP-sensitive K+ channel blocker) blocked the response to lubiprostone. Similar to lubiprostone, pinacidil (an opener of ATP-sensitive K+ channel) hyperpolarized the membrane and inhibited the generation of pacemaker potentials, and these effects were inhibited by glibenclamide. These results suggest that lubiprostone can modulate the pacemaker potentials of colonic ICCs via activation of ATP-sensitive K+ channel through a prostanoid EP receptor-independent mechanism.

Protective effects of pinacidil hyperpolarizing cardioplegia on myocardial ischemia reperfusion injury by mitochondrial KATP channels / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Many studies have indicated that hyperpolarizing cardioplegia is responsible for myocardial preservation and researchers have suggested that the adenosine triphosphate-sensitive potassium channels (K(ATP)) were the end effectors of cardio-protection. But whether mitochondrial K(ATP) plays an important role in hyperpolarizing cardioplegia is not apparent. The present study investigated the effect of hyperpolarizing cardioplegia containing pinacidil (a nonselective K(ATP) opener) on ischemia/reperfusion injury in rat hearts, especially the role of mitochondrial K(ATP) in pinacidil hyperpolarizing cardioplegia.</p><p><b>METHODS</b>Sprague-Dawley rat hearts were Langendorff-perfused for 20 minutes with Krebs-Henseleit buffer at 37°C before equilibration. Cardiac arrest was then induced in different treatments: there was no arrest and ischemia in the normal group, the control group were arrested by clamping the aorta, depolarizing caidioplegia (St. Thomas solution containing 16 mmol/L KCl) and hyperpolarizing cardioplegia groups used St. Thomas solution containing 0.05 mmol/L pinacidil and 5 mmol/L KCl to induce cardiac arrest in group hyperkalemic and group pinacidil, in group hyperkalemic + 5-hydroxydecanote (5HD) and Pinacidil + 5HD, 5HD (0.1 mmol/L) was added to the above two solutions to block mitochondria K(ATP) channels. Global ischemia was then administrated for 40 minutes at 37°C, followed by 30 minutes of reperfusion. At the end of equilibration and reperfusion, hemodynamics, ultrastructure, and mitochondrial function were measured.</p><p><b>RESULTS</b>In the control group, ischemia/reperfusion decreased the left ventricular developed pressure, heart rate, coronary flow, mitochondrial membrane potential, impaired mitochondrial respiratory function, increased reactive oxygen species and left ventricular end diastolic pressure. Damage to myocardial ultrastructure was also evident. Both depolarized arrest and especially hyperpolarized cardioplegia significantly reduced these lesions. 5HD partially blocked the beneficial effects of pinacidil cardioplegia but showing no effects on hyperkalemic arrest.</p><p><b>CONCLUSIONS</b>Pinacidil cardioplegia provides better cardioprotection with preservation of hemodynamics, ultrastructure, and mitochondrial function than traditional cardioplegia. The mitochondria K(ATP) channels may play an important role in the protection mechanism.</p>

The Role of Oxygen-Derived Free Radicals in Vascular Relaxations to Pinacidil in Renal Hypertensive Rats / 대한신장학회지

PURPOSE: Evidence has emerged that oxygen-derived free radicals may induce vascular relaxations via ATP-sensitive K+ (K(ATP)) channels and the level of free radicals is increased in animal models of hypertension. The present study was conducted to determine whether relaxations to an K(ATP) channel opener, pinacidil, are increased in the aorta from two-kidney, one clip (2K1C) hypertensive rats and whether free radial scavengers reduce these relaxations. METHODS: 2K1C hypertension was induced by clipping the left renal artery and age-matched control rats received a sham treatment. Rings of aortae without endothelium were suspended for isometric force recording. RESULTS: Relaxations to pinacidil (10(-8) to 10(-5) M), which are abolished by glibenclamide (10(-5) M), were augmented in the aorta from 2K1C rats, compared to those from control rats. In the aorta from 2K1C rats, catalase (1,200 U/mL), but neither superoxide dismutase (150 U/mL) nor deferoxamine (10(-4) M), reduced relaxations to pinacidil, whereas in the aorta from control rats, the free radical scavengers did not affect these relaxations. CONCLUSION: These results suggest that in 2K1C hypertension, vasorelaxation to an KATP channel opener is augmented and that hydrogen peroxide in smooth muscle cells may partly contribute to these relaxations.

The Influences of G Proteins, Ca2+, and K+ Channels on Electrical Field Stimulation in Cat Esophageal Smooth Muscle

NO released by myenteric neurons controls the off contraction induced by electrical field stimulation (EFS) in distal esophageal smooth muscle, but in the presence of nitric oxide synthase (NOS) inhibitor, L-NAME, contraction by EFS occurs at the same time. The authors investigated the intracellular signaling pathways related with G protein and ionic channel EFS-induced contraction using cat esophageal muscles. EFS-induced contractions were significantly suppressed by tetrodotoxin (1 micrometer) and atropine (1 micrometer). Furthermore, nimodipine inhibited both on and off contractions by EFS in a concentration dependent meaner. The characteristics of 'on' and 'off' contraction and the effects of G-proteins, phospholipase, and K+ channel on EFS-induced contraction in smooth muscle were also investigated. Pertussis toxin (PTX, a Gi inactivator) attenuated both EFS-induced contractions. Cholera toxin (CTX, Gs inactivator) also decreased the amplitudes of EFS-induced off and on contractions. However, phospholipase inhibitors did not affect these contractions. Pinacidil (a K+ channel opener) decreased these contractions, and tetraethylammonium (TEA, K+ Ca channel blocker) increased them. These results suggest that EFS-induced on and off contractions can be mediated by the activations Gi or Gs proteins, and that L-type Ca2+ channel may be activated by G-protein alpha subunits. Furthermore, K+ Ca-channel involve in the depolarization of esophageal smooth muscle. Further studies are required to characterize the physiological regulation of Ca2+ channel and to investigate the effects of other K+ channels on EFS-induced on and off contractions.

The Effects of Ethanol and Acetaldehyde on Corpus Cavernosal Smooth Muscle of the Rabbit / 대한남성과학회지

PURPOSE: This study is to assess the pharmacologic effects of ethanol and its metabolite, acetaldehyde on potassium channels of the corpus cavernosal smooth muscle of the rabbit. MATERIALS AND METHODS: Cavernosal strips from New Zealand white rabbits were harvested and pharmacophysiologic organ bath studies were executed. In equilibrium state after incubation, zaprinast (PDE5 inhibitor) induced relaxations were monitored in strips precontracted with phenylephrine (PE, 10(-4)M). The inhibitory effects of ethanol and acetaldehyde (2, 20, 40, 80 mmol) on zaprinast-induced relaxations were recorded. Pinacidil (K(ATP) channel opener) and phloretin (BK channel opener) were tested to reverse the inhibitory effects of ethanol and acetaldehyde on zaprinast-induced relaxations. RESULTS: Both ethanol and acetaldehyde inhibited the zaprinast-induced relaxations in a dosedependent manner (p<0.05). Both pinacidil and phloretin abolished the inhibition by both ethanol and acetaldehyde (p<0.05). Ethanol and acetaldehyde inhibits cavernosal relaxation, possibly through BK channels and K(ATP) channels. CONCLUSIONS: These results suggest that ethanol and its metabolite may affect the corpus cavernosal smooth muscle directly and lead to consequent erectile dysfunction. Furthermolecular and electrophysiological studies will help reveal the underlying mechanisms to which this process occurs.

Effect of KATP channel openers on myogenic and neurogenic responses in goat urinary bladder.

Isolated goat detrusor muscle exhibited spontaneous contractility with an irregular amplitude and frequency. The spontaneity of detrusor muscle exhibited a mean amplitude as 11.99 +/- 0.83 mm and frequency as 1.37 +/- 0.16/min. KATP-channel openers namely, cromakalim or pinacidil (10(-7) - 10(-4) M) added cumulatively, elicited a concentration-related inhibition of both amplitude and rate of spontaneous contractions. The mean IC50 values for both amplitude and frequency for cromakalim were 3.3 x 10(-6) M and 2.9 x 10(-6) M, respectively; and for pinacidil were 2.0 x 10(-5) M and 1.5 x 10(-5) M, respectively. Glibenclamide, a KATP-channel blocker inhibited the cromakalim-induced concentration-related relaxation of spontaneous contractions with a significant increase in its mean IC50. ACh-induced concentration-related contractile response was inhibited in the presence of either cromakalim (10(-4) M) or pinacidil (10(-4) M). The mean EC50 value of ACh, in the presence of cromakalim (2.5 x 10(-3) M) was significantly increased as compared to the control (1.2 x 10(-6) M). In the presence of glibenclamide (10(-5) M) the inhibitory effect of cromakalim was significantly reduced with consequent decrease in the EC50 value (1.9 x 10(-5) M). Application of EFS (30 V and 5 ms) on goat urinary bladder strips at 1, 2, 5, 10, 20 and 30 Hz elicited frequency-related contractile responses. Both cromakalim and pinacidil caused a rightward shift in the frequency-related contractile response curve with significant increase in the mean EF25 and EF50 values, respectively. In the presence of glibenclamide (10(-4) M), the frequency-related inhibitory response curve was shifted to left with significant (P < 0.001) increase in the mean EF25, EF50 and EF75. The present results suggest that in the goat detrusor muscle, agonist and EFS-induced contractile responses were more potently inhibited by cromakalim than pinacidil with activation of glibenclamide sensitive KATP channels.

Pinacidil reduces neuronal apoptosis following cerebral ischemia-reperfusion in rats through both mitochondrial and death-receptor signal pathways / 神经科学通报·英文版

<p><b>OBJECTIVE</b>To investigate effect of pinacidil, an ATP sensitive potassium channel (K(ATP)) opener, on the neuronal apoptosis and its signaling transduction mechanism following focal cerebral ischemia-reperfusion in rats.</p><p><b>METHODS</b>One hundred male Wistar rats were randomly divided into four groups: A, sham-operated group; B, ischemia-reperfusion group; C, K(ATP) opener treatment group; and D, K(ATP) opener and blocker treatment group. The middle cerebral artery occlusion (MCAO) model was established by using the intraluminal suture occlusion method, neuronal apoptosis was determined by TUNEL staining, and expressions of caspase-8, caspase-9 and caspase-3 mRNA were detected by in situ hybridization.</p><p><b>RESULTS</b>(1) The numbers of apoptotic neurons at 12 h, 24 h, 48 h, and 72 h were significantly less in group C than in groups B and D (P< 0.01 or P< 0.05); and there was no difference between groups B and D at all time points (P> 0.05). (2) The expressions of caspase-3 mRNA and caspase-8 mRNA at all times and the expressions of caspase-9 mRNA at 12 h, 24 h, 48 h, 72 h were significantly lower in group C than in groups B and D (P< 0.01 or P< 0.05); and there were no differences between groups B and D at all time points (P> 0.05).</p><p><b>CONCLUSIONS</b>K(ATP) opener can significantly decrease the neuronal apoptosis and the expressions of caspase-3, caspase-8 and caspase-9 mRNAs following cerebral ischemia-reperfusion. The neuronal apoptosis may be decreased by the inhibition of both mitochondrial and death-receptor signal pathways.</p>

Inhibition of Pacemaker Activity of Interstitial Cells of Cajal by Hydrogen Peroxide via Activating ATP-sensitive K(+) Channels

To investigate whether hydrogen peroxide (H2O2) affects intestinal motility, pacemaker currents and membrane potential were recorded in cultured interstitial cells of Cajal (ICC) from murine small intestine by using a whole-cell patch clamp. In whole cell patch technique at 30 degress C, ICC generated spontaneous pacemaker potential under current clamp mode (I=0) and inward currents (pacemaker currents) under voltage clamp mode at a holding potential of -70 mV. When ICC were treated with H2O2 in ICC, H2O2 hyperpolarized the membrane potential under currents clamp mode and decreased both the frequency and amplitude of pacemaker currents and increased the resting currents in outward direction under voltage clamp mode. Also, H2O2 inhibited the pacemaker currents in a dose-dependent manner. Because the properties of H2O2 action on pacemaker currents were same as the effects of pinacidil (ATP-sensitive K+ channels opener), we tested the effects of glibenclamide (ATP-sensitive K+ channels blocker) on H2O2 action in ICC, and found that the effects of H2O2 on pacemaker currents were blocked by co- or pre-treatment of glibenclamide. These results suggest that H2O2 inhibits pacemaker currents of ICC by activating ATP-sensitive K(+) channels.

Involvement of potassium channels in hypoglycemic effect of sertraline.

Effect of 21 days administration of sertraline (30 mg/kg, po) in streptozotocin (55 mg/kg, ip) induced diabetic and non-diabetic rats produced hypoglycemia in diabetic and non-diabetic rats. Pinacidil (1mg/kg, po), when co-administered with sertraline or glimepiride antagonized the decrease in glucose levels in diabetic rats. Pinacidil (10(-6)-10(-3) M) produced dose dependent relaxation (EC50-1.58 x 10(-5) M). Neither sertraline nor glimepiride had any effect on the resting tension of ileum preparation. Both sertraline and glimepiride antagonized competitively the pinacidil-induced relaxation. The pA2 values of sertraline and glimepiride reversal of pinacidil-induced relaxation were 5.5 and 6.2 respectively. These studies suggest the involvement of K+ channels in hypoglyceimic effects of sertraline.

The Effects of Ischemic Preconditioning and K(ATP) channel Activation on the Expression of the PKC-epsilon, NF-kappaB and AP-1 in Ischemia-reperfused Rat Heart / 체질인류학회지

This study was aimed to elucidate the effects of K(ATP) activation during IPC on the PKC-epsilon, NF-kappaB and AP-1 in ischemia-reperfused rat hearts. SD male rats weighting from 300 to 350 g were split into 9 groups, such as sham control (S), IPC, 3 cycles of 5 min ischemia and 5 min reperfusion, continuous preconditioning (CP), 8 cycles of 5 min ischemia and 5 min reperfusion, K(ATP) opening (KO) with pinacidil (1.0 mg/kg), K(ATP) blocking with glibenclamide (1.0 mg/kg) injection, ischemia (IS), 30 min ischemia, IPC followed by IS, 8) K(ATP) blocking and IPC followed by IS (KB+IPC+IS), IS and K(ATP) opening (KO+IS). Heart were subjected to ligation of left descending coronary artery and reperfusion in groups of IPC, CP, IS with or without IPC. Immunohistochemistry and Western blotting for PKC-epsilon, NF-kappaB and AP-1 were performed at 3, 6, 24 hours after reperfusion or treatment. Immunoreactivities against PKC-epsilon antibody were observed stronger in the groups of IPC, KO, IPC+IS and KO+IS than groups of KB, IS and KB+IPC+IS. NF-kappaB activation and translocation were only observed in the groups of including 30 min ischemia and reperfusion. AP-1 activation and translocation were opposite to the results of PKC-epsilon activation. In the group of CP, KB, IS and KB+IPC+IS, reactivities of AP-1 antibody were stronger than IPC+IS, KO+IS, and weaker in the groups of S, IPC and KO. These results suggest that K(ATP) opening with IPC or pharmacological methods may direct effect on the PKC-epsilon activation and that K(ATP) blocking has effect on the AP-1 activation and translocation in the heart of ischemiareperfused of rats.

Effects of calcium channel blocker, mibefradil, and potassium channel opener, pinacidil, on the contractile response of mid-pregnant goat myometrium.

The present study was undertaken to investigate the in vitro influence of mibefradil, a calcium channel blocker, and pinacidil, a potassium channel opener, on pregnant goat myometrial spontaneous rhythmic contractility and contractions induced with the agonist, oxytocin. Longitudinal strips from the distal region of uterus, collected from goats at midgestation, were mounted in an organ bath for recording isometric contractions. Mibefradil (10(-8)-10(-4) M) or pinacidil (10(-10)-10(-4) M), added cumulatively to the bath at an increment of 1 log unit, caused concentration-dependent inhibition of the spontaneous rhythmic contractions of isolated uterine strips. The rhythmic contraction was, respectively, abolished at 100 and 10 microM concentrations of mibefradil and pinacidil. In a concentration-dependent manner, mibefradil (1 and 10 microM) antagonized the contractions elicited with oxytocin (10(-5)-10(-2) IU). Pretreatment of uterine strips with glibenclamide (10 microM), a selective KATP channel blocker, caused a rightward shift of the concentration-response curve of pinacidil with a concomitant decrease in its pD2 value. Pinacidil (0.3, 1 and 3 microM), in a concentration-related manner, antagonized the oxytocin (10(-5)-10(-2) IU)-induced contractile response. The inhibition of spontaneous rhythmic contractions and antagonism of oxytocin-induced contraction by mibefradil in the pregnant goat myometrium may be related to the antagonism of voltage-dependent Ca2+ channels, while by pinacidil suggests that KATP channel could be a therapeutic target for tocolysis.

Effects of iptakalim on intracellular calcium concentrations, PKA and PKC activities in rat tail artery smooth muscle cells / 药学学报

<p><b>AIM</b>To investigate the effects of iptakalim, a new structural potassium channel opener (KCO), on intracellular calcium concentration ([Ca2+]i), protein kinase C (PKC), and cAMP-dependent kinase (PKA) activities in rat tail artery smooth muscle cells (RTA-SMC), and to analyze mechanisms involved in iptakalim reversing hypertensive vascular remodeling.</p><p><b>METHODS</b>RTA-SMC was cultured and passages 3-4 were used for experiment. [Ca2+] i was measured by laser scanning confocal microscope after loaded with fluorescent indicator fluo-3-acetoxymethylester, and activities of PKA and PKC were detected by commercial assay kits (the nonradioactive PepTag system) following instructions.</p><p><b>RESULTS</b>Compared with baseline, [Ca2+] i reduced significantly after iptakalim- or pinacidil-treatment at concentrations of 0.1, 1 and 10 micromol x L(-1), while diazoxide caused significant decrease at concentration of 1 and 10 micromol x L(-1). After preincubation with 1 micromol x L(-1) glibenclamide, [Ca2+] i was not significantly changed when iptakalim, pinacidil or diazoxide were added at concentration of 0.1 and 1 micromol x L(-1). Activities of PKA and PKC increased significantly by 1 micromol x L(-1) iptakalim- or pinacidil-treatment, while 1 micromol x L(-1) diazoxide induced significant change in activity of PKC but not in that of PKA.</p><p><b>CONCLUSION</b>The characteristics of iptakalim on [Ca2+] i, PKA and PKC are more or less similar to those of pinacidil. Iptakalim decreased [Ca2+] i while increased PKA and PKC activities of RTA-SMCs, which may contribute to its ability to reverse antihypertensive vascular remodeling.</p>

Effects of quinidine on pinacidil-induced transmural dispersion of repolarization in canine right ventricular wall / 中华心血管病杂志

<p><b>OBJECTIVE</b>On the basis that pinacidil can produce an "all or none" repolarization in right ventricular wall of canine, to observe the effects of quinidine on the marked transmural dispersion of repolarization. Recent studies have shown that ventricular myocardium is composed of at least 3 electrophysiological distinct cell types: epicardial, endocardial, and midcardial cells. Differences in the response of the 3 cell types to pharmacologic agents and/or pathophysiological states often result in amplification of intrinsic electrical heterogeneities, thus providing a substrate as well as a trigger for the development of arrhythmias. The study was designed to observe the right ventricular transmural heterogeneity in vitro canine heart tissue preparation level.</p><p><b>METHODS</b>The strips were isolated from the anterior wall of the right ventricular of canine. The preparations perfused with oxygenated (95%O(2)/5%CO(2)) Tyrode's solution. The tissues were stimulated at basic cycle lengths of 1000 ms. Standard microelectrode techniques were used. Transmembrane action potentials were recorded from epicardial, midcardial and endocardial cells respectively from right ventricular free wall of canine on different conditions [perusing with Tyrode's solution (Control), pinacidil (2.5 micromol/L), and quinidine (5 micromol/L) in turn].</p><p><b>RESULTS</b>Compared with that of endocardial cells, the action potentials of canine ventricular epicardial and midcardial cells had more obvious spike and dome morphology. Pinacidil (2.5 micromol/L) caused a loss of the dome of transmembrane action potentials and a marked abbreviation of the action potential duration (APD) in right ventricular epicardial and midcardial cells, especially in epicardial cells, but not in endocardial cells (n = 10). With pinacidil (2.5 micromol/L), in epicardial cells, phase 2 amplitude of action potentials decreased from (117.7 +/- 9.3) mV to (71.3 +/- 6.4) mV (P < 0.01), and 90% of the APD(90) decreased from (198.2 +/- 20.8) ms to (103.9 +/- 13.5) ms (P < 0.01). The transmural dispersion of action potential duration increased from (48.5 +/- 9.2) ms to (128.7 +/- 13.5) ms (P < 0.01). Quinidine (5 micromol/L) effectively prolonged the APD abbreviated by pinacidil, restored or partly restored the dome of transmembrane action potentials of epicardial and midcardial cells but not of endocardial cells (n = 10). In epicardial cells phase 2 amplitude increased from (71.3 +/- 6.4) mV to (106.6 +/- 7.7) mV (P < 0.01), and 90% of the APD(90) increased from (103.9 +/- 13.5) ms to (185.9 +/- 15.7) ms (P < 0.01). The transmural dispersion of action potential duration significantly decreased from (128.7 +/- 13.5) ms to (54.3 +/- 10.8) ms (P < 0.01). Quinidine reduced pinacidil-induced transmural dispersion of phase 2 amplitude and the APD in right ventricular wall of canine.</p><p><b>CONCLUSION</b>By restoring the dome and the APD of the epicardial and midcardial cells action potentials, quinidine (5 micromol/L) could reduce the marked transmural dispersion of repolarization caused by pinacidil.</p>

Influence of pinacidil on the myocardial mitochondrial structure and the respiratory function in scalded rats / 中华烧伤杂志

<p><b>OBJECTIVE</b>To investigate the influence of pinacidil preconditioning on the protection of the structure and respiratory function of injured myocardial mitochondria in scalded rats.</p><p><b>METHODS</b>Seventy-five healthy Wistar rats, weighed 250 approximately 300 g, were randomly divided into three groups: i.e. control (n = 9, with intraperitoneal injection of 50 microg/kg isotonic saline), scald (n = 33, with 30% TBSA full thickness scald) and pre-conditioning (n = 33, with same extent of scald injury after intraperitoneal injection of 50 microg/kg pinacidil) groups. Mitochondrial ultrastructure was observed by transmission electron microscope. The mitochondrial respiratory function, the MDA content and the superoxide anion level were determined with corresponding methods.</p><p><b>RESULTS</b>The degree of injury to rat myocardial mitochondria in pre-conditioning group was less intensive than that in scald group (P < 0.05 or 0.01). The respiratory control rate in pre-conditioning group was obviously higher than that in scald group (P < 0.05), and the contents of MDA and superoxide anion in pre-conditioning group were markedly lower than those in scald group (P < 0.05 or 0.01), as evidenced by their contents at 3 post scalding hours (0.60 +/- 0.09 micromol/g and 0.127 +/- 0.020) were obviously lower than those in scald group (0.83 +/- 0.07 micromol/g and 0.169 +/- 0.015) (P < 0.01).</p><p><b>CONCLUSION</b>Pinacidil preconditioning was beneficial in the protection of myocardial mitochondria in scalded rats, and it might be related to the pre-opening of potassium channel which was sensitive to mitochondrial ATP.</p>

Regulatory effects of nucleotides on ATP-sensitive potassium channel opener pinacidil-induced vascular relaxation / 中国应用生理学杂志

<p><b>AIM</b>In order to evaluate the regulatory effects of nucleotides and adenosine on ATP-sensitive potassium channel (K(ATP)) in artery smooth muscles, the effects of them on vascular relaxation induced by K(ATP) opener pinacidil(Pin) were investigated.</p><p><b>METHODS</b>The isolated endothelium- denuded aorta rings were preincubated with nucleotides or nucleotides and glibenclamide (Gli) for 10 min, the vascular relaxation induced by Pin in aorta precontracted with 20 mmol x L(-1) KCl was observed.</p><p><b>RESULTS</b>After the isolated endothelium-denuded aorta rings were preincubated with ATP, ADP, UDP, GTP and adenosine (Ade) 100 micromol x L(-1) respectively, the vascular relaxation induced by Pin was changed as following: (1) ATP could inhibit the K(ATP) activation by Pin and enhance the blockade of K(ATP) by Gli. (2) ADP could inhibit the K(ATP) activation by Pin and attenuate the blockade of K(ATP) by Gli. (3) The regulatory effect of Ade on K(ATP) was similar with that of ADP. (4) UDP could enhance the K(ATP) activation by Pin and attenuate the blockade of K(ATP) by Gli. (5) GTP could enhance the K(ATP) activation by Pin, but had no effects on the blockade of K(ATP) by Gli.</p><p><b>CONCLUSION</b>Nucleotides and adenosine, related to energy metabolism, could modulate the functions of K(ATP) in vascular smooth muscle. But their pharmacological characteristics were different.</p>

Iptakalim enhances astrocytic glutamate uptake activity / 药学学报

<p><b>AIM</b>To investigate the effect of iptakalim (Ipt), a novel ATP-sensitive potassium channel opener (KATPCO), on astrocyte glutamate uptake activity. The mechanism of action involved was also examined.</p><p><b>METHODS</b>Primary cultures of astrocytes were prepared from cerebral cortexes of 1 to 2 days old Sprague-Dawley rats. Cultures were preincubated with iptakalim of various concentrations with the absence or presence of 6-hydroxydopamine (6-OHDA, 50 micromol x L(-1)). Then, the cells were treated with pinacidil (10 micromol x L(-1), K+ channel opener) instead of iptakalim and pretreated with glibenclamide (20 micromol x L(-1), ATP-sensitive K+ channel inhibitor) before pinacidil or iptakalim was added into the medium so that the mechanism of action of iptakalim could be analysed. Astrocyte glutamate uptake activity was determined by intracellular concentration of 3H labeled D,L-glutamate, using isotope techniques.</p><p><b>RESULTS</b>Both iptakalim and pinacidil were shown to increase glutamate uptake activity of astrocytes and reverse inhibitory effect induced by 6-OHDA. But the increased and reversed effects of iptakalim or pinacidil on astrocytic glutamate uptake were found to be completely antagonized by glibenclamide.</p><p><b>CONCLUSION</b>These data indicated that iptakalim can enhance astrocytic glutamate uptake activity due to its K+ channel opening properties and lessen glutamate excitotoxicity. Iptakalim may be useful for the therapy of Parkinson's disease.</p>

Effect of pinacidil on rat myocardial calcium regulation / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To understand the effect of pinacidil on rat myocardial Ca(2+)regulation.</p><p><b>METHODS</b>After baseline measurement and a period of equilibrium, myocytes were randomly allocated to one of 4 treatment groups: Control group (8 myocytes): incubation in Lactate Ringer's solution at 24 degrees C for 2 hours; K group (8 myocytes): incubation in Lactate Ringer's solution containing 16 mmol/L potassium at 24 degrees C for 2 hours; K+P group (8 myocytes): incubation in Lactate Ringer's solution containing potassium 16 mmol/L and pinacidil 50 micromol/L at 24 degrees C for 2 hours; K+P+G group (8 myocytes): incubation in Lactate Ringer's solution containing potassium 16 mmol/L, pinacidil 50 micromol/L and glibenclamide 10 micromol/L at 24 degrees C for 2 hours. After each incubation, myocytes were resuspended in cell culture media at the same temperature and intracellular [Ca(2+)](i) and SR Ca(2+) release were measured.</p><p><b>RESULTS</b>The amplitude percent of [Ca(2+)](i) transient evoked by electrical stimulation in the K group was significantly decreased to 67.05% - 80.11% compared to 90.27% - 95.57% in the K+P group during reperfusion after ischemia (P<0.01). The percent amplitude of the [Ca(2+)](i) transient evoked by the rapid application of 10 mmol caffeine in the K group myocyte was approximately 112.00%+/-16.93% compared with that of the [Ca(2+)](i) transient evoked by electrical stimulation. However, in the K+P group myocyte the peak amplitude of the caffeine induced Ca(2+) release was 173.15%+/-26.01% compared with electrical stimulation (P<0.01). The duration of transient evoked by caffeine in K+P group (3.20+/-0.71 ms was significantly shorter than that in K group (3.93+/-0.46) ms (P<0.05).</p><p><b>CONCLUSION</b>Cardioplegic arrest with simultaneous activation of KATP channels preserves rat myocardial Ca2+ by inducing sarcoplasmic reticulum Ca(2+) release and by alteration of Na(+)-Ca(2+) exchanger to better maintain [Ca(2+)](i) homeostasis.</p>