S(+)-ketamine, but not R(-)-ketamine, reduces postischemic adherence of neutrophils in the coronary system of isolated guinea pig hearts.

Polymorphonuclear neutrophils (PMN) play a crucial role in the initiation of reperfusion injury. In a previous study, we found that ketamine reduced the postischemic adherence of PMN to the intact coronary system of isolated guinea pig hearts. Because ketamine is a racemic mixture (1:1) of two optical enantiomers, we looked for possible differences in action between the stereoisomers. Seventy-six guinea pig hearts were perfused in the "Langendorff" mode under conditions of constant flow (5 mL/min) using modified Krebs-Henseleit buffer. After 15 min of global warm ischemia, freshly isolated human PMN (10(6)) were infused as a bolus into the coronary system during the second minute of reperfusion. PMN adhesion was expressed as the numeric difference between PMN recovered in the effluent and those applied. Series A hearts received 5 microM S(+), 5 microM R(-), or 10 microM racemic ketamine starting 20 min before ischemia and during reperfusion. In Series B hearts, 10 microM nitro-L-arginine, an inhibitor of NO synthase, was added to the perfusate. In Series C, PMN were preincubated for 15 min with 5 microM S(+)- or R(-)-ketamine. Coronary vascular leak was assessed by measuring the rate of formation of transudate on the epicardial surface. Ischemia/reperfusion without anesthetics increased coronary PMN adherence from 25.5% +/-2.3% (basal) to 35.3%+/-1.5% of the number applied. S(+)-ketamine reduced postischemic adherence in each series (A, 25.5%+/-5.1%; B, 22.5%+/-1.7%; C, 25.3%+/-7.7%), as did racemate (A, 26.4%+/-3.7%). Although 5 microM R(-)-ketamine had no effect on adhesion (A, 30.5%+/-6.7%; B, 34.3%+/-5.1%; C, 34.3%+/-4.3%), it significantly increased vascular leak in the presence of NOLAG. These findings indicate stereoselective differences in biological action between the two ketamine isomers: S(+)-ketamine inhibited PMN adherence, R(-)-ketamine worsened coronary vascular leak in reperfused isolated hearts. IMPLICATIONS: In this study, we demonstrated stereoselective differences in the biologic action of the two ketamine isomers in an animal model of myocardial ischemia. Polymorphonuclear neutrophil adherence to the coronary vasculature after ischemia was inhibited by S(+)-ketamine, whereas R(-)-ketamine increased coronary vascular fluid leak.     

The relaxant effect of propofol on guinea pig tracheal muscle is independent of airway epithelial function and beta-adrenoceptor activity.

Airway epithelium and vascular endothelium modulate the tension of the underlying smooth muscle by releasing relaxing factors such as prostanoids and nitric oxide (NO). We investigated whether the relaxant effect of propofol on airway smooth muscle is dependent on airway epithelial function. Tracheal spirals of female guinea pigs were mounted in water-jacketed organ baths filled with Krebs-bicarbonate buffer aerated with 95% O2 and 5% CO2 at 37 degrees C. Changes in isometric tension of the specimens were measured with a force-displacement transducer and recorded with a polygraph. Propofol (10(-4) to 10(-3) M) inhibited carbachol (CCh)-, histamine (HA)-, or endothelin-1-induced contractions of the muscles in a dose-dependent manner. Neither mechanical removal of the epithelial layer, chemical inhibition of epithelial synthesis of prostanoids, nor NO affected the relaxant effect of propofol on CCh- or HA-induced tracheal contraction. Furthermore, the blockade of beta-adrenoceptors did not change the relaxant effect of propofol. These results indicate that the relaxant effect of propofol on the airway smooth muscle is independent of the epithelial function or beta-adrenoceptor activity. Propofol is an excellent anesthetic for patients with hyperreactive airways in which the epithelial layer is damaged. IMPLICATIONS: Airway epithelium, as well as vascular endothelium, plays an important role in modulating the baseline tone and reactivity of underlying smooth muscle. We investigated, in vitro, whether the relaxant effect of propofol on airway smooth muscle is dependent on airway epithelial function. We suggest that propofol relaxes airway smooth muscle independently of the epithelial function.     

Bradykinin B2, but not B1, receptor antagonism has a neuroprotective effect after brain injury.

The aim of the present study was to measure the therapeutic effects of bradykinin antagonists on lesion volume and brain swelling induced by cold injury in the parietal cortex of rat and mouse, respectively. Cold lesion was induced by application of a precooled (-78 degrees C) copper cylinder (3 mm diameter) to the intact dura of rat and mouse for 6 and 30 sec, respectively. At 24 h after the injury, the brains were removed and lesion volume was determined by the triphenyltetrazolium chloride method in rats. In the mouse, brain swelling was expressed as percentage increase in weight of the injured hemisphere which is compared to the contralateral side. After a subcutaneous priming dose of 18 microg/kg, a 1-h pretreatment and 24-h posttreatment using osmotic minipumps (300 ng/kg x min) was applied. Hoe140, a bradykinin receptor 2 antagonist, revealed a 19% reduction of lesion volume (p < 0.05) in the rat and a 14% diminution of brain swelling (p < 0.05) in the mouse. In contrast, the bradykinin receptor 1 antagonist, B 9858, had no effect on lesion volume compared to sham treated rats. When B 9858 was given in combination with Hoe140, a significant reduction in lesion volume was seen which was equivalent to and not different from that seen with Hoe140 alone in the rat. We conclude that brain injury after cold lesion is partially mediated by bradykinin and can be successfully treated with B2 antagonists.     

The potency of KUL-7211, a selective ureteral relaxant, in isolated canine ureter: comparison with various spasmolytics

We compared the potency of a selective ureteral relaxant KUL-7211 (₂/₃-adrenoceptor agonist; (-)-2-[4-(2-{[(1S,2R)-2-hydroxy-2-(4-hydroxyphenyl)-1-methylethyl]amino}ethyl)phenyloxy]acetic acid) with those of various spasmolytics on contractions in isolated canine ureteral preparations. Drug effects were evaluated on the tonic contraction induced by KCl (80 mM) and on spontaneous, 1×10^–5 M phenylephrine-, and 1×10^–6 M PGF₂-induced rhythmic contractions in isolated canine ureteral preparations using a functional experimental technique. The potencies (pD₂ value) of the following drugs were compared: KUL-7211, tamsulosin (an _1A/1D-adrenoceptor antagonist), prazosin (an ₁-adrenoceptor antagonist), verapamil (a Ca²⁺-channel blocker), butylscopolamine (a nonselective muscarinic antagonist), and papaverine (a phosphodiesterase inhibitor). The rank order of relaxing potencies against KCl-induced tonic contraction was KUL-7211 (6.60)>tamsulosin(5.90)>verapamil(5.70)>papaverine(4.88)>prazosin (4.54). The rank order of potencies for reductions in spontaneous rhythmic contractions was KUL-7211 (6.80)>verapamil(6.12)>papaverine(5.05). Conversely, high concentrations of the two -adrenoceptor antagonists (tamsulosin and prazosin) and of butylscopolamine enhanced the spontaneous contractions, although at low concentrations (up to 1×10^–6 M) they had no significant effects. For suppression of spasmogen-induced rhythmic contractions, the rank order of potencies was, against phenylephrine-induced contractions: KUL-7211 (6.95)>tamsulosin(6.26)>prazosin(5.68)>verapamil(5.64)>papaverine (5.03), and against PGF₂-induced contractions: KUL-7211 (7.05)>verapamil(6.70)>papaverine (5.27). Our results suggest that in dogs, the ₂/₃-adrenoceptor agonist KUL-7211 is the most efficacious ureteral relaxant among the spasmolytics tested against various contractions. Possibly, KUL-7211 might be useful for promoting stone passage and relieving ureteral colic in urolithiasis patients.     

Direct comparative effects of isoflurane and desflurane in isolated guinea pig hearts.

The aim of this study was to test if myocardial and coronary vascular effects of desflurane and isoflurane were similar in the isolated heart. The cardiac effects of these anesthetics were examined in 12 guinea pig hearts perfused in a retrograde manner. Spontaneous heart rate, atrioventricular (AV) conduction time, systolic left ventricular pressure and coronary flow were measured. To differentiate direct vasodilatory effects of these anesthetics from an indirect metabolic effect due to autoregulation of coronary flow, O2 delivery (DO2), myocardial O2 consumption (MVO2) and percent O2 extraction were also monitored. Isoflurane and desflurane were injected directly into sealed bottles containing oxygenated perfusate solution. Each heart was perfused randomly with these anesthetics. Anesthetic concentrations in the perfusate were 0.28 +/- 0.02 and 0.52 +/- 0.02 mM for isoflurane and 0.59 +/- 0.01 and 1.02 +/- 0.09 mM for desflurane (mean +/- standard error of the mean). Calculated vapor concentrations were 1.3 and 2.5 vol % for isoflurane and 6.8 and 11.8 vol % for desflurane which correspond to approximately 1 and 2 MAC in vivo. Each anesthetic similarly decreased heart rate and prolonged AV conduction time in a concentration-dependent manner. Left ventricular pressure (control 93 +/- 4 mmHg) decreased by 11 +/- 1% and 24 +/- 2% with isoflurane and by 15 +/- 1% and 30 +/- 2% with desflurane. The decreases in heart rate and pressure were accompanied by decreases in MVO2 of 12 +/- 2% and 30 +/- 3% with isoflurane and of 19 +/- 3% and 40 +/- 4% with desflurane from a control of 57 +/- 2 microliters.g-1.min-1.(ABSTRACT TRUNCATED AT 250 WORDS)     

Albumin is required for the guinea pig sperm capacitation but is not essential for acrosome reaction and fusion with eggs.

The importance of serum albumin in supporting guinea pig sperm capacitation, acrosome reaction, and fusion with eggs in vitro was studied by incubating the spermatozoa in albumin-free medium containing different synthetic polymers. Serum albumin was found to be an obligatory component in the incubating medium for the capacitation of guinea pig spermatozoa. Albumin in the medium is not essential for the acrosome reaction and fusion with the eggs, but these phenomena take place most efficiently in presence of albumin.     

Airway response to salbutamol: effect of regular salbutamol inhalations in normal, atopic, and asthmatic subjects.

This study was designed to determine whether resistance to the airway effects of the beta-agonist, salbutamol, would develop in three groups of subjects while taking large doses of inhaled salbutamol. Six normal non-atopic, six atopic non-asthmatic, and eight atopic asthmatic subjects were studied by an identical technique. The development of resistance was assessed from salbutamol dose-response studies in which the airway response was measured as specific airway conductance (sGaw). Further evidence was sought in the atopic and asthmatic subjects by measuring the airway response to a standard histamine inhalation challenge and the protective effect of 100 micrograms salbutamol on this challenge, and by six-hourly peak flow recordings. Subjects were assessed before and during four weeks in which they took inhaled salbutamol regularly in doses increasing to 500 microgram quid in week 4. Normal subjects showed a progressive reduction in the bronchodilator (sGaw) response to salbutamol during the four weeks, indicating the progressive development of resistance. The atopic subjects, both asthmatic and non-asthmatic, showed no reduction in the response to salbutamol during the four weeks, nor any change in the response to histamine challenge or in regular peak flow readings. These results demonstrate that asthmatic patients do not develop bronchial beta-adrenoceptor resistance easily and suggests that they and atopic non-asthmatic subjects are less susceptible to its development than normal subjects.     

Salmeterol, a new long acting inhaled beta 2 adrenoceptor agonist: comparison with salbutamol in adult asthmatic patients.

Salmeterol is a new inhaled beta 2 adrenoceptor agonist, which has been shown in animal experiments to produce a more prolonged bronchodilator effect than currently available beta 2 adrenoceptor agonists. It was studied in eight adult asthmatic patients. Each patient received on separate test days salbutamol 200 micrograms and salmeterol 50, 100, and 200 micrograms according to a randomised, double blind, crossover design. FEV1, peak expiratory flow (PEF), heart rate, blood pressure, and tremor were recorded in the clinic for six hours after drug inhalation; PEF was recorded for a further six hours at home. All three doses of salmeterol produced peak increases in FEV1 (mean 0.5-0.8 l) and PEF (71-100 l/min) similar to those produced by salbutamol 200 micrograms (0.5 l and 74 l/min). After salbutamol FEV1 and PEF had returned to baseline within six hours, but after all three doses of salmeterol more than half of the maximum bronchodilator effect remained after 12 hours. The effects of salbutamol and the two lower doses of salmeterol (50 and 100 micrograms) on cardiovascular measurements and on tremor were similar, whereas after salmeterol 200 micrograms there was a small decrease in diastolic blood pressure and an increase in heart rate and tremor. Thus inhaled salmeterol has a long acting bronchodilator action in asthmatic patients. This effect may be of value in the treatment of asthma, particularly in patients with nocturnal symptoms.     

Distribution of galanin immunoreactivity in the respiratory tract of pig, guinea pig, rat, and dog.

Galanin, a newly discovered peptide isolated from porcine intestine, is known to cause contraction in rat smooth muscle preparations and to induce hyperglycaemia in dogs. By the use of radioimmunoassay and immunohistochemical techniques the concentration and distribution of galanin immunoreactivity were determined in several areas of the respiratory tract of five dogs, five guinea pigs, five rats, and two pigs. Antibodies were raised in rabbits to whole unconjugated natural porcine galanin. The highest galanin concentrations were found in the bronchus and the trachea of the dog, guinea pig, rat (2 pmol/g in each case), and pig (less than 1 pmol/g). The lowest galanin concentrations were found in the lung parenchyma. Gel chromatographic analysis in the pig showed one molecular form of galanin coeluting with the porcine galanin standard. By means of the indirect immunofluorescence technique on sections of tissues fixed in benzoquinone solution, galanin was found to be confined to nerve fibres in different regions of the respiratory tract. In the nasal mucosa of the pig nerve fibres containing galanin were distributed around seromucous glands and blood vessels and beneath the epithelium. In the trachea, bronchus, and major intrapulmonary airways of the pig, dog, and guinea pig galanin immunoreactive fibres were detected predominantly in smooth muscle, as well as around seromucous glands and in the adventitia of blood vessels. Rarely, galanin immunoreactive nerve fibres were found in the lung parenchyma. A few galanin immunoreactive ganglion cells also containing vasoactive intestinal polypeptide were found in the adventitia of the tracheobronchial wall of the pig and dog. The distribution of galanin suggests that it may have some influence on airway, vascular, and secretory functions in the mammalian respiratory tract.     

Landiolol, esmolol and propranolol protect from ischemia/reperfusion injury in isolated guinea pig hearts

PURPOSE: Beta blockers are thought to exert beneficial effects on the ischemic heart. The authors examined the effects of landiolol (ONO 1101), a highly selective beta1 antagonist, propranolol, a nonspecific beta blocker, and esmolol, a selective beta1 antagonist, on postischemic contractile recovery. Drugs were given prophylactically. METHODS: Ischemia-reperfusion in isolated guinea pig hearts was induced by stopping the perfusion for 45 min and reperfusing for 60 min. Hearts (n = 7 in each group) were treated with or without propranolol (1 or 10 microM), esmolol (5 or 50 microM), or landiolol (20, 100 or 500 microM) ten minutes before inducing ischemia. RESULTS: At the end of reperfusion, left ventricular pressure (LVP) recovered to 64 +/- 3% of the baseline value in the control group. With 1 and 10 microM propranolol, LVP recovered to 90 +/- 5% and 100 +/- 6% of the baseline value at 60 min after reperfusion, respectively. Fifty microM but not 5 microM of esmolol resulted in restoration of LVP to 97 +/- 17% of the pre-ischemic value at 60 min after reperfusion. In hearts pretreated with 100 and 500 microM landiolol, LVP was restored to 109 +/- 5% and 104 +/- 5% of the baseline value, respectively. Landiolol 100 microM did not depress LVP in the pre-ischemic period. CONCLUSIONS: The present study shows that landiolol, an ultra-short-acting cardioselective beta1 blocker, has cardioprotective effects on ischemia-reperfusion injury in isolated guinea pig hearts. All three beta blockers were equally protective but the intermediate dosage of landiolol preserved LVP during the pre-ischemic period.     

Effect of phenformin on gluconeogenesis from lactate and intracellular pH in the isolated perfused guinea pig liver.

Gluconeogenesis from lactate and hepatic cell pH (pHi) were measured in the isolated perfused livers of starved guinea pigs in the presence and absence of phenformin (phenethylbiguanide). The observed decrease in lactate consumption and glucose output in the presence of phenformin was associated with a fall in pHi. The fall in glucose output observed was considerably greater than accountable for by the decrease in lactate consumption. A possible mechanism for the pathogenesis of clinical lactic acidosis due to phenformin therapy is suggested.     

Possible involvement of cyclic adenosine monophosphate-independent mechanism in the positive chronotropic effect of norepinephrine in the isolated guinea pig right atrium

BACKGROUND: Although both positive chronotropic and inotropic effects of beta-adrenergic stimulation are thought to be mediated by cyclic adenosine 3'5'-monophosphate, phosphodiesterase III inhibitors such as amrinone and milrinone potentiate the positive inotropic effect of catecholamines with minimum influence on the heart rate in clinical setting. The aim of the current study was to compare the positive chronotropic effect of norepinephrine with that of forskolin to elucidate whether cyclic adenosine monophosphate is relevant to the chronotropic effect of norepinephrine. METHODS: Concentration-response curves for the positive chronotropic effects of norepinephrine and forskolin on the spontaneously beating right atria of guinea pigs were determined in the absence and presence of phosphodiesterase inhibitors or ion channel inhibitors. In some experiments, the left atria driven electrically were used to determine the positive inotropic effect of norepinephrine. RESULTS: Norepinephrine and forskolin increased the beating rate in a concentration-dependent manner. The positive chronotropic effect of forskolin was potentiated by amrinone and 3-isobutyl-1-methylxanthine, whereas the positive chronotropic effect of norepinephrine was not potentiated by the phosphodiesterase inhibitors. In contrast, the positive inotropic effect of norepinephrine was potentiated by amrinone. The hyperpolarization-activated inward current inhibitor cesium chloride and L-type voltage-dependent Ca2+ current inhibitor verapamil suppressed the chronotropic effect of norepinephrine, whereas these inhibitors did not affect the chronotropic effect of forskolin. CONCLUSION: Norepinephrine increases the spontaneously beating rate by a different mechanism from that of forskolin, suggesting that cyclic adenosine monophosphate is causally unrelated to the positive chronotropic effect of norepinephrine in the guinea pig heart.     

Renal brush border sodium-sulfate cotransport in guinea pig: effect of age and diet

  Renal adaptation to changes in inorganic sulfate intake and age was studied by comparing sulfate uptake by proximal tubule brush border membrane vesicles (BBMV) from guinea pigs of different ages on relatively high- or low-sulfate diets. Adult (>60 days) or young guinea pigs (<25 days) were fed either a control diet (0.28% sulfur content), a sulfur-free diet, or a high-sulfate diet. After 5 days on the diet, BBMV were obtained and kinetic analysis of ³⁵sulfate uptake was determined. In adult guinea pigs, the low-sulfate diet produced a significant increase in apparent maximal velocity (V _max). In young guinea pigs, a lower sulfate intake did not appreciably increase V _max, but a high-sulfate intake produced a reduction in V _max. The affinity for sulfate (K _m) was not changed in either age group. The dietary sulfate intake did not alter sodium gradient dependent-D-glucose or ³²phosphate V _max. In conclusion, our data indicate that renal inorganic sulfate BBMV uptake is regulated and responds to conditions of increased need (i.e., during the growth phase in young animals and during periods of decreased sulfate availability in adult animals) by increasing BBMV V _max. Received September 9, 1994; received in revised form March 18, 1997; accepted March 20, 1997     

Effects of halothane on electrophysiologic properties and cyclic adenosine 3',5'-monophosphate content in isolated guinea pig hearts.

We studied the effects of halothane on the electrophysiologic and biochemical properties of both Langendorff perfused hearts and single ventricular myocytes isolated from guinea pigs. Isometric contractions of left ventricles in perfused hearts, elicited by atrial pacing, decreased to 14% of control after exposure to 2% halothane-equilibrated perfusate. Subsequently the slow inward Ca2+ current (ICa) was recorded in isolated myocytes with a whole cell voltage clamp technique. ICa, recorded in response to 100-ms depolarizations from -40 mV to 0 mV, was decreased by 2% halothane to 28.4% of control. Halothane-induced ICa depression did not exhibit use dependency. To define a possible site at which halothane acts, we measured the cyclic adenosine 3',5'-monophosphate (cAMP) content of single ventricular myocytes using a radioimmunoassay. Two percent halothane decreased myocardial cAMP content to 68.9% of control. Further addition of dibutyryl cAMP (10(-3) mol/L) partially reversed the depressed contractility during 2% halothane administration in perfused hearts. In conclusion, the present study demonstrated that the decrease of myocardial cAMP by halothane was due to a direct action, at least partly, and not to other factors such as catecholamines, and suggested that the decreases in contractility and ICa were induced possibly through the decrease in cellular cAMP.     

Sevoflurane and isoflurane do not enhance the pre- and postischemic eicosanoid production in guinea pig hearts

Eicosanoids and volatile anesthetics can influence cardiac reperfusion injury. Accordingly, we analyzed the effects of sevoflurane and isoflurane applied in clinically relevant concentrations on the myocardial production of prostacyclin and thromboxane A2 (TxA2) and on heart function. Isolated guinea pig hearts, perfused with crystalloid buffer, performed pressure-volume work. Between two working phases, hearts were subjected to 15 min of global ischemia followed by reperfusion. The hearts received no anesthetic, 1 minimum alveolar anesthetic concentration (MAC) isoflurane (1.2 vol%), or 0.5 and 1 MAC sevoflurane (1 vol% and 2 vol%), either only preischemically or pre- and postischemically. In additional groups, cyclooxygenase function was examined by an infusion of 1 microM arachidonic acid (AA) in the absence and presence of sevoflurane. The variables measured included the myocardial production of prostacyclin, TxA2 and lactate, consumption of pyruvate, coronary perfusion pressure, and the tissue level of isoprostane 8-iso-PGF2alpha. External heart work, determined pre- and postischemically, served to assess recovery of heart function. Volatile anesthetics had no impact on postischemic recovery of myocardial function (50%-60% recovery), perfusion pressure, lactate production, or isoprostane content. Release of prostacyclin and TxA2 was increased in the early reperfusion phase 5-8- and 2-4-fold, respectively, indicating enhanced AA liberation. Isoflurane and sevoflurane did not augment the eicosanoid release. Only 2 vol% sevoflurane applied during reperfusion prevented the increased eicosanoid formation in this phase. Infusion of AA increased prostacyclin production approximately 200-fold under all conditions, decreased pyruvate consumption irreversibly, and markedly attenuated postischemic heart work (25% recovery). None of these effects were mitigated by 2 vol% sevoflurane. In conclusion, only sevoflurane at 2 vol% attenuated the increased liberation of AA during reperfusion. Decreased eicosanoid formation had no effect on myocardial recovery in our experimental setting while excess AA was deleterious. Because eicosanoids influence intravascular platelet and leukocyte adhesion and activation, sevoflurane may have effects in reperfused tissues beyond those of isoflurane. IMPLICATIONS: In an isolated guinea pig heart model, myocardial eicosanoid release was not increased by isoflurane or sevoflurane, either before or after ischemia. Sevoflurane (2 vol%) but not isoflurane attenuated the increased release of eicosanoids during reperfusion.     

Experimental study of pegylated liposomal hemoglobin on norepinephrine release and reperfusion arrhythmias in isolated guinea pig hearts.

PURPOSE: Under myocardial reperfusion conditions, hemoglobin (Hb)-based artificial blood showed effectiveness for post-ischemic dysfunction. However, there are no studies about the effects of this product on reperfusion arrhythmias (ventricular fibrillation, VF) associated with norepinephrine (NE) release. This study was to evaluate the effects of the timing of the administration of pegylated liposomal Hb (LHb, P(50)=40-45 mmHg, 1 mg/mL) on NE release and VF. MATERIALS AND METHODS: Isolated guinea pig hearts (n=6 in each group) were randomly divided into four groups in Krebs-Henseleit solution being supplemented or not with LHb as follows: pre-ischemia (PRE), reperfusion (REP), or PRE+REP groups. The hearts were perfused for 30 min (preischemic period) and then subjected to 30 min of global ischemia, followed by 30 min of reperfusion with a normothermic Langendorff apparatus at 30 mm Hg aortic pressure in a constant pressure model. RESULTS: No differences were documented among the four groups in heart rate, left ventricular-developed pressure, or coronary flow rate. However, the REP group significantly decreased the duration of VF and NE release, but it did not inhibit the incidence of VF. CONCLUSION: These results suggest that the administration of LHb, especially with the timing of reperfusion, might prevent reperfusion arrhythmias linked to the inhibition of NE release.     

Ultrastructural features and possible functional role of kit-positive interstitial cells in the guinea pig corpus cavernosum

The objective of the present study was to identify kit-positive interstitial cells (ICs) in guinea pig corpus cavernosum and examine their relationships with adjacent smooth muscle cells (SMCs) and intramural nerves. In addition, we investigated the possible involvement of ICs in nitric oxide (NO)-mediated relaxation of corpus cavernosum smooth muscle (CCSM). ICs were identified by their immunoreactivity to the kit receptor, a cell surface marker encoded by c-kit proto-oncogene and specific for interstitial cells of Cajal. ICs were abundantly distributed in guinea pig corporal tissues. Ultrastructural investigation by conventional transmission electron microscopy revealed the ultrastructural features of ICs and gap junctions located between ICs and adjacent SMCs, furthermore, a close contact between ICs and intramural nerves for the first time. Western blot analysis of purified ICs by fluorescence-activated cell sorting revealed coexpression of soluble guanylate cyclase (sGC)α1, sGCβ1 and kit receptor tyrosine kinase protein in them. These observations imply that ICs express the NO-sensitive sGC molecule and may be involved in the NO-mediated relaxation of CCSM in the guinea pig corpus cavernosum.