Interaction of the beta adrenergic receptor antagonist bucindolol with serotonergic receptors.

Bucindolol is a nonselective beta-adrenergic receptor antagonist that has additional vasodilating properties. Because some beta-adrenergic receptor antagonists such as cyanopindolol are used as 5-HT1A/5-HT1B receptor antagonists, we tested the hypothesis that bucindolol can interact with 5-HT receptors. Both in vitro and in vivo methods were used to examine the interaction of bucindolol with 5-HT receptors relevant to the cardiovascular system-the 5-HT1A, 5-HT1D, 5-HT2A, and 5-HT2B receptors-and with alpha1-adrenergic receptors. In binding studies, bucindolol displayed high affinity for the 5-HT1A receptor (Ki, 11 nM), modest affinity for the 5-HT2A receptor (Ki, 382 nM), and no measurable affinity for the 5-HT1D receptor; binding affinity for the 5-HT2B receptor was not studied. Bucindolol also displayed significant binding affinity (Ki, 69 nM) for the alpha1-adrenergic receptors. Alpha1-Adrenergic receptor antagonist activity was confirmed by the ability of bucindolol (1 mg/kg) to act as a competitive antagonist against 0.01-30 microg/kg phenylephrine-induced pressor responses in conscious rats. In conscious permanently instrumented rats, bucindolol (0.1-3.0 mg/kg, i.v.) did not cause bradycardia similar to that elicited by the 5-HT1A-receptor agonist 8-OH-DPAT (3-300 microg/kg, i.v.), nor did bucindolol (1 mg/kg) block the 8-OH-DPAT-induced bradycardia. Bucindolol (10(-9)-10(-5) M) did not cause relaxation in the PGF2alpha-contracted, endothelium-intact porcine coronary artery, nor did bucindolol (10(-5) M) block 5-HT-induced coronary artery relaxation, indicating that bucindolol does not have significant interactions at the 5-HT1D receptor. Bucindolol also displayed no agonist activity at the 5-HT2A and 5-HT2B receptor (endothelium-denuded rat thoracic aorta and rat stomach fundus, respectively), but did act as a weak 5-HT2A-receptor antagonist (-log K(B) [M] = 5.4+/-0.1) and 5-HT2B-receptor antagonist (-log K(B) [M] = 7.8+/-0.1). Thus, these data suggest that bucindolol lacks the ability to activate the 5-HT1A, 5-HT1D, 5-HT2A, and 5-HT2B receptor, but can block alpha1-adrenergic receptors and act as a weak 5-HT2A- and 5-HT2B-receptor antagonist. The relevance of these serotoninergic effects as it pertains to the mechanism of bucindolol-induced vasodilation is unknown.

Effects of candesartan cilexetil in patients with severe systemic hypertension. Candesartan Cilexetil Study Investigators.

The efficacy, tolerability, and safety of the potent angiotensin II receptor blocker candesartan cilexetil were evaluated in 217 adult patients (68% men, 41% black) with severe systemic hypertension on background therapy with hydrochlorothiazide (HCTZ) in a 4-week, multicenter, randomized, double-blind, placebo-controlled study. Patients with sitting diastolic blood pressure (BP) > or =110 mm Hg during the placebo run-in received HCTZ 12.5 mg once daily for 1 week. Those with sitting diastolic BP >95 mm Hg after the HCTZ run-in were randomized (2:1) to receive candesartan cilexetil 8 mg once daily (n = 141) or placebo (n = 76), plus HCTZ 12.5 mg. After 1 week of double-blind treatment, patients with sitting diastolic BP > or =90 mm Hg were uptitrated to candesartan cilexetil 16 mg once daily or matching placebo, plus HCTZ 12.5 mg; 84% required uptitration. Primary efficacy measurement was a change in trough (24+/-3 hours after treatment) sitting diastolic BP from the end of the HCTZ run-in to double-blind week 4. Mean changes in systolic and diastolic BP were significantly greater with candesartan cilexetil than with placebo, -11.3/-9.1 mm Hg versus -4.1/-3.1 mm Hg, p <0.001/p <0.001, respectively. Patients with higher sitting diastolic BP at the end of the HCTZ run-in tended to have greater decreases in BP (p <0.05). Most patients (53%) receiving candesartan cilexetil were responders (diastolic BP <90 mm Hg or > or =10 mm Hg decrease) and 32% were controlled (diastolic BP <90 mm Hg). Tolerability and safety profiles were similar in the candesartan and placebo groups. In conclusion, candesartan cilexetil 8 to 16 mg once daily was an effective and well-tolerated therapy for lowering BP when added to HCTZ 12.5 mg in a diverse population of patients with severe systemic hypertension in the United States.

Candesartan cilexetil: comparison of once-daily versus twice-daily administration for systemic hypertension. Candesartan Cilexetil Study Investigators.

This randomized, double-masked, placebo-controlled, forced-titration, parallel-arm study was designed to compare the blood pressure (BP)-lowering effect of candesartan cilexetil, a potent antagonist of the angiotensin II receptor subtype AT1, administered once daily with that of the same agent administered twice daily at the same total daily dose of 16 mg. After a 4- to 5-week placebo run-in period, 277 patients with a sitting diastolic BP of 95 to 109 mm Hg were randomly allocated to receive placebo (n = 92) or candesartan cilexetil 8 mg once daily for 4 weeks, followed by forced titration to either 16 mg once daily (n = 91) or 8 mg twice daily (n = 94) for 4 weeks. At 8 weeks, mean reductions in trough sitting diastolic BP were similar for the once- and twice-daily treatment groups (9.4 and 10.3 mm Hg, respectively). After 8 weeks of treatment, no statistically significant differences were observed in diastolic or systolic BP, peak or trough BP, or sitting or standing BP between the 2 active-treatment groups. The rates of positive responses (defined as a trough sitting diastolic BP of <90 mm Hg or a decrease in BP of > or =10 mm Hg) were also similar (approximately 60%) in the once- and twice-daily candesartan cilexetil groups. Furthermore, placebo-corrected trough-to-peak ratios for sitting diastolic BP exceeded 75% for both candesartan cilexetil regimens, indicating a persistent 24-hour duration of drug effect. Ambulatory BP monitoring performed in a subset of patients (n = 44) confirmed the consistent 24-hour BP-lowering effect and preservation of diurnal variation with once-daily dosing. No significant between-group differences were observed in the incidence or severity of clinical or laboratory adverse events. The results of this study suggest that identical daily doses of candesartan cilexetil administered once or twice daily have comparable efficacy and tolerability and that no additional clinical benefit is derived from twice-daily administration.

Effective dose range of candesartan cilexetil for systemic hypertension. Candesartan Cilexetil Study Investigators.

The results of this randomized, double-blind, placebo-controlled, forced-dose titration study in a diverse population of hypertensive patients in the US indicate that candesartan cilexetil has clinically meaningful dose-related blood pressure-lowering effects and that maximum blood pressure reduction is achieved with doses of 16 and 32 mg given once daily. This study confirms that candesartan cilexetil is a highly effective antihypertensive agent with an excellent tolerability and safety profile, without dose-related adverse effects.

Comparative effects of candesartan cilexetil and losartan in patients with systemic hypertension. Candesartan Versus Losartan Efficacy Comparison (CANDLE) Study Group.

The antihypertensive efficacy and tolerability of the novel angiotensin-II (A-II) receptor blocker candesartan cilexetil and the prototype A-II receptor blocker, losartan, were compared in an 8-week, multicenter, double-blind, randomized, parallel-group, titration-to-effect study of 332 adults (42% women, 12% black) with systemic hypertension (sitting diastolic blood pressure [DBP] 95-114 mmHg, inclusive). In patients with a mean trough (24 +/- 3 hours after dose) sitting DBP of 90 mmHg or higher after 4 weeks of once daily administration of candesartan 16 mg or losartan 50 mg, dose was titrated up to candesartan 32 mg or losartan 100 mg once daily. The candesartan regimen was significantly more effective than the losartan regimen in reducing trough sitting DBP at week 8 (11.0 mmHg versus 8.9 mmHg). Candesartan also produced numerically greater reductions in secondary blood pressure parameters, including sitting systolic blood pressure (SBP), trough standing DBP and SBP, and peak (6 +/- 2.5 hours after dose) sitting and standing DBP and SBP. Responder rates (sitting DBP < 90 mmHg or reduction in blood pressure of > or = 10 mmHg) and control rates (sitting DBP <90 mmHg) were higher with candesartan (64% versus 54% and 54% versus 43%, respectively). A total of 1.9% of the patients taking candesartan and 6.5% of those taking losartan discontinued prematurely because of adverse events or lack of efficacy.

Effects of candesartan cilexetil in patients with systemic hypertension. Candesartan Cilexetil Study Investigators.

The objectives of this double-blind, multicenter, randomized, parallel-arm, placebo-controlled study were to evaluate the dose-related efficacy, tolerability, and safety of candesartan cilexetil, a potent, AT1 selective, long-acting angiotensin II receptor blocker, in 365 adult patients with systemic hypertension and mean sitting diastolic blood pressure (BP) of 95 to 114 mm Hg. Patients received either placebo or candesartan cilexetil 2, 4, 8, 16, or 32 mg once daily for 8 weeks. All doses of candesartan cilexetil reduced trough (24 hours after treatment) sitting diastolic and systolic BP significantly compared with placebo (p < 0.005). A significant (p < or = 0.0001) dose response was evident, with greater decreases in BP at higher doses. Mean changes in BP were -10.7/-7.8 mm Hg and -12.6/-10.2 mm Hg in the 16- and 32-mg groups, respectively, versus -0.3/-2.6 mm Hg in the placebo group. The 16- and 32-mg doses were consistently significantly superior to placebo in antihypertensive effect with regard to all BP measurements, including peak (6 hours after treatment), trough, sitting, and standing measurements of diastolic and systolic BP. Responder rates (trough sitting diastolic BP < 90 or > or = 10 mm Hg BP decrease) were 54% and 64% for the 16- and 32-mg groups, respectively. Tolerability and safety profiles were similar to placebo at all doses. In conclusion, candesartan cilexetil administered once daily effectively reduces BP in a dose-related manner while maintaining safety and tolerability; doses of 16 and 32 mg are most effective for treatment of hypertension.

LY215840, a high-affinity 5-HT7 receptor ligand, blocks serotonin-induced relaxation in canine coronary artery.

The canine coronary artery possesses a smooth muscle relaxant serotonin (5-HT) receptor distinct from previously characterized 5-HT receptors. On the basis of the ability of LY53857 to block weakly coronary smooth muscle relaxation to 5-HT, we examined several structurally related ergolines in endothelium denuded rings of canine coronary artery precontracted with PGF2 alpha (10 microM). 5-HT (10 nM-100 microM)-induced relaxation was antagonized competitively by the ergoline esters LY53857 (-log KB = 6.5) and sergolexole (-log KB = 6.4) and by the ergoline amide amersergide, (-log KB = 6.7). In contrast to the relatively low affinity of these ergolines, LY215840, another ergoline amide, antagonized 5-HT-induced relaxation in a competitive manner with the highest affinity (-log KB = 8.3). This effect was independent of the 5-HT2 receptor affinity of these ergolines, because LY215840, LY53857, sergolexole and amesergide all possessed similar 5-HT2 receptor affinity. Further, all four ergolines possessed affinity for the human 5-HT7 receptor, and LY215840 had the highest 5-HT7 receptor affinity (Ki = 14.7 nM). Finally, in vascular smooth muscle under basal tone, LY215840 (1 microM) blocked the relaxant response to high concentrations of 5-HT and 5-MeOT without altering their contractile potency. LY215840 (1 microM) did not alter contraction to sumatriptan, an agent that lacks relaxant activity. In contrast, LY215840 (1 microM) markedly potentiated contraction to 5-carboxamidotryptamine, the most potent coronary relaxant agonist and the agonist with the highest 5-HT7 receptor affinity. The ability of LY215840 to block the relaxant 5-HT receptor in canine coronary artery may reflect its 5-HT7 receptor antagonist activity and make it a useful tool to probe the relationship between the 5-HT7 receptor and the coronary vasoactive properties of 5-HT.

Temperature-stable bandpass filters deposited with plasma ion-assisted deposition.

Plasma ion-assisted deposition with an advanced plasma source was investigated to produce narrow-bandpass filters in the near-infrared spectral range for telecommunication applications. The multilayer coatings were qualified by the optical performance, the vacuum-to-air behavior, the temperature stability, and the film stress. TiO(2)/SiO(2) and Ta(2) O(5)/SiO (2) material combinations were used and compared. The coating system produced low absorbing multilayers with a very low coefficient of expansion and low stress. The coefficient of expansion was in the low 10(-6) °C range, and film stress values in the range between 1 and 2 × 10(8) N/m(2) were obtained. TiO(2)/SiO(2) was the preferred material combination. The optical monitoring system allowed the production of bandpass filters with a performance close to that of the theoretical values.

Thoracoscopic staging of esophageal cancer: a prospective, multiinstitutional trial. Cancer and Leukemia Group B Thoracic Surgeons.

BACKGROUND: Lymph node metastasis has been shown to be an important prognosticator in esophageal cancer. A prospective, multiinstitutional study of thoracoscopic lymph node staging in patients with biopsy-proven esophageal cancer was undertaken at University of Maryland, Medical University of South Carolina, and Brigham and Women's Hospital. METHODS: Forty-nine patients underwent thoracoscopic staging between September 1991 and August 1993. Five procedures were incomplete due to adhesions. Preoperative computed tomography, magnetic resonance imaging, esophageal ultrasound, and bronchoscopy were performed. After our initial experience with the left side of the chest, thoracoscopic staging was done through the right side of the chest unless specific indications dictated otherwise. Beginning in January 1993 routine laparoscopic/mini-laparotomy lympho node staging of the celiac axis was performed. RESULTS: Satisfactory thoracoscopic lymph node staging was achieved in 44 patients (95%). Of 33 patients undergoing esophageal resection, 29 were correctly staged (88%). Since initiating concomitant laparoscopic lymph node staging, we have correctly staged all of the last 9 patients with regard to celiac lymph nodes as well. Information regarding T status obtained at thoracoscopy was as follows: 3 patients were correctly "downstaged" to T3 despite preoperative noninvasive tests suggesting T4. In 2 patients thoracoscopy correctly predicted T4 invasion, whereas in 2 patients, thoracoscopy missed T4 lesions. CONCLUSIONS: Thoracoscopy is a valuable tool for staging intrathoracic tumors. Preoperative staging of esophageal cancer may allow better allocation of adjuvant therapy. This pilot study suggests that thoracoscopic staging can correctly predict thoracic lymph node status with high accuracy and aid in better defining T status.

Is the "atypical" beta-receptor in the rat stomach fundus the rat beta 3 receptor?

The rat gastric fundus is known to possess an "atypical" beta-adrenergic receptor that mediates relaxation to isoproterenol. The purpose of this study was to characterize the relationship between this "atypical" beta receptor in the rat stomach and the cloned rat beta 3 receptor by taking advantage of highly selective pharmacological and molecular biological probes of the beta 3 receptor. Nuclease protection analysis of RNA from the rat gastric fundus identified beta 3 receptor mRNA whose levels in the stomach were exceeded only by those in adipose tissue. Pharmacological analysis of the recombinant rat beta 3 receptor expressed in Chinese hamster ovary cells indicated low affinity of propranolol with a Ki value of 2.3 microM. Therefore, 0.3 microM propranolol was chosen as a concentration that would completely block beta 1 and beta 2 receptors (Ki = 1-5 nM) but would leave beta 3 receptors largely intact in the rat stomach fundus. In the presence of propranolol, several beta-adrenergic receptor agonists relaxed the rat stomach fundus with a rank potency order of (R,R)-5-[2-[[2-(3-chlorophenyl)-2-hydroxyethyl]-amino]-propyl]1,3- benzodioxole-2,2-dicarboxylate (CL316,243) > isoproterenol > norepinephrine = epinephrine = dl-4-3[(1,1-dimethylethyl)amino]-2- hydroxylproproy]1,3 dihydro-2H-benzimidazol-2-one hydrochloride (CGP12177) > clenbuterol > terbutaline > pindolol. Isoproterenol, norepinephrine and epinephrine were full agonists, whereas (R,R)-5-[2-[[2-(3-chlorophenyl)-2- hydroxyethyl]-amino]-propyl]1,3-benzodioxole-2,2-dicarboxylate was only a partial agonist with 66% intrinsic activity relative to isoproterenol.(ABSTRACT TRUNCATED AT 250 WORDS)

Vasoconstrictor action of angiotensin I-convertase and the synthetic substrate (Pro11,D-Ala12)-angiotensin I.

A chymase (also referred to as angiotensin I-convertase) specific for the conversion of angiotensin (Ang) I to Ang II has been identified in human heart. This serine protease is also present in dog and marmoset vasculature. We examined the vasoconstrictor effects of Ang II putatively generated from an angiotensin-converting enzyme (ACE)-resistant convertase synthetic substrate (SUB) in vivo and in vitro. In marmosets, SUB (7 to 700 micrograms/kg i.v.) or Ang I (0.1 to 30 micrograms/kg) caused similar dose-dependent increases in mean arterial pressure (10 to 100 mm Hg) and decreases in heart rate. Pressor effects of SUB were slightly attenuated at low (but not high) doses by captopril (CAP, 1 mg/kg i.v.) and blocked by losartan (5 mg/kg i.v.); in contrast Ang I pressor effects were substantially blocked by both. In isolated canine superior mesenteric artery, Ang I-induced contraction was eliminated by losartan and reduced but not eliminated by 10 mumol/L CAP. When combined with the serine protease inhibitor chymostatin, CAP eliminated Ang I-induced contraction, but chymostatin alone had no effect. SUB-induced contraction was not blocked by CAP but was equally blocked by chymostatin (25 mumol/L) alone or by the combination of CAP (10 mumol/L) and chymostatin (25 mumol/L); losartan (10 mumol/L) eliminated SUB-induced responses. Previous studies have suggested that Ang I-convertase is important for production of Ang II in the heart. Our results are consistent with a potential role for Ang I-convertase in the production of Ang II in the vasculature, resulting in Ang II-mediated vasoconstriction.

Serotonin-induced contraction in canine coronary artery and saphenous vein: role of a 5-HT1D-like receptor.

The identity of the serotonin (5-HT) receptor(s) that mediate(s) contraction in canine coronary artery and saphenous vein remains controversial. Ring segments of endothelium-denuded coronary artery and helical strips of saphenous vein were suspended in organ chambers for measurement of isometric force. 5-HT, alpha Me-5-HT and sumatriptan contracted both coronary artery and saphenous vein and the non-selective 5-HT receptor antagonist 1-naphthylpiperazine (100nM) blocked 5-HT- and sumatriptan-induced contraction in both tissues. The agonist rank order potency for contraction (5-HT > sumatriptan > alpha Me5-HT > 5-MeOT > 5-MeT) was similar in both tissues and was consistent with that for a 5-HT1D receptor. Oligonucleotide primers specific for the 5-HT1D receptor sequence were designed for use in a polymerase chain reaction (PCR). cDNA derived from total RNA or mRNA from canine tissues was used in the PCR. PCR resulted in the amplification of a 632 base pair sequence in both canine coronary artery and saphenous vein; consistent with that expected for the 5-HT1D receptor. Southern blot analysis, with an oligonucleotide probe internal to the sequence amplified by the PCR primers, confirmed that the sequence amplified by PCR was the 5-HT1D receptor. Thus, the 5-HT1D receptor is expressed in canine coronary artery and saphenous vein and taken together with the pharmacological data, supports the possibility that a 5-HT1D-like receptor mediates contraction in these two tissues.

Serotonin-induced contraction in porcine coronary artery: use of ergolines to support vascular 5-hydroxytryptamine2-receptor heterogeneity.

Serotonin-induced contraction in porcine coronary artery was studied in ring segments of coronary artery without endothelium. 5-hydroxytryptamine (5-HT), 5-methoxytryptamine (5-MeOT) and alpha-methyl-5-HT (alpha Me-5-HT) concentration-dependently contracted vessels with similar maximal force. The agonist rank order potency was 5-HT > alpha Me-5-HT > 5-MeOT. Neither prazosin (1 microM) nor tetrodotoxin (0.3 microM) significantly altered 5-HT-induced contraction, ruling out activation of alpha-1 adrenoceptors and sodium channels in the contractile response, respectively. Using 5-MeOT as the prototype agonist, cyanopindolol blocked contraction with an antagonist dissociation constant lower than expected for 5-HT1-receptor blockade and ICS 205-930 (10 microM) did not affect 5-MeOT-induced contraction. Five structurally distinct 5-HT2-receptor antagonists (ketanserin, cisapride, spiperone, MDL11939, ICI169369) blocked 5-HT-induced contraction with antagonist dissociation constants similar to reported 5-HT2-receptor affinities. Two ergoline-based 5-HT2-receptor antagonists, LY53857 and sergolexole, blocked 5-HT-induced contraction with antagonist dissociation constants lower than expected for vascular 5-HT2-receptor blockade. Based on the agonist profile and the fact that ICS 205-930 and cyanopindolol were not potent antagonists, the 5-HT receptor-mediating contraction does not represent either the 5-HT1A/B/C/D, 5-HT3 or 5-HT4 receptor. Rather, based on the affinity of several established 5-HT2-receptor antagonists, a 5-HT2 receptor mediates contraction in porcine coronary artery. However, the low antagonist affinity of the ergolines (i.e., LY53857 and sergolexole) suggests that heterogeneity of 5-HT2 receptors may exist among species.

Serotonin-induced relaxation in canine coronary artery smooth muscle.

Serotonin (5-HT) is a potent contractile agonist in canine coronary artery devoid of endothelium; however, in higher concentrations 5-HT produces concentration-dependent relaxation by activating an as yet uncharacterized receptor. This study explored the possibility that 5-HT-induced relaxation was mediated by interaction with a member of the 5-HT1, 5-HT2, 5-HT3, or 5-HT4 receptor family. 5-HT, 5-carboxamidotryptamine and 5-methoxytryptamine produced concentration-dependent relaxation in vitro in tissues precontracted with prostaglandin F2 alpha (10 microM). The agonist rank order potency for relaxation was 5-carboxamidotryptamine > 5-HT > 5-MeOT. 8-hydroxydipropylaminotetralin (8-OH-DPAT), dipropyl-5-CT, 5-methyltryptamine, sumatriptan, alpha-methyl-5-HT and 2-methyl-5-HT did not produce significant relaxation. The 5-HT1/beta adrenergic receptor antagonist propranolol (1 microM) did not antagonize 5-HT-induced relaxation. 5-HT-induced relaxation was not blocked by tetrodotoxin (0.3 microM), suggesting that neuronal depolarization to release mediators from nerves was not responsible for the relaxation. Neither ketanserin (1 microM) nor ritanserin (1 microM) antagonized 5-HT-induced relaxation, suggesting that 5-HT2 and 5-HT1C receptors do not mediate relaxation. ICS 205-930 (10 microM), a 5-HT3/5-HT4 receptor antagonist, shifted the 5-HT concentration-response curve modestly to the right (pKB = 5.1 +/- 0.1). Cisapride, a 5-HT4 receptor agonist, was not effective either as an agonist (up to 10 microM), or as an antagonist (1 microM) of 5-HT-induced relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the serotonin receptors that mediate smooth muscle contraction in canine and porcine coronary artery.

Serotonin (5-HT) is one important mediator of the coronary vasospasm and occlusion associated with thrombosis and atherosclerosis. 5-HT concentration-dependently contracted both canine and porcine coronary artery rings in vitro. In the dog, 5-HT-induced contraction was not blocked by either LY53857 (1 microM) or ketanserin (1 microM), but was blocked by the nonselective 5-HT receptor antagonist 1-naphthylpiperazine (1-NP) (100 nM), indicating 5-HT receptor involvement. Unlike the dog, both LY53857 (1 microM) and ketanserin (30 nM) antagonized 5-HT-induced contraction in pig arteries. Dissociation constants for LY53857 and ketanserin in porcine arteries were compared with those in rat jugular vein, a tissue possessing a well characterized 5-HT2 receptor. Both LY53857 (3 nM) and ketanserin (3 nM) antagonized 5-HT-induced contraction in rat jugular vein; however, the affinities of LY53857 and ketanserin in the rat jugular vein were significantly higher than those in the pig coronary. The rank order contractile potency for 5-HT, (alpha Me-5-HT) and sumatriptan in porcine coronary artery was consistent with that established for a 5-HT2 receptor, whereas the rank order potency in canine coronary artery indicated non-5-HT2 receptor involvement. Sumatriptan, a 5-HT1D receptor-selective agonist, was equieffective to 5-HT in contracting the canine coronary artery, a response inhibited by 1-NP (100 nM). Sumatriptan failed to contract either the pig coronary or rat jugular vein. In summary, significant differences exist in the 5-HT receptors that mediate contraction between the canine and porcine coronary artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Protein kinase C and phospholipase C in adenosine receptor-mediated relaxation in coronary artery.

The effect of adenosine, 2-chloroadenosine (CAD), and 5'-(N-ethylcarboxamido)-adenosine (NECA) on the contraction produced by phorbol 12,13-dibutyrate (PDB) was investigated in porcine coronary artery in vitro to determine whether adenosine receptor-mediated relaxation was linked to protein kinase C. Also, the coronary relaxation produced by adenosine and NECA in KCl-contracted coronary rings was investigated before and after treatment with the phospholipase C inhibitor neomycin to examine a possible link between phospholipase C and adenosine receptor-mediated relaxation. Ring segments of coronary artery were suspended in organ baths for measurement of isometric force. PDB (10 nM-1 microM) caused concentration-dependent contraction, and this response was significantly attenuated by pretreatment with the protein kinase C inhibitor staurosporine (200 nM) but not 1-(5-isoquinolinylsulfonyl)-2-methyl-piperazine (10 microM). Treatment of rings with either adenosine, CAD, or NECA (100 microM) significantly attenuated the PDB-induced contraction, whereas treatment with either sodium nitroprusside (SNP; 1 microM) or isoproterenol (Isop; 1 microM) did not affect the contraction produced by PDB. The attenuation of the PDB-induced contraction by adenosine and its analogues was blocked by prior treatment of the coronary rings with 8-phenyltheophylline (10 microM). In a separate series of experiments, pretreatment of rings with the phospholipase C inhibitor neomycin (1 mM) resulted in a significant attenuation of the relaxing response to both adenosine and NECA while having no significant effect on the relaxation-response to SNP or Isop. These results provide indirect evidence that adenosine receptor-mediated relaxation in porcine coronary artery may be linked to modulation of protein kinase C and phospholipase C.

Inhibition of adenylate cyclase attenuates adenosine receptor-mediated relaxation in coronary artery.

This study was designed to evaluate whether the adenylate cyclase inhibitor 2',5'-dideoxyadenosine (DDA) would attenuate the relaxation produced by adenosine analogs in order to provide functional evidence in support of the working hypothesis that adenosine receptor-mediated relaxation of coronary artery involves adenylate cyclase. Rings from porcine left anterior descending coronary artery were mounted in organ chambers for measurement of isometric force. Rings contracted with KCl (30 mM) relaxed in a concentration-dependent manner to 2-chloroadenosine (CAD), 5'-N-ethylcarboxamidoadenosine (NECA), isoproterenol, sodium nitroprusside (SNP) and forskolin. Treatment of coronary rings with DDA (50 microM) significantly attenuated the relaxation produced by CAD, NECA, forskolin and isoproterenol, but had no effect on the relaxation response to SNP. The nucleoside transport inhibitor dilazep (10 microM) completely reversed the inhibitory effect of DDA on the relaxation produced by forskolin and CAD, whereas dilazep only partially reversed the DDA inhibition of NECA-induced relaxation. In a membrane preparation from porcine coronary artery CAD, but not NECA, increased cyclic AMP production in a GTP-dependent manner. DDA significantly decreased basal cyclic AMP production and also decreased CAD-, forskolin-, GTP- and NaF-stimulated cyclic AMP production. These results provide functional and biochemical evidence in support of the working hypothesis that adenosine receptor-mediated coronary relaxation involves adenylate cyclase. Furthermore, the results from this study suggest that the signaling mechanisms responsible for adenosine receptor-mediated coronary relaxation are more complicated than a single receptor coupled with adenylate cyclase because 1) dilazep completely reversed the inhibitory effect of DDA on the CAD relaxation but not the NECA relaxation, and 2) NECA did not increase cyclic AMP production.

G proteins subserve relaxations mediated by adenosine receptors in human coronary artery.

The coupling of the human coronary adenosine receptor to a G protein was investigated in vitro. Hearts were obtained from accidental death victims and the left anterior descending coronary artery (LAD) was taken for experimentation. Cholera toxin (CT) and pertussis toxin (PT) ADP-ribosylated proteins with Mr of 45, 49 (CT), and 41 (PT) kDa. Both processes were sensitive to GTP gamma S. In LAD rings contracted with KCl, adenosine (ADO) and its analogs 5'-N-ethylcarboxamidoadenosine (NECA) and 2-chloroadenosine (CAD) produced concentration-dependent relaxation. These concentration-response curves were shifted to the right significantly in the presence of the competitive ADO receptor antagonist, 8-phenyltheophylline (8-PT), indicating the involvement of ADO receptors. Treatment with NaF/AlCl3, which uncouples G protein-mediated responses, caused significant attenuation of the relaxation responses to ADO, NECA, and CAD. When the rings were incubated with CT, there was an attenuation of the relaxations produced by ADO, CAD, NECA, and isoproterenol (ISOP). Incubation with PT resulted in significant inhibition of the relaxations induced by ADO, NECA, and CAD. The results provide evidence for the presence of CT- and PT-sensitive G protein(s) subserving the relaxing adenosine receptors in human coronary artery.

Risk factors for postoperative infection.

During a 4-year period, we collected prospective epidemiologic data and intraoperative wound cultures from 1,852 surgery patients at a university-affiliated community hospital in order to identify the critical risk factors for postoperative wound infections and study the impact of perioperative antibiotics on the bacteriology of infected wounds. Stepwise logistic regression analysis revealed four risk factors that were independent of each other and highly predictive for subsequent wound infection. These were the surgical wound class, American Society of Anesthesiologists physical status grouping, duration of surgery, and results of intraoperative cultures. Addition of other variables to our model did not increase the predicted probability of infection. Even though patients with positive intraoperative cultures had an increased rate of infection, this information had limited clinical utility. The predictive value of a positive culture was low (32%), false-positive rate was high (82%), and concordance with isolates from infected wounds was low (41% when both cultures were positive). Patients who had received perioperative antibiotics and who developed infections were frequently infected with organisms that were resistant to the perioperative drug regimen, compared with patients who had not received antibiotics. A better understanding of the variables that affect the epidemiology and pathogenesis of postoperative wound infection will enable us to make more valid comparisons of rates among hospitals, help us to develop more effective infection control strategies and provide us with more effective treatments.

Adenosine receptor-mediated coronary artery relaxation and cyclic nucleotide production.

We investigated the involvement of adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) in adenosine (ADO) receptor-mediated coronary artery relaxation. Rings from left anterior descending coronary artery, with the endothelium mechanically removed, contracted with prostaglandin F2 alpha and relaxed in a concentration-dependent manner to ADO, 2-chloroadenosine (CAD), l-N6-(2-phenylisopropyl)adenosine (R-PIA), and 5'-(N-ethylcarboxamido)adenosine (NECA). These relaxations were blocked by addition of the ADO receptor antagonist 8-(sulfophenyl)theophylline (8-SPT), indicating ADO receptor involvement. In an endothelium-free membrane preparation, ADO, CAD, and R-PIA all stimulated adenylate cyclase activity in a concentration-dependent manner, and these responses were blocked by 8-SPT. The increase in adenylate cyclase activity produced by ADO, CAD, and R-PIA was completely dependent on the presence of guanosine 5'-triphosphate, suggesting G protein involvement. Surprisingly, NECA and CGS-21680 did not increase adenylate cyclase activity. Unlike atrial natriuretic factor, neither NECA, CAD, R-PIA, nor ADO increased guanylate cyclase activity, suggesting that cGMP is not involved in ADO receptor-mediated relaxation. Data presented in this study support the hypothesis that ADO receptor-mediated coronary artery relaxation may involve cAMP; however, the inability of NECA and CGS-21680 to stimulate adenylate cyclase suggests that the ADO receptor-signaling mechanisms in coronary artery may be more complicated than agonist interaction with a single adenylate cyclase-coupled A2 adenosine receptor.