Roles of P2-purinoceptors in the cardiovascular system

Effect of diadenosine tetraphosphate (AP4A) on coronary arterial microvessels in the beating canine heart

Diadenosine tetraphosphate (AP4A) can be released from activated platelets and the present study examined its effect on coronary arterial microvessels. The role of purinoceptors in the coronary microcirculation in vivo was also investigated. In open chest dogs, coronary arterioles were observed using a microscope with a floating objective. In Protocol 1, AP4A (1, 10, 100 and 1,000 micromol/L) was superfused onto the heart surface before and during the superfusion of 10 micromol/L of 8-phenyltheophylline (8-PT), a P1 purinoceptor blocker. In Protocol 2, AP4A (0.1, 1, 10, and 100 nmol x kg(-1) x min(-1)) was infused into the left anterior descending coronary artery before and during the superfusion of 10 micromol/L of 8-PT. In addition to 8-PT, 30 micromol/L of pyridoxalphosphate-6-azophenyl 2',4'-disulphonic acid (PPADS), a P2X purinoceptor blocker in Protocol 3, or 300 micromol/L of N(omega)-nitro-L-arginine (LNNA) in Protocol 4, was continuously superfused, and 4 doses of AP4A were cumulatively superfused as in Protocol 1. In Protocol 5, 10 micromol/L of alpha,beta-methylene ATP, an agonist of P2X purinoceptors, was superfused for 60 min. Superfused AP4A dilated arterioles in a dose-dependent manner. The magnitude of dilatation was greater in smaller arterioles (small vessel < or = 150 microm: 24.5+/-2.2% vs large vessel > 150 microm: 10.6+/-1.5% at a dose of 1,000 micromol/L, p<0.001). On the other hand, intraluminally applied AP4A also dilated arterioles, but no size dependency was shown. In the presence of 8-PT, vasodilatory responses to superfused and intraluminally applied AP4A were attenuated and the lower doses of AP4A constricted arterioles. This vasoconstrictor effect was not affected by PPADS. The vasodilatory effect of the higher doses of AP4A was almost abolished in the presence of LNNA. Alpha,beta-methylene ATP had no effect on coronary microvascular diameters. AP4A has bidirectional effects on coronary arterial microvessels: vasodilatory effects mediated by P1 purinoceptors and NO, which might be mediated by P2Y purinoceptors, and a vasoconstrictor effect, which is not mediated by P2X purinoceptors.

Contribution of endothelium-derived relaxing factors to P2Y-purinoceptor-induced vasodilation in the isolated rat kidney

We examined the role of endothelium-derived relaxing factors nitric oxide (NO), endothelium-derived hyperpolarising factor (EDHF), and prostaglandins (PGs) to P(2Y1)- and P(2Y2)-purinoceptor-induced vasodilation in isolated rat kidney. To do it, we analysed the renal response to ATP, 2-methylthio ATP, and UTP in rat renal vasculature under normal conditions and after the administration of: N(w)-nitro-L-arginine (L-NAME), increased K(+) concentration, indomethacin, and L-NAME and increased K(+) together. Our results indicate that the vasodilator response to P(2Y1)- and P(2Y2)-purinoceptor activation in the isolated perfused kidney of rats is subserved by EDHF and NO.

Vascular imaging and intervention in peripheral arteries in the diabetic patient

Diabetic patients are four times more likely to develop peripheral vascular disease than the general population. This disease is likely to be more aggressive, with five times more patients developing critical limb ischaemia. Early diagnosis and treatment allows up to 80% of these patients to have some form of surgical or endovascular re-vascularisation. The primary imaging modalities to be used should be duplex ultrasound followed by angiography. Magnetic resonance angiography, however, holds out promise for the future as being a good method of non-invasive imaging. Endovascular (interventional radiological) procedures have a major role to play in treatment of vascular stenoses and occlusions. Thrombolytic agents can be used to dissolve thrombus within occluded vessels and so restore patency. Percutaneous transluminal angioplasty is of value in dilating the stenotic lesions within the vessels and so restoring normal blood flow. Endovascular stents may be inserted to ensure longer term patency. There is indirect evidence to suggest that the outcomes of endovascular procedures in the diabetic patient are less good than those in the general population, but nevertheless such procedures may save the diabetic patient from primary amputation and allow healing of ischaemic ulcers.

P2Y purinoceptor activation mobilizes intracellular Ca2+ and induces a membrane current in rat intracardiac neurones

1. The mobilization of Ca2+ by purinoceptor activation and the relative contributions of intra- and extracellular sources of Ca2+ were investigated using microfluorimetric measurements of fura-2 loaded in cultured neurones from rat intracardiac ganglia. 2. Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed expression of mRNA for the G protein-coupled P2Y2 and P2Y4 receptors. 3. Brief application of either 300 microM ATP or 300 microM UTP caused transient increases in [Ca2+]i of 277 +/- 22 nM and 267 +/- 39 nM, respectively. Removal of external Ca2+ did not significantly reduce these [Ca2+]i responses. 4. The order of purinoceptor agonist potency for [Ca2+]i increases was ATP = UTP > 2-MeSATP > ADP >> adenosine, consistent with the profile for P2Y2 purinoceptors. ATP- and UTP-induced rises in [Ca2+]i were completely and reversibly blocked by 10 microM PPADS (a P2 purinoceptor antagonist) and partially inhibited by 100 microM suramin (a relatively non-specific purinoceptor antagonist). 5. In the presence of the endoplasmic reticulum Ca2+-ATPase inhibitor cyclopiazonic acid (10 microM) in Ca2+-free media, the [Ca2+]i responses evoked by ATP were progressively decreased and abolished. 6. ATP- and UTP-induced [Ca2+]i rises were insensitive to pertussis toxin, caffeine (5 mM) and ryanodine (10 microM) but were significantly reduced by U-73122, a phospholipase C (PLC) inhibitor. 7. In fura-2-loaded cells, perforated patch whole-cell recordings show that ATP and UTP evoked slow outward currents at -60 mV, concomitant with the rise in [Ca2+]i, in approximately 30 % of rat intracardiac neurones. 8. In conclusion, these results suggest that in r intracardiac neurones, ATP binds to P2Y2 purinoceptors to transiently raise [Ca2+]i and activate an outward current. The signalling pathway appears to involve a PTX-insensitive G protein coupled to PLC generation of IP3 which triggers the release of Ca2+ from a ryanodine-insensitive Ca2+ store(s).

Role of A(2A)-adenosine receptor activation for ATP-mediated coronary vasodilation in guinea-pig isolated heart

1. Adenosine-5'-triphosphate (ATP) and adenosine are potent coronary vasodilators. ATP is rapidly converted to adenosine by ectonucleotidases. We examined whether coronary vasodilation caused by exogenous ATP is mediated by P(2) receptor activation or by A(2A)-adenosine receptor activation. 2. Effects of interventions on coronary conductance were determined by measuring coronary perfusion pressure in guinea-pig isolated hearts perfused at a constant flow of 10 ml min(-1). 3. ATP and adenosine both caused sustained, concentration-dependent increases of coronary conductance. Maximal responses to both agonists were equivalent. The values of pD(2) (+/-s.e.mean) for ATP and adenosine were 6.68+/-0.04 and 7.06+/-0.05, respectively. Adenosine was significantly more potent than ATP (P<0. 0001, n=10). 4. The values of pIC(50) for the selective A(2A)-adenosine receptor antagonist SCH58261 to antagonize equivalent responses to ATP and adenosine were 8.28+/-0.08 and 8.28+/-0.06 (P=0.99, n=6), respectively. 5. The non-selective adenosine receptor antagonists xanthine amine congener (XAC) and CGS15943 antagonized similarly the equivalent vasodilations caused by ATP (pIC(50) values 7.48+/-0.04 and 7.45+/-0.06, respectively) and adenosine (pIC(50) values 7. 37+/-0.13 and 7.56+/-0.11). 6. In contrast to ATP and adenosine, the two P(2) agonists 2-methylthio-ATP and uridine-5'-triphosphate failed to cause stable increases of coronary conductance, caused desensitization of vasodilator responses, and were not antagonized by SCH 58261, 8-parasulphophenyltheophylline, or XAC. 7. Glibenclamide attenuated coronary vasodilations caused by ATP and adenosine by 88 and 89%, respectively, but failed to attenuate those caused by 2-methylthio-ATP. 8. These results strongly suggest that sustained, submaximal coronary vasodilation caused by exogenous ATP is entirely mediated by adenosine acting upon A(2A)-adenosine receptors.

Seven-year outcome in the Bypass Angioplasty Revascularization Investigation (BARI) by treatment and diabetic status

OBJECTIVES

To compare seven-year survival in the Bypass Angioplasty Revascularization Investigation (BARI) patients randomly assigned to percutaneous transluminal coronary angioplasty (PTCA) versus coronary artery bypass grafting (CABG).

BACKGROUND

The primary results of BARI reported no significant difference in five-year survival between CABG and PTCA groups. However, among patients with treated diabetes mellitus, a subgroup not specified a priori, a striking difference was seen in favor of CABG.

METHODS

Symptomatic patients with multivessel disease (n = 1,829) were randomly assigned to initial treatment strategy of CABG or PTCA and followed for an average of 7.8 years. The intention-to-treat principle was used to extend the initial five-year BARI treatment comparisons.

RESULTS

Kaplan-Meier estimates of seven-year survival for the total population were 84.4% for CABG and 80.9% for PTCA (p = 0.043). This difference could be explained by the 353 patients with treated diabetes mellitus for whom estimates of seven year survival were 76.4% CABG and 55.7% PTCA (p = 0.0011). Among the remaining 1,476 patients without treated diabetes, survival was virtually identical by assigned treatment (86.4% CABG, 86.8% PTCA, p = 0.72). The PTCA group had substantially higher subsequent revascularization rates than the CABG group (59.7% vs. 13.1%, p < 0.001); however, the changes between the five- and seven-year rates were similar for the two groups.

CONCLUSIONS

At seven years, there was a statistically significant survival advantage for patients randomized to CABG compared with PTCA. Among patients with treated diabetes mellitus, the benefit of CABG over PTCA seen at five years was more pronounced at seven years; among nondiabetic patients, there was essentially no treatment difference.

Relationship of extent of revascularization with angina at one year in the Bypass Angioplasty Revascularization Investigation (BARI)

OBJECTIVES

To determine the relative degree of revascularization obtained with bypass surgery versus angioplasty in a randomized trial of patients with multivessel disease requiring revascularization (Bypass Angioplasty Revascularization Investigation [BARI]), one-year catheterization was performed in 15% of patients.

BACKGROUND

Complete revascularization has been correlated with improved outcome after coronary artery bypass grafting (CABG) but not with percutaneous transluminal coronary angioplasty (PTCA). Relative degrees of revascularization after PTCA and surgery have not been previously compared and correlated with symptoms.

METHODS

Consecutive patients at four BARI centers consented to recatheterization one year after revascularization. Myocardial jeopardy index (MJI), the percentage of myocardium jeopardized by > or =50% stenoses, was compared and correlated with angina status.

RESULTS

Angiography was completed in 270 of 362 consecutive patients (75%) after initial CABG (n = 135) or PTCA (n = 135). Coronary artery bypass grafting patients had 3+/-0.9 distal anastomoses and PTCA patients had 2.4+/-1.1 lesions attempted at initial revascularization. At one year, 20.5% of CABG patients had > or =1 totally occluded graft and 86.9% of vein graft, and 91.6% of internal mammary artery distal anastomotic sites had <50% stenosis. One year jeopardy index in surgery patients was 14.1+/-11%, 46.6+/-20.3% improved from baseline. Initial PTCA was successful in 86.9% of lesions and repeat revascularization was performed in 48.4% of PTCA patients by one year. Myocardial jeopardy index one year after PTCA was 25.5+/-22.8%, an improvement of 33.8+/-26.1% (p<0.01 for greater improvement with CABG than PTCA). At one year, 29.6% of PTCA patients had angina versus 11.9% of surgery patients, p = 0.004. One-year myocardial jeopardy was predictive of angina (odds ratio 1.28 for the presence of angina per every 10% increment in myocardial jeopardy, p = 0.002). Randomization to PTCA rather than CABG also predicted angina (odds ratio 2.19, p = 0.03).

CONCLUSIONS

In this one-year angiographic substudy of BARI, CABG provided more complete revascularization than PTCA, and CABG likewise improved angina to a greater extent than PTCA.

Utility of cardiac troponin I, creatine kinase-MB(mass), myosin light chain 1, and myoglobin in the early in-hospital triage of "high risk" patients with chest pain

OBJECTIVE

To evaluate the use of cardiac troponin I (cTnI), creatine kinase-MB(mass) (CK-MB(mass)), myosin light chain 1 (MLC 1), and myoglobin in identifying "high risk" patients with chest pain who will experience serious cardiac events (SCEs) in hospital.

DESIGN

Prospective study.

SETTING

University affiliated medical centre in Philadelphia, USA.

PATIENTS

208 patients with chest pain, at > 7% risk of acute myocardial infarction (MI), but without new ST segment elevation on their presenting ECG.

INTERVENTIONS

cTnI, CK-MB(mass), MLC 1, and myoglobin concentrations were obtained on admission (0 hour) and at 4, 8, 16, and 24 hours.

MAIN OUTCOME MEASURES

The sensitivity, specificity, positive and negative predictive value, and pre- and post-test probabilities of patients suffering an SCE in hospital were determined. SCEs included cardiac death, acute MI, cardiac arrest, life threatening cardiac arrhythmia, cardiogenic shock, and urgent coronary revascularisation.

RESULTS

Admission concentrations of all markers were poor predictors of SCEs in hospital but improved substantially at subsequent timepoints. cTnI and CK-MB(mass) were consistently the most useful prognostic indicators. If both were negative at 0, 4, and 8 hours, then 99% (95% confidence interval 96% to 100%) of patients remained free from SCEs. The only SCEs not thus predicted were revascularisation procedures and associated complications. Additional tests after 8 hours, or the inclusion of additional markers, did not improve predictive accuracy further.

CONCLUSIONS

Patients with high risk clinical features on admission who have negative cTnI and CK-MB(mass) concentrations at 0, 4, and 8 hours later have a favourable in-hospital prognosis and could be considered for early triage out of coronary care units.

Two different P2Y receptors linked to steroidogenesis in bovine adrenocortical cells

Both extracellular adenosine 5'-triphosphate (ATP) and uridine 5'-triphosphate (UTP) induced corticoid production (steroidogenesis) concentration-dependently in bovine adrenocortical cells (BA cells). Pertussis toxin (PTX, approx. 2 microg/ml) partially inhibited (approx. 55% inhibition) extracellular ATP (100 microM)-induced steroidogenesis in BA cells. However, PTX did not inhibit extracellular UTP (100 microM)-induced steroidogenesis. Both ATP- and UTP-induced steroidogeneses were significantly inhibited by suramin (50-200 microM). These effects were inhibited significantly by reactive blue-2 (more than 100 microM) and pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (more than 100 microM). Both nucleotides (1-100 microM) induced inositol phosphates accumulation and intracellular Ca2+ mobilization, but PTX did not inhibit them. The RT-PCR procedure identified only P2Y2-receptor mRNA in BA cells. These results suggest that extracellular ATP induces steroidogenesis via a unique P2 receptor linked to PTX-sensitive guanine nucleotide-binding protein (G-protein), while extracellular UTP induces steroidogenesis via P2 receptor linked to PTX-insensitive G-protein. Thus, it was concluded that at least two different P2Y-like receptors linking to steroidogenesis exist in BA cells.

Trends in coronary revascularization 1989 to 1997: the Bypass Angioplasty Revascularization Investigation (BARI) survey of procedures

Use of catheter-based and surgical coronary revascularization has steadily increased in North America. Introduction of catheter-based "new devices," including intracoronary stents, has expanded the range of patients who can be treated with percutaneous approaches. We sought to address trends in the practice of catheter-based and surgical coronary revascularization during 1989 to 1997. The 17 North American institutions participating in the NHLBI Bypass Angioplasty Revascularization Investigation (BARI) periodically completed a 5-working day survey of all surgical and catheter-based coronary revascularizations. Data collected included patient demographics, vessel disease, prior interventions, and use of new devices or minimally invasive surgical techniques. The proportion of all procedures that were catheter based (vs surgical) increased from 52.1% in 1989/1990 to 62.0% in 1997 (p <0.001). Among surgically treated patients, prevalence of prior bypass surgery decreased from 13.4% in 1989/1990 to 7.5% in 1997 (p <0.001). In 1997, 3% of surgical procedures used minimal incisions or were performed without cardiopulmonary bypass. Among patients undergoing catheter-based intervention, prevalence of left main disease increased from 2.2% to 5.7% (p <0.001), myocardial infarction within 24 hours increased from 2.4% to 9.7% (p <0.001), and prior bypass surgery increased from 16.2% to 20.8% (p = 0.056). Use of new devices increased from 11.6% of catheter-based procedures in 1990 to 67.0% in 1997 (p <0.001). Compared with the early 1990s, catheter-based revascularization is currently more commonly used for patients with acute myocardial infarction, prior bypass surgery, or severe left main narrowing. These trends are likely due to the proliferation of new devices, especially intracoronary stents, since the mid 1990s.

Intravenous hydroxyethylrutosides combined with long-term oral anticoagulation in atherosclerotic nonreconstructable critical leg ischemia: a retrospective study

OBJECTIVE

To evaluate in a group of seriously diseased patients with nonreconstructable chronic critical leg ischemia (CLI), treated by a combination of i.v. hydroxyethylrutosides (HR)* and oral anticoagulation (AC) by warfarin, the short-term effects on the cutaneous microvascular blood perfusion of the soles of feet and especially the long-term clinical outcome in terms of amputation and death.

DESIGN

A retrospective comparison between two groups of patients, HR + AC and a comparable reference group, fulfilling the same inclusion and exclusion criteria corresponding to the definition of CLI according to the Second European Consensus Document (1991). Clinical follow-up in both groups was made after 1, 3, 6, 12, and 24 months.

SETTING

Patients were examined at university departments of clinical physiology with special interest in peripheral vascular disease, in cooperation with colleagues at university departments of surgery, internal medicine and dermatology of Karolinska Hospital, Södersjukhuset and Huddinge Hospital.

PATIENTS

A total of seventy patients with CLI according to the definition of the Second European Consensus Document, 1991, ie, besides severe rest pain or ischemic lesions also a toe blood pressure < 30 mg Hg. Group with HR + anticoagulation (AC): 42 patients (19 diabetics, 23 nondiabetics). Reference group: 28 patients (18 diabetics, 10 nondiabetics). For distribution of age and toe blood pressure at baseline, see Table I.

INTERVENTIONS

Therapy group: besides ordinary standard therapy, daily HR infusions for a mean period of 3.6 weeks + oral anticoagulation continued to the end of the study at 24 months. A comparable reference group on the same basic therapy but without the combination HR + AC. PARAMETERS IN EVALUATION: Short-term parameters: clinical data, skin temperature, and fluorescein imaging. Long-term outcome: amputation or death.

RESULTS

Short-term and long-term results with HR + AC indicated that patients with severe CLI and very poor prognosis benefited in terms of survival and limb salvage from initial therapy with HR infusion combined with long-term oral anticoagulation. Results of this combined treatment seem at least comparable with those with i.v. prostacyclin analogies.

[Vascular endothelial factor (VEGF): therapeutic angiogenesis and vasculogenesis in the treatment of cardiovascular disease]

The formation of new blood vessel is essential for a variety of physiological processes like embryogenesis and the female reproduction as well as pathological processes like tumor growth, wound healing and neovascularization of ischemic tissue. Vasculogenesis and angiogenesis are the mechanisms responsible for the development of the blood vessels. While angiogenesis refers to the formation of capillaries from pre-existing vessels in the embryo and adult organism, vasculogenesis, the development of new blood vessels from in situ differentiating endothelial cells, has been previously considered restricted to embryogenesis. Recent investigations, however, show the existence of endothelial progenitor cells (EPCs) in the peripheral blood of the adult and their participation in ongoing neovascularization. Molecular and cell-biological experiments suggest that different cytokines and growth factors have a stimulatory effect on these bone-marrow derived EPCs. Results with GM-CSF (granulocyte macrophage-colony stimulating factor) and VEGF (vascular endothelial growth factor) open a new insight into the clinical use of cytokines and in particular the use of growth factors in gene therapy. The administration via protein or plasmid-DNA for neovascularization seems to enhance both pathways, angiogenesis and vasculogenesis.

Relaxant effect of 2-methyl-thio-adenosine diphosphate on rat thoracic aorta: effect of clopidogrel

The main aim of this study was to determine the functional effect of 2-methyl-thio-adenosine diphosphate (2MeS-ADP) on vascular purinoceptors, in comparison with that of a characterised agonist of the P2Y1 receptor, 2-methyl-thio-adenosine triphosphate (2MeS-ATP), and of the P2Y2 receptor, uridine triphosphate (UTP). On phenylephrine-precontracted rat aortic rings, mounted isometrically in organ baths, we found that 2MeS-ADP (10(-9) to 10(-6) M) induced concentration-dependent relaxation of rings with a functional endothelium. Mechanical removal of the endothelium abolished the relaxant effect of 2MeS-ADP. The 2MeS-ADP-induced relaxation of phenylephrine-precontracted rings was inhibited by Nomega-nitro-L-arginine methyl ester (L-NAME) (100 microM) but not by indomethacin (100 microM) or aspirin (1 mM), indicating that the 2MeS-ADP-induced relaxation was nitric oxide (NO) synthase-mediated but not cyclooxygenase-dependent. Repeated stimulation with 2MeS-ADP resulted in desensitisation of the receptor. Under these conditions, the relaxant effect of 2MeS-ATP was abolished. On the contrary, UTP-induced relaxation was not affected, showing that 2MeS-ADP and 2MeS-ATP but not UTP shared the same receptor. Suramin (100 microM), a non-specific P2 inhibitor, abolished the effect of 2MeS-ADP, 2MeS-ATP and UTP. In contrast, pyridoxal-phosphate-6-azophenyl-2'-4'-disulphonic acid (PPADS) and adenosine-3'-phosphate-5'-phosphosulphate (A3P5PS) abolished only the vasodilator responses to 2MeS-ADP and 2MeS-ATP and did not affect the relaxant effect of UTP, showing that 2MeS-ADP acted through the P2Y1 receptor. Clopidogrel, a potent platelet ADP receptor antagonist, at a dose that strongly inhibited ADP-induced platelet aggregation ex vivo, did not modify the relaxant responses to 2MeS-ADP or 2MeS-ATP. In conclusion, these results showed that 2MeS-ADP induces endothelium-dependent, NO-mediated relaxation of rat aortic rings. This effect, resistant to clopidogrel treatment, occurred through activation of the P2Y1 receptor.

The effects of iloprost infusion on microcirculation is independent of nitric oxide metabolites and endothelin-1 in chronic peripheral ischaemia

BACKGROUND

Endothelial vascular tone modulators are thought to be involved in aetiopathogenesis of systemic sclerosis (SS) and of peripheral artery occlusive disease (PAOD). Iloprost, a prostacyclin (PGI2) analogue, induces clinical benefit in patients suffering from peripheral ischaemia. This study was performed to investigate the effect of this drug on endothelial function in vivo to elucidate the role of vascular tone modulators.

METHODS

Fourteen PAOD and 15 SS patients were treated for 24 and 10 days respectively. On the first day, before and after therapy, nitric oxide metabolites (NO2-/NO3-) and endothelin-1 (ET-1) plasma concentrations were detected; moreover, the endothelium-dependent vasodilatation in response to artificial ischaemia was evaluated by means of an echo-Doppler device.

RESULTS

The echo-Doppler evaluation showed that the percentage of arterial reactive dilatation was not modified by placebo or by iloprost, and that the increase in blood velocity flow lasted for a significant longer time after drug infusion (226.79 +/- 17.49 vs. 310.71 +/- 36.32 s; P > 0.04). NO2-/NO3- and ET-1 plasma concentration were higher in patients than in control subjects (P < 0.004). After 6 h of iloprost infusion, no significant modifications were detected.

CONCLUSION

This study provides evidence that iloprost enhances the microvascular functional capacity and clinical benefit for patients. The effects of the drug seem to be independently or not directly correlated with its interactions with vascular tone modulators such as NO2-/NO3- or ET-1.

Fibrinogen and mortality in chronic critical limb ischaemia

OBJECTIVE

Plasma fibrinogen predicts cardiovascular events in patients with stable peripheral arterial occlusive disease, but its predictive value in patients with chronic critical limb ischaemia, a condition associated with a high risk of death, is unknown.

DESIGN

A prospective cohort study.

SETTING

Determination of fibrinogen and other potential predictors during clinic-based work-up of patients admitted for diagnostic and therapeutic evaluation.

SUBJECTS

A total of 108 patients (72 +/- 10 years, 78 males) with atherosclerotic occlusive disease and critical limb ischaemia (pain at rest and/or trophic lesions) followed up for a median period of 1.6 years). (range: 8 days-5.5 years; 218 patient-years).

MAIN OUTCOME MEASURES

Total mortality.

RESULTS

Forty-five deaths (71% cardiovascular) occurred during the follow-up. Baseline fibrinogen was higher in those who died in the early follow-up period (first 6 months), as were white cell count and serum creatinine, while haematocrit was lower. Plasma fibrinogen values correlated positively with white cell count, and negatively with haematocrit; other cardiovascular prognostic factors did not differ. Only plasma fibrinogen predicted survival independently in multivariate age-corrected Cox regression analysis. Relative risk of death doubled for each standard deviation above the mean and increased with each tertile increase in fibrinogen.

CONCLUSIONS

Fibrinogen predicted death in these elderly arteriopaths with critical limb ischaemia, particularly those who died in the first months following critical ischaemia. Inflammatory stimuli secondary to severely defective tissue oxygenation and possibly sepsis and necrosis, might have stimulated fibrinogen, an acute-phase reactant, thereby compromising organ perfusion through increased blood viscosity and/or promoting thrombosis.

Prevalence of hibernating myocardium in patients with severely impaired ischaemic left ventricles

OBJECTIVE

Severe impairment of left ventricular (LV) contraction is associated with an adverse prognosis in patients with ischaemic heart disease. Revascularisation may improve the impaired LV contraction if hibernating myocardium is present. The proportion of patients likely to benefit from this intervention is unknown. Therefore, the prevalence of hibernating myocardium in patients with ischaemic heart disease and severe impairment of LV contraction was assessed.

DESIGN

From a consecutive series of patients undergoing coronary angiography for the investigation of chest pain or LV impairment, all patients with ischaemic heart disease and an LV ejection fraction (LVEF) < or = 30% were identified. These patients underwent positron emission tomography (PET) to detect hibernating myocardium, identified by perfusion metabolism mismatch.

SETTING

A teaching hospital directly serving 500,000 people.

RESULTS

Of a total of 301 patients, 36 had ischaemic heart disease and an LVEF < or = 30%. Twenty-seven patients had PET images, while nine patients were not imaged because of emergency revascularisation (three), loss to follow up (one), inability to give consent (four), and age < 50 years (one, ethics committee guidelines). Imaged and non-imaged groups were similar in LV impairment, demographic characteristics, and risk factor profile. Fourteen patients (52% of the imaged or 39% of all patients with ischaemic heart disease and LVEF < or = 30%) had significant areas of hibernating myocardium on PET.

CONCLUSION

It is possible that up to 50% of patients with ischaemic heart disease and severely impaired left ventricles have hibernating myocardium.

Role of orthotopic heart transplantation in the management of patients with recurrent ventricular tachyarrhythmias following myocardial infarction

OBJECTIVE

To report the outcome of an intention to treat by heart transplantation strategy in two groups of patients after infarction, one with both left ventricular failure (LVF) and ventricular tachyarrhythmias (VTA) (group A) and the other with progressive LVF following antiarrhythmic surgery for VTA (group B).

PATIENTS AND METHODS

Group A comprised 17 consecutive patients for whom transplantation was considered the best primary non-pharmacological treatment; group B comprised five consecutive patients assessed and planned for transplantation after antiarrhythmic surgery.

RESULTS

In group A, eight patients underwent transplantation and all survived the first 30 day period. At median follow up of 55 months (range 11 to 109) seven of this subgroup were still alive. Five patients died of recurrent VTA before transplantation, despite circulatory support. In the face of uncontrollable VTA, four of these underwent "high risk" antiarrhythmic surgery while awaiting transplantation: three died of LVF within 30 days and one was saved by heart transplantation two days after arrhythmia surgery. Mortality for the transplantation strategy in group A patients was 47% by intention to treat analysis. Quality of life in the eight actually transplanted, however, was good and only one died during median follow up of 56 months. The five patients in group B were accepted for transplantation for progressive LVF at a median of 21 months (range 12 to 28) after antiarrhythmic surgery. One died of LVF before transplantation, 22 months after initial surgery; another died of high output LVF three days after transplantation. Thus mortality of the intended strategy was 40%. The three transplanted patients are alive and well at 8-86 months.

CONCLUSIONS

Although the short and medium term outcome in category A or B patients who undergo transplantation is good, the overall success of the transplantation strategy in category A patients is limited by lack of donors in the short time frame in which they are required.

Purinoceptors mediate renal vasodilation by nitric oxide dependent and independent mechanisms

BACKGROUND

Adenosine triphosphate (ATP) and its metabolites including adenosine modulate renal vascular tone under physiological and pathophysiological conditions. Their effects are brought about by activation of membrane bound P1- and P2-purinoceptors located on smooth muscle and endothelial cells. In this study we analyzed the purinoceptor mediated dilation of rabbit and human renal arteries, and evaluated the possible involvement of endothelium-derived relaxing factors.

METHODS

Segments of rabbit and human renal arteries were incubated and perfused with medium containing indomethacin. After preconstriction, drug induced changes in the vessel diameters were measured by a photoelectric device.

RESULTS

ATP (EC50 = 1 mumol/liter), added intraluminally, caused maximal vasodilation of 80 to 100% of the preconstriction response in both species. This effect was inhibited by the P1-purinoceptor antagonist 8-p-(sulphophenyl)theophylline (100 mumol/liter), suggesting that it was in part due to breakdown of ATP to adenosine. The nature of purinoceptor mediated renal vasodilation was studied further in rabbit renal arteries. Adenosine (EC50 = 1 mumol/liter) as well as the P2Y-receptor agonists ADP beta S (EC50 = 0.4 mumol/liter) and 2-MeSATP (EC50 = 0.2 mumol/liter) dilated the arteries by 80 to 100%. The effects of 2-MeSATP, which were to a much lesser extent that of ADP beta S but not that of adenosine, were attenuated by the P2Y-antagonist reactive blue 2 (3 mumol/liter). Removal of the endothelium almost abolished the vasodilation induced by adenosine and ATP. In contrast, these dilator response were only slightly attenuated by the nitric oxide synthase blockers NG-nitro-L-arginine methyl ester and NG-nitro-L-arginine (300 mumol/liter each), whereas acetylcholine and 2-MeSATP induced dilation was markedly reduced by NG-nitro-L-arginine methyl ester.

CONCLUSIONS

P1-purinoceptors activated by adenosine dilate rabbit renal arteries by an endothelium-derived relaxing factor that appears to be distinct from nitric oxide. In contrast, P2Y-purinoceptor induced renal dilation is mediated by nitric oxide. ATP, the physiological activator of P2Y-purinoceptors, is rapidly broken down to adenosine in rabbit and human renal arteries. Therefore, in rabbit and human renal arteries the vasodilatory effect of exogenous ATP mainly results from P1-purinoceptor activation probably through its breakdown product, adenosine.

Receptors involved in nerve-mediated vasoconstriction in small arteries of the rat hepatic mesentery

1. We have investigated the neurotransmitters and receptor subtypes involved in nerve-mediated vasoconstriction in small arteries of the rat hepatic mesentery. 2. A dense sympathetic innervation was demonstrated using catecholamine histochemistry and antibodies against the synaptic vesicle protein synaptophysin. 3. Reverse transcription-polymerase chain reaction (RT-PCR) demonstrated very strong expression of the alpha1A-adrenergic, neuropeptide Y (NPY) Y1, P2X1- and P2X4-purinergic receptors, moderate expression of the alpha2B-adrenergic receptor and the purinergic P2X5- and P2X7-receptors and weak expression of the alpha1B-, alpha1D-, alpha2A- and alpha2C-adrenergic receptors and the P2X2- and P2X3-purinergic receptors. NPY2 and P2X6 receptor expression was absent. 4. Electrical field stimulation (10 Hz, 10 s) produced contractions which were abolished by tetrodotoxin (10(-6) M) and/or guanethidine (GE, 5 x 10(-6) M) and a combination of benextramine (10(-5) M) and alpha,beta-methylene ATP, (alpha,beta-mATP, 3 x 10(-6) M) or PPADS (10(-5) M). Selective alpah1-adrenergic receptor antagonists showed the potency order of prazosin > WB-4101 > 5-methyl-urapidil > BMY 7378. Yohimbine (10(-8) M, 10(-7) M), alpha,beta-mATP (3 x 10(-6) M) and PPADS (10(-5) M) each enhanced the response to nerve stimulation. 5. Some experiments demonstrated a slow neurogenic contraction which was abolished by GE or the selective NPY1 receptor antagonist 1229U91 (6 x 10(-7) M). 6. We conclude that nerve-mediated vasoconstriction results from the activation of postsynaptic alpha,beta-adrenergic and P2X-purinergic receptors and under some conditions, NPY1 receptors. Neurotransmitter release is modulated by presynaptic alpha2-adrenergic receptors and possibly also P2X-purinoceptors. The major postsynaptic subtypes involved were well predicted by mRNA expression as measured by RT-PCR, suggesting that this technique may be a useful adjunct to studies aimed at identifying functional receptor subtypes.

Phenotype changes of the vascular smooth muscle cell regulate P2 receptor expression as measured by quantitative RT-PCR

Studies using selective agonists have suggested that the contractile effect of extracellular nucleotides, such as ATP and UTP, in blood vessels is mediated mainly by P2X1 receptors with a smaller contribution of P2Y receptors while the mitogenic effect is mediated by P2Y (P2Y1, P2Y2, P2Y4, and P2Y6) receptors with no effect of P2X1 receptors. This indicates a difference in P2 receptor expression between the contractile and the synthetic phenotype of the SMC. To measure the expression of mRNA for these receptors a competitive RT-PCR assay was developed that utilised synthetic RNA-competitors allowing determination of the number of mRNA copies for each receptor in the samples. In the synthetic phenotype the mitogenic P2Y1 and P2Y2 receptor transcripts were upregulated by 342- and 8-fold, respectively, while the contractile P2X1 receptor is totally downregulated and the P2Y4 and P2Y6 receptors were unchanged. This plasticity of the receptor expression may be important in the transition from the contractile to the synthetic SMC phenotype.

Specific activation of adenylyl cyclase V by a purinergic agonist

The present study was designed to investigate whether and how the purinergic stimulation of rat ventricular myocytes modulates the cAMP-dependent pathway. Stimulation of cardiomyocytes with ATPgammaS in the presence of the phosphodiesterase inhibitor IBMX increases by 3-fold intracellular cAMP content. In contrast to beta-adrenergic stimulation, the purinergic stimulation of adenylyl cyclase was not inhibited by activation or enhanced by inhibition of a Gi protein. Forskolin did not potentiate the effect of extracellular ATPgammaS on intracellular cAMP content but the effect of isoproterenol did. Like isoproterenol, the purinergic agonist decreased subsequent ADP-ribosylation of a 45 kDa G(alpha s) by cholera toxin. ATPgammaS also increased cAMP content in neonatal rat cardiomyocytes, a cell type that expresses a long form of Gs protein (alpha(s), 52 kDa) in contrast to adult rat cardiomyocytes that express mostly a short form of Gs protein (alpha(s), 45 kDa). Both purinergic and beta-adrenergic agonists increased cAMP in HEK 293 cells expressing type V adenylyl cyclase while cAMP was only increased by beta-adrenergic stimulation of HEK expressing type IV or VI adenylyl cyclases. Thus, we propose that the purinergic and beta-adrenergic stimulations differentially activate adenylyl cyclase isoforms in rat cardiomyocytes and that adenylyl cyclase V is the specific target of the purinergic stimulation.

Extracellular ATP: a growth factor for vascular smooth muscle cells

1. Extracellular adenosine triphosphate (ATP) is mitogenic for vascular smooth muscle cells (VSMC) and stimulates several events that are important for cell proliferation: DNA synthesis, protein synthesis, increase of cell number, immediate early genes, cell-cycle progression, and tyrosine phosphorylation. 2. Receptor characterization indicates mitogenic effects of both P2U and P2Y receptors. The P2X receptor is lost in cultured VSMC and is not involved. Several related biological substances such as UTP, ITP, GTP, AP4A, ADP, and UDP are also mitogenic. 3. Signal transduction is mediated via Gq-proteins, phospholipase C beta, phospholipase D, diacyl glycerol, protein kinase C alpha, delta, Raf-1, MEK, and MAPK. 4. ATP acts synergistically with polypeptide growth factors (PDGF, bFGF, IGF-1, EGF, insulin) and growth factors acting via G-protein-coupled receptors (noradrenaline, neuropeptide Y, 5-hydroxytryptamine, angiotensin II, endothelin-1). 5. The mitogenic effects have been demonstrated in rat, porcine, and bovine VSMC and cells from human coronary arteries, aorta, and subcutaneous arteries and veins. 6. The trophic effects on VSMC and the abundant sources for extracellular ATP in the vessel wall make a pathophysiological role probable in the development of atherosclerosis, neointima-formation after angioplasty, and possibly hypertension.

The pentoxifylline experience: exercise testing reconsidered

This paper critically reviews the methodology used in clinical trials in chronic occlusive arterial disease (COAD) stage II (intermittent claudication) patients. The reasons for choosing internationally accepted standard treadmill settings as well as its limitations are discussed. Emphasis is put on the discussion of valid trial endpoints such as hemodynamic surrogates and clinically oriented parameters. Reasons for a spontaneous and treatment-unrelated improvement in claudication distance are elucidated, and variables which may be used for the definition of patient subsamples showing a high frequency of a pronounced treatment response (treatment responder populations) are presented. The magnitude of claudication distance improvement that might be considered clinically relevant is discussed in the light of the European Union guidelines for clinical trials in COAD patients. Results achieved with pentoxifylline are presented in context with all variables mentioned above.

The pathophysiology of peripheral arterial disease: rational targets for drug intervention

The most common cause of peripheral arterial disease (PAD) is atherosclerosis, which begins with an alteration in endothelial biology due to hypercholesterolemia, diabetes mellitus, hypertension, tobacco use, elevated levels of lipoprotein(a) or homocystinemia. With chronic and severe arterial disease, changes begin to occur in the microcirculation, including obstruction at the microvascular level and tissue injury. Based on insights into the vascular biology of PAD, new therapies have been developed and are at various stages of clinical trials. Future pharmacotherapy for PAD will include agents that have one or more of the following attributes; (1) reduce, or even reverse, the progression of atherosclerosis; (2) inhibit plaque rupture; (3) inhibit thrombosis by a novel mechanism; (4) induce angiogenesis; (5) reverse microvascular derangements; (6) affect blood rheology; and (7) enhance skeletal muscle's ability to use available nutrients.

The challenge and importance of defining critical limb ischemia

Patients with critical limb ischemia are at risk of limb loss and have very high cardiovascular and total mortality rates, which are greater than can be accounted for by the usual risk factors for atherosclerosis. A definition of critical ischemia is necessary to determine the natural history of the disease and to assess and compare the efficacy of various forms of therapy. The definition needs to be based on hemodynamic criteria because clinical manifestations and outcomes are not reliable. The reasons for the difficulties in arriving at a generally acceptable definition are explored. Building on the previous work of others, modified hemodynamic definitions for critical and subcritical ischemia, which include measurements of pressures and of indices of microcirculation, are proposed.

Adenosine triphosphate causes vasospasm of the rat femoral artery

OBJECTIVE

Adenosine 5'-triphosphate (ATP) causes vasoconstriction by activation of P2-purinoceptors on vascular smooth muscle cells. Erythrocytes contain ATP at a concentration (1.6 mmol/L) that contracts smooth muscle. Previous studies of hemoglobin solutions did not assess whether the vasoactivity was caused by ATP rather than or in addition to hemoglobin. It was hypothesized that the hemolysis of erythrocytes that occurs after subarachnoid hemorrhage releases ATP in concentrations that cause vasospasm.

METHODS

Thirty-eight rats were randomly assigned to undergo placement of one of the following compounds in a silastic elastomer cuff around each femoral artery: 1) agarose gel (n = 8); 2) dog erythrocyte hemolysate (n = 8); 3) purified human hemoglobin (Hemolink; Hemosol, Inc., Toronto, Canada; n = 8); 4) ATP (n = 8); or 5) clotted autologous blood (n = 6). The amounts of hemoglobins and adenine nucleotides in the compounds were measured by spectrophotometry and high pressure liquid chromatography. Hemolysate, purified hemoglobin, and ATP were mixed with agarose gel to create an artificial clot. Rats were killed and fixed by perfusion at physiological blood pressure 7 days after perivascular cuff and spasmogen placement. Vasospasm was assessed by image analysis of cross sections of fixed femoral arteries. Arteries were assessed for histopathological changes on 3-point scales.

RESULTS

There was significant variance in arterial diameters among groups (mean diameter +/- standard deviation: agarose gel, 0.29 +/- 0.06; purified hemoglobin, 0.28 +/- 0.04; hemolysate, 0.24 +/- 0.05; ATP, 0.25 +/- 0.05; clotted blood, 0.24 +/- 0.01; P < 0.05, analysis of variance, n = 11-20). Animals exposed to clotted blood, hemolysate that contained ATP, or ATP, developed vasospasm, whereas purified hemoglobin and agarose did not cause vasospasm. Endothelial proliferation and perivascular inflammation were more severe (P < 0.05) in arteries exposed to clotted blood, purified hemoglobin, and hemolysate.

CONCLUSION

These results suggest that ATP may be a vasospastic substance released by erythrocyte hemolysis. The concentration of ATP in impure solutions of hemoglobin is too low to account for the vasoactivity of these solutions. The discrepancy between arterial narrowing and histopathological changes suggests that either histopathological changes may not be an important correlate of arterial vasospasm or that other substances are important in vasospasm.

Dependence of P2-nucleotide receptor agonist-mediated endothelium-independent relaxation on ectonucleotidase activity and A2A-receptors in rat portal vein

1. The mechanism of action of P2 nucleotide receptor agonists that produce endothelium-independent relaxation and the influence of ecto-ATPase activity on this relaxing effect have been investigated in rat portal vein smooth muscle. 2. At 25 degrees C, ATP, 2-methylthioATP (2-MeSATP) and 2-chloroATP (2-ClATP), dose-dependently inhibited spontaneous contractile activity of endothelium-denuded muscular strips from rat portal vein. The rank order of agonist potency defined from the half-inhibitory concentrations was 2-CIATP (2.7+/-0.5 microM, n=7) >ATP (12.9+/-1.1 microM, n=9) > or =2-MeSATP (21.9+/-4.8 M, n=4). In the presence of alphabeta-methylene ATP (alphabeta-MeATP, 200 microM) which itself produced a transient contractile effect, the relaxing action of ATP and 2-MeSATP was completely abolished and that of 2-ClATP strongly inhibited. 3. The non-selective P2-receptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS, 100 microM) did not affect the relaxation induced by ATP, 2-MeSATP, and 2-ClATP. 4. The A2A-adenosine receptor antagonist ZM 241385 inhibited the ATP-induced relaxation in a concentration-dependent manner (1-100 nM). In the presence of 100 nM ZM 241385, the relaxing effects of 2-MeSATP and 2-ClATP were also inhibited. 5. ADP, AMP and adenosine also produced concentration-dependent inhibition of spontaneous contractions. The relaxing effects of AMP and adenosine were insensitive to alphabeta-MeATP (200 microM) but were inhibited by ZM 241385 (100 nM). 6. Simultaneous measurements of contraction and ecto-ATPase activity estimated by the degradation of [gamma-32P]-ATP showed that muscular strips rapidly (10-60 s) hydrolyzed ATP. This ecto-ATPase activity was abolished in the presence of EDTA and was inhibited by 57+/-11% (n=3) by 200 microM alphabeta-MeATP. 7. These results suggest that ATP and other P2-receptor agonists are relaxant in rat portal vein smooth muscle, because ectonucleotidase activity leads to the formation of adenosine which activates A2A-receptors.

Action of Al-ATP on the isolated working rat heart

ATP is an important extracellular messenger in the coronary vasculature of the heart. To be effective its extracellular concentration must be tightly controlled and this is achieved via ectonucleotidases located in the luminal surface of the coronary endothelium. Al-ATP is a potent inhibitor of the hydrolysis of ATP and we speculated that Al-ATP released by cells into the blood would disrupt the signalling function of extracellular ATP. We tested this hypothesis by perfusing isolated working Wistar rat hearts with buffers containing either ATP or Al-ATP. The functional parameters measured were, coronary flow, heart rate and pulsatile power. A number of control perfusions including adenosine, ATP-gamma-S and Al were used to identify those effects which might be specific to ATP and Al-ATP. Al-ATP did not appear to inhibit the function of the endothelial ectonucleotidases. Both ATP and Al-ATP produced a significant increase in coronary flow and this could be attributed to a coronary vasodilation. Interestingly, whilst the effect of ATP was reversible that of Al-ATP was not. ATP caused a reduction in heart rate which was potentiated by aluminium. The negatively chronotropic effect of Al-ATP was mediated via a mechanism which was either distinct from or in addition to the similar response known to be caused by adenosine. We have demonstrated for the first time an influence of Al-ATP on heart function. Perhaps more pertinently we present the first evidence that Al-ATP may influence the function of ATP-specific receptors.

A novel phospholipase C- and cAMP-independent positive inotropic mechanism via a P2 purinoceptor

Although ATP, acting through a P2 purinoceptor, can stimulate a pronounced positive inotropic effect in cardiac ventricular myocytes, the receptor-effector mechanism that underlies this stimulatory cardiac action is not well understood. The objectives of the present study were to develop the cultured chick embryo ventricular myocytes as a novel model for the cardiac P2 purinoceptor and to determine the mechanism underlying its positive inotropic effect. ATP caused an 89 +/- 8.9% (n = 14 cells) increase in the myocyte contractility, with an efficacy and potency order of ATP > ADP > AMP >> adenosine. 2-Methylthio-ATP (2-MeS-ATP) but not alpha,beta-methylene-ATP was able to stimulate myocyte contractility, with a maximal increase of 54 +/- 2.6% (n = 11 cells). Although UTP potently stimulates phosphoinositide hydrolysis, it had an only modest positive inotropic effect (27 +/- 7% maximal increase; n = 8 cells). In contrast to previous suggestions, the 2-MeS-ATP-stimulated positive inotropic response does not require the action of phospholipase C (PLC), such as that of the inositol phosphates; the UTP effect on contractility appears to be mediated via the 2-MeS-ATP-sensitive P2 receptor. The PLC inhibitor U-73122 had no effect on the 2-MeS-ATP-stimulated increase in contractility, providing further evidence against a role for PLC in the inotropic effect of 2-MeS-ATP. An adenosine 3',5'-cyclic monophosphate-independent Ca2+ entry-stimulating mechanism appears to underlie a direct coupling of the receptor to stimulation of the myocyte contractility. This new PLC- and adenosine 3',5'-cyclic monophosphate-independent positive inotropic mechanism represents a target for developing novel positive inotropic therapeutics.

Clinical characteristics and outcome in 223 diabetic patients with deep foot infections

Clinical characteristics and outcome in 223 consecutive diabetic patients with deep foot infections are reported. Patients were treated by a multidisciplinary diabetic foot-care team at the University Hospital, Lund, Sweden, and were prospectively followed until healing or death. About 50% of patients lacked clinical signs of infection, such as a body temperature > 37.8 degrees C, a sedimentation rate > 70 mm/hour, and white blood cell count (WBC) > 10 x 10(9)/liter. Eighty-six percent had surgery before healing or death. Thirty-nine percent healed without amputation; 34% healed after a minor and 8% after a major amputation. Sixteen percent were unhealed at death, and 3% were unhealed at the end of the observation period. Of those unhealed at death or follow-up, 4 patients had had a major and 11 a minor amputation. After correction for age and sex, duration of diabetes < 14 years, palpable popliteal pulse, a toe pressure > 45 mmHg, and an ankle pressure > 80 mm Hg, absence of exposed bone and a white blood cell count < 12 x 10(9)/liter were all related to healing without amputation in a logistic regression analysis. We conclude that although only 1 in 10 had a major amputation, nearly all diabetic patients with a deep foot infection needed surgery and more than one third had a minor amputation before healing or death in spite of a well-functioning diabetic foot-care team responsible for all included patients.

Integrative and interactive studies of the cardiac system: deciphering the cardionome

The cardiac system, denoted as the Cardionome, represents one of the most exciting challenges to human ingenuity. Critical to our survival, it consists of a tantalizing array of interacting phenomena, from ionic transport, membrane channels and receptors through cellular metabolism, energy production, fiber mechanics, microcirculation, and electrical activation to the clinically observed global functions. These are measured by pressure, volume, shape, coronary flow, heart rate, and other changes. It is a complex interactive system requiring the intense efforts of capable scientists in the life sciences, including medicine, exact sciences, engineering and biomedical technology devoted to address these multivariable, multidisciplinary challenges, so as understand and control the pathologies involved. Here we present some of our past interactive studies and highlight two new models, one demonstrating micro to macro integration, and one involving tissue-organ interaction of various parameters. These models yield new insights into cardiac performance.

Cardiac cephalgia: a treatable form of exertional headache

We report two patients with exertional headaches beginning with vigorous exercise and relieved by rest. Neurologic evaluation and neuroimaging were normal in both. During exercise stress testing, the onset of the patients' typical headaches correlated with ECG changes indicative of myocardial ischemia. In both patients coronary angiography revealed three-vessel disease, and myocardial revascularization procedures were followed by complete resolution of headaches. Based on these patients, and a review of prior similar reports, we conclude that myocardial ischemia is a rare and treatable cause of exertional headache. Accurate diagnosis is critical to controlling headaches and preventing myocardial infarction.

Chromosomal localization of the human P2y6 purinoceptor gene and phylogenetic analysis of the P2y purinoceptor family

The G-protein-coupled P2Y purinoceptors mediate a variety of physiological effects in response to extracellular nucleotides. With the recent discovery of several new members from a variety of species, the P2Y purinoceptor family now encompasses types P2Y1 to P2Y6. By fluorescence in situ hybridization and utilization of the National Center for Biotechnology Information (NCBI) database, the human P2Y6 gene was localized to chromosome 11q13.5, between polymorphic markers D11S1314 and D11S916. NCBI database analysis of the remaining human P2Y purinoceptor genes revealed that P2Y2 and P2Y6 mapped to within less than 4 cM, and thus constitute the first described chromosomal clustering of this gene family. Phylogenetic analysis of the P2Y purinoceptor family demonstrated the presence of five evolutionary branches and suggests the occurrence of an ancient gene duplication event.

The effects of P2 purinoceptor agonists on the isolated portal vein of the guinea pig

UTP, ATP and several of its analogues enhanced contractions of the longitudinal smooth muscle layer of the guinea-pig portal vein. The rank order of potency was 2-methylthioATP > alpha, beta-methyleneATP > adenosine tetraphosphate > or = beta, gamma-methyleneATP > or = ATP = UTP > > adenosine. Suramin (100 microM) blocked the contractile effects of 2-methylthioATP and alpha,beta-methyleneATP, but not those of ATP and adenosine tetraphosphate. The P1 purinoceptor antagonist, 8-phenyltheophylline (10 microM), was without effect on the response to ATP. Field stimulation (5 s trains every 100 s, 1 ms, 55 V) caused frequency-dependent contractions that were partially reduced by the noradrenergic neurone blocking drug; BW 172C58 (4-benzoyl-xylocholine, 10 microM), but not by suramin. alpha,beta-MethyleneATP was more potent than beta,gamma-methyleneATP, UTP and adenosine tetraphosphate in partially inhibiting field stimulation-induced contractions of the portal vein; its effects, but not those of adenosine tetraphosphate, were reduced by suramin. These results indicate that the guinea-pig portal vein contains P2 purinoceptors; these include a P2x subtype, mediating contraction.

Elevated levels of basic fibroblast growth factor in patients with limb ischemia

Basic fibroblast growth factor (bFGF), a prototypic member of a family of heparin-binding growth factors, is angiogenic both in vitro and in vivo. Increased levels and activity of bFGF have been documented in a variety of diseases, including tumors. We sought to determine whether bFGF might be similarly elevated in patients with clinical evidence of limb ischemia. Serum was obtained at the time of percutaneous revascularization from patients with symptomatic peripheral vascular disease (46 procedures were performed on 40 patients). An enzyme-linked immunoassay specific for bFGF was used (limit of detection, 1 pg/ml; range in normal subjects, 0 to 5 pg/ml). Among the 40 patients (28 men, 12 women, mean age 70 years) studied, elevated circulating bFGF (> or = 10 pg/ml) was detected in 36 samples (78%); levels ranged from 10 to 310 pg/ml (mean +/- SEM = 62 +/- 12). In 16 (89%) of 18 patients with both rest pain and nonhealing ischemic ulcers, serum bFGF levels were elevated up to 30 times normal values. In conclusion, circulating levels of bFGF are elevated in patients with vascular insufficiency and may reflect a physiologic response to limb ischemia.

Effect of P2-purinoceptor antagonists on hemolysate-induced and adenosine 5'-triphosphate-induced contractions of dog basilar artery in vitro

OBJECTIVE

To test the hypothesis that the vasoactive effects of hemolysate of dog erythrocytes on dog basilar artery in vitro are caused by adenosine 5'-triphosphate (ATP).

METHODS

Dog erythrocyte hemolysate was assayed for ATP by high-pressure liquid chromatography. Dog basilar arteries were cut into rings and studied under isometric tension to determine the effects of the P2-purinoceptor antagonists suramin, pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid, and reactive blue 2 on contractions induced by hemolysate, prostaglandin F2 alpha (PGF2 alpha), KCl, uridine 5'-triphosphate, and ATP.

RESULTS

Dog erythrocyte hemolysate contained 34 mumol/L of ATP. Hemolysate produced concentration-dependent contractions of dog basilar artery. Suramin (100 mumol/L) significantly inhibited contractions to hemolysate, ATP, and uridine 5'-triphosphate but not to PGF2 alpha and KCl (P < 0.05). Pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid (100 mumol/L) caused a small but significant reduction of the contractions to hemolysate and did not affect contractions to PGF2 alpha and KCl. Reactive blue 2 (30 mumol/L) produced significant inhibition of contractions to hemolysate and PGF2 alpha but did not affect contractions to KCl.

CONCLUSION

These findings suggest that ATP mediates a smooth muscle contractile response of hemolysate on dog basilar artery. Because erythrocyte cytosol is known to be important in the pathogenesis of vasospasm, these results suggest that ATP may contribute to the vasoconstriction that occurs in vasospasm.

Operations, total hospital stay and costs of critical leg ischemia. A population-based longitudinal outcome study of 321 patients

In a longitudinal analysis of all 321 patients in a defined population having surgery for critical leg ischemia during 1 year in Malmöhus county (0.53 million inhabitants), Sweden, we investigated all vascular procedures and amputations on both legs, total hospital stay and hospital costs from the first procedure in each patient until death or at follow-up at least 6 years postoperatively. The first (key) operation during the inclusion year was a reconstructive vascular procedure in 96 patients, a restorative vascular procedure in 111 and a major amputation in 114 patients. One third of those with a reconstructive and half of those with a restorative key procedure had an ipsilateral major amputation. The mean number of surgical procedures and length of hospital stay among all patients were 3 (1-19) procedures and 117 (1-1097) days, respectively. Of the total number of days in hospital, less than half were in surgical departments, 10% in other acute-care departments and almost half in rehabilitation clinics and nursing homes. The total hospital and surgical costs among all patients were USD 15.1 million (mean USD 47,000/patient), with no significant differences in relation to the key operation. We conclude that patients who have undergone surgery for critical leg ischemia accumulate very high total long-term hospital costs due to the need for repetitive surgery and long hospital stays. Our findings also show that a longitudinal study, including hospital stay in departments other than surgical, is necessary for a correct cost-and-outcome analysis.