Effects of alprostadil on blood rheology and nucleoside metabolism in patients affected with lower limb chronic ischaemia.

The acute (0.57 microg/kg i.v. in 2 hours) and long-term (0.57 microg/kg i.v. in 2 hours for 5 days over 4 weeks) effects of the PGE1 analogue alprostadil were studied in patients affected with intermittent claudication. Whole Blood Viscosity (WBV), Whole Blood Filterability (WBF), haematocrit (Htc) and fibrinogen plasma concentration, were studied together with P50, 2,3-diphosphoglycerate, and adenosine plasma levels. Moreover, in the long-term study, pain-free (PFWD) and maximal walking distance (MWD) were measured. Single alprostadil infusion induced an improvement in WBV, WBF, and oxygen transport, and an increase in adenosine plasma levels. Long-term alprostadil administration produced a decrease in WBV only, without significant changes in WBF, Htc, fibrinogen, P50, 2,3-diphosphoglycerate, also inducing a significant prolongation of PFWD and MWD. The possibility is suggested that pulse rises in adenosine plasma levels play a role in the effects of chronic alprostadil administration, maybe in a way similar to that observed in the phenomenon of ischaemic preconditioning,

Experimental model of short-time exercise-induced preconditioning in POAD patients.

Regular physical exercise improves walking performance in patients affected with peripheral obliterative arterial disease (POAD). The mechanisms underlying the phenomenon are still controversial. In order to verify the hypothesis that physical conditioning of lower limbs on a treadmill and ischemic preconditioning of the heart could share some biological aspects, 14 POAD subjects underwent a training program on the treadmill consisting of five repeated submaximal exercises at five-minute and two-hour intervals preceding the maximal tolerance test. Moreover, a protocol with two daily submaximal walking exercises over one week was also performed. Pain-free and total walking distance were measured before and after they performed the program. Moreover, plasma levels of adenosine and adenosine triphosphate (ATP) were measured and polymorphonuclear (PMN) leukocyte activity was studied together with rheologic parameters. Pain-free distance was prolonged by 15.4% and 14.3%, and total distance was prolonged by 23.1% and 26.9%, in the exercises with five-minute and two-hour intervals, respectively. After one week of daily exercises, the onset of pain and the end of the test were delayed by 24% and 43.7%, respectively. An improvement in blood rheology and a reduced PMN reactivity were also observed with the three protocols, associated with an increase in plasma levels of adenosine and ATP. Similarly to ischemic preconditioning in the heart, the possibility is suggested that an adenosine-mediated mechanism may contribute to the development of physical conditioning in treadmill-trained POAD patients.

Pharmacological preconditioning of ischaemia.

Five repeated submaximal treadmill exercises at 2 h intervals following a maximal test prolong walking distance and reduce haemorheological derangement in a second maximal test in patients affected with peripheral obliterative arterial disease (POAD). An increase in adenosine plasma levels is observed during maximal tests, thus suggesting the possibility of an ischaemic preconditioning of lower limbs. The intravenous infusion of 50-100-200 mg buflomedil, and the oral administration of 300-600-900 mg of the drug in POAD patients, also produce an increase in plasma levels of adenosine. Finally, 600 mg buflomedil orally at 12 h intervals produced pulse increase in adenosine plasma levels without any accumulation of the drug or adenosine for at least one week. The possibility of a pharmacological preconditioning of ischaemia is suggested.

Pharmacodynamic Effects of Sulodexide on Profibrinolytic and Haemorrheological Patterns.

Twenty-four patients with vascular disorders, randomly divided into 3 dosage groups of 8 patients, were treated with a single oral dose of sulodexide (50, 100 or 200mg) and placebo. Tissue plasminogen activator (t-PA), plasminogen activator inhibitor (PAI-1) activity and antigen, euglobulin lysis time, α2-antiplasmin, plasminogen, fibrinogen, blood and plasma viscosity, and whole blood filtration rate were determined before administration and over the following 24 hours. Sulodexide significantly increased t-PA activity linearly with the dose over the range of 50 to 200mg. At the same time, it also significantly decreased the concentration of PAI-1 linearly and proportionally with the dose. No clear effects were observed on the other monitored parameters, although euglobulin lysis time and plasma viscosity showed a tendency to decrease after the administration of sulodexide. These results justify the clinical activity of sulodexide. Indeed, the concomitant increase of t-PA and decrease of PAI-1 activity and antigen might increase the natural fibrinolytic activity with a physiological potentiation, without other adverse effects. The known activity of sulodexide in decreasing plasma viscosity during long term treatment is, however, not immediately explicable by the single-dose effects.

[The effects of vinburnine on the blood rheology parameters and on the oxyhemoglobin dissociation curve and 2,3-diphosphoglycerate. In vitro research]. / Effetti della vinburnina sui parametri emoreologici e sulla curva di dissociazione ossiemoglobinica e 2-3 difosfoglicerato. Ricerche in vitro.

The authors investigate the protective action of vinburnine on impairment of blood haemorheology and on metabolic parameters due to in vitro ageing of blood samples. In each sample the following parameters were measured: blood viscosity and filterability, p50 and 2,3-DPG. Vinburnine is able to induce a slight improvement of haemorheological parameters and of p50 compared to controls. After incubation for 4 hr, a reduced impairment of the mentioned parameters was observed in comparison with controls. Some hypotheses are discussed about the mechanisms of action of the drug.

[The effects of the acute administration of vinburnine on blood rheology, oxygen transport and regional circulation under normal conditions and in hypoxemia. In vivo research]. / Effetti della somministrazione acuta di vinburnina sulla reologia ematica, trasporto dell'ossigeno e sulla circolazione distrettuale in condizioni normali e di ipossiemia. Richerche in vivo.

Vinburnine has been shown to be effective in avoiding chronic ischaemic tissue injury. Many studies have demonstrated the antihypoxic and oxygenation properties of this drug. In our study we have evaluated in two groups of patients the effects on blood rheology, oxygen transport, regional circulation and ergospirometric data of 40 mg vinburnine infused in a systemic vein. We have selected in the first group 10 patients with low hemoglobin oxygen affinity (p50 28.6 +/- 1.37 mmHg), in the second one 7 patients with normal values (p50 26.6 +/- 0.84 mmHg). In the two groups of the study we evaluated nutritional blood flow by a plethysmographic method, blood gas analysis [correction of hemogasanalitic] parameters in arterial and venous blood, haemoglobin oxygen affinity expressed as p50 and erythrocytic 2,3-DPG, hemorheologic and ergospirometric parameters. Data were evaluated in basal conditions and at the end of the infusion. The improvement of rheological properties, hemodynamic and metabolic data in the two groups of the study seems to confirm the oxyphoretic properties of this drug.

[Calcium dobesilate, hemorheology, fibrinolysis and endothelium. New perspectives on the prevention of diabetic microangiopathy. Clinical pharmacological study]. / Dobesilato di calcio, emoreologia, fibrinolisi ed endotelio. Nuove prospettive nella prevenzione della microangiopatia diabetica. Studio di farmacologia clinica.

The authors report the results of a double-blind cross-over study on calcium dobesilate in which two groups of eight recent-onset type-II diabetics were treated either p.o. (1 g once daily) or i.v. (500 mg in 100 ml of physiological saline) with calcium dobesilate or with placebo. During oral administration of the drug, blood rheology and total fibrinolytic capacity were assessed by calculating euglobulin lysis time. In view of the evidence for a viscosity-lowering action of the drug (which had already been found in "long-term" studies) and of potentiation of fibrinolytic activity, intravenous treatment was started with the object of elucidating the possible mechanisms of action, evaluating at the same time other parameters concerning the functional fibrinolytic pathways. It has thus been possible to ascertain that the drug has "rheologic" activity, interferes with the function of endothelial cells by stimulating the release of tissue plasminogen activator and thus increases fibrinolytic activity while not interfering with the clotting function and not altering platelet beta-thromboglobulin secretion. These findings appear to confirm the possibilities for therapeutic use of calcium dobesilate which is thought to act on a variety of pathogenetic mechanisms involved in diabetic microangiopathy.

Allopurinol prevents ischaemia-dependent haemorheological changes.

Pre-treatment with allopurinol is able markedly to attenuate the deterioration in blood viscosity (BV) and whole blood filterability (WBF) that occurs after ischaemia during exercise. It also reduces the exercise-induced increase in serum oxidase activity, although this action is slightly less effective in peripheral obliterative arterial disease (POAD) patients. Conversely, allopurinol is completely ineffective in modifying haemorheological parameters in vitro, and it does not affect superoxide anion generation or enzyme release from neutrophils stimulated in vitro with formyl-methionyl-leucyl-phenylalanine (FMLP). It is suggested that allopurinol may attenuate changes in BV and WBF by affecting xanthine-oxidase-dependent free radical formation in tissues.

Hemorheological factors in the pathophysiology of acute and chronic cerebrovascular disease.

The hemorheologic changes in three groups of patients suffering from acute and chronic cerebrovascular diseases were studied. Firstly, a horizontal study on 57 patients with definite stroke and on 49 patients with TIA was made. Plasma viscosity, whole blood filtration rate, fibrinogen concentration and hematocrit were evaluated as markers of the rheological property of blood. Blood samples were drawn within 6 h from the onset of vascular syndrome. The findings were compared with values obtained in 112 as controls. At the same time, washed red cell filtration rate, together with lactoferrin, betaglucuronidase and beta-thromboglobulin plasma level were assayed. In both groups the onset of the vascular storm was associated with a marked increase of plasma fibrinogen and of blood and plasma viscosity and a significant decrease of whole blood filterability. Lactoferrin, betaglucuronidase and beta-thromboglobulin levels were also significantly increased. Following this, a longitudinal study was performed on 27 patients with definite stroke and 32 patients with TIA. The clinical regression of acute stroke was associated with the progressive reduction of rheological abnormalities. Finally, 81 patients with clinical diagnosis of cerebrovascular disease due to previous stroke or repeated TIA were studied together. An increase of blood viscosity, of fibrinogen concentration and of hematocrit and a decrease of blood filtration rate together with higher levels of beta-thromboglobulin were registered. These results confirm the existence of an association between CVD and hemorheological alterations and suggest more in depth research directed towards identifying the significance of these alterations in the pathogenesis of tissue ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

[A syllectrometric method to study erythrocyte aggregation]. / Considerazioni su una metodica sillectometrica per lo studio dell'aggregabilità eritrocitaria.

The authors show a new method to study erythrocyte aggregation; the results of in vitro study, obtained by modification of several parameters (hematocrit, immunoglobulins, fibrinogen concentrations), are exposed. The authors did not find in vivo correlations between MAE and hemorheological parameters in different diseases; they found low MAE values only in myelomatous subjects. Adding erythrocytes from healthy donors to myelomatous plasma and vice versa, they found low MAE values only in samples containing erythrocytes and plasma from myeloma. These results suggest that many factors, not only erythrocyte aggregability, contribute to determine MAE (Mean Aggregation Entity).

[Assay of erythrocyte ATP by chemoluminescence. Protective action induced by pentoxifylline on the depletion of energy from stored erythrocytes]. / Valutazione dell'ATP eritrocitario per chemiluminescenza. Azione protettiva indotta dalla pentossifillina sulla deplezione energetica da conservazione delle emazie.

A new method to measure erythrocyte ATP levels is used. The authors have incubated 6 whole blood samples and 7 samples containing washed red blood cells for 6 h. They measured ATP levels and confirmed an important decrease of the values during the time. If the same samples were incubated with pentoxifylline (1.4 X 10(-4) M), the ATP decrease was less relevant.

[The relation between erythrocyte filterability and platelet aggregation (in vitro studies in normal subjects and those with vascular disease before and after isotonic exercise)]. / Studio di alcuni aspetti dei rapporti fra filtrabilità eritrocitaria ed aggregazione piastrinica (ricerche in vitro in soggetti normali e vasculopatici prima e dopo sforzo isotonico).

The aim of this study was to evaluate the possible action in vitro of the platelets on the rheological behavior of red blood cells in healthy subjects and in patients with peripheral obliterative arterial disease before and after an isotonic exercise. Red blood cells and platelets from control subjects and from patients were tested in several ratios before and after the exercise studying the erythrocyte filterability. beta-thromboglobulin, a platelet-specific protein, was determined in vivo in all subjects before and after the exercise and in vitro as percent of increase between PPP and PRP activated, to monitor the platelet release. The results showed the interrelationship between platelet activation and rheological behavior of red blood cells.

[Hemorrheological changes in ischemic heart disease]. / Le alterazioni emoreologiche della cardiopatia ischemica.

Ischemic cardiopathy in its various clinical manifestations, whether acute (angina pectoris or myocardial infarction) or chronic (chronic coronary insufficiency), has shown in recent years particular hemorheological characteristics of its own. The observation of patients with such diseases has allowed us to record the existence of modifications in the parameters indicative of rheological damage. Numerous studies have been made, many of which are still in progress, with the aim of clarifying the relationships between these data and the disease. In our experience an increase in blood and plasma viscosity and a decrease in red cell deformability are often present in a manner which is statistically significant, if these patients are compared with normal subjects. Hemorheological change is more evident in the acute forms of myocardial ischemia. In fact, in angina pectoris the occurrence of pain is always accompanied by an increase in blood viscosity and by a worsening of red cell deformability both during spontaneous crises and during provocative tests. The hemorheological damage tends to diminish fairly rapidly when the crisis is over, even if the level of stabilization proves to be still higher than normal. In myocardial infarction higher levels of viscosity appear for a brief period after the onset with a slight tendency to diminish up until the 30th day. With the aim of ascertaining whether the alteration is more evident precisely at the point where the ischemia occurs, we chose a necessarily limited number of subjects, undergoing coronarography and atrial pacing for diagnostic purposes, and decided to control the hemorheological data not only in the systemic venous blood but also in the blood taken from the coronary sinus. Our data has shown that the level of viscosity and of red cell filtrability, in the blood taken from the coronary sinus, is worse than those of the systemic venous blood and that, after atrial pacing, in negative pacing subjects the variations are of slight significance whilst in positive pacing subjects we observe a rapid increase in viscosity and a decrease in red cell filtrability. This seems to confirm what we have already observed in the limbs affected by peripheral ischemia, and to demonstrate the existence of a local hyperviscosity syndrome which, even in the myocardium, appears to be dependent on the tissue ischemia.

[Methodological survey of whole blood filtration in the evaluation of erythrocyte deformability. I. Effect of temperature]. / Rilievi metodologici sulla filtrazione del sangue intero nella valutazione della deformabilità eritrocitaria. I. Effetto della temperatura.

We have demonstrated how temperature affects whole blood filterability. The filtration index appears to be dependent on temperature; the higher temperature is, the higher it rises. At body temperature of 37 degrees C the method resulted more reliable.

[Methodological survey of whole blood filtration in the evaluation of erythrocyte deformability. II. Effect of preservation time at various temperatures]. / Rilievi metodologici sulla filtrazione del sangue intero nella valutazione della deformabilità eritrocitaria. II. Effetto del tempo di conservazione a varie temperature.

We have demonstrated how conservation time affects whole blood filterability. The filtration index decay appears just after withdrawal and is present, with different characteristics, both at room temperature and at 37 or 4 degrees C. It is absolutely necessary to take measurements immediately after blood withdrawal.

[Methodological survey of whole blood filtration in the evaluation of erythrocyte deformability. III. Relative influence of various cellular components]. / Rilievi metodologici sulla filtrazione del sangue intero nella valutazione delle deformabilità eritrocitaria. III. Influenza relativa della diverse componenti cellulari.

We have counted the different types of blood cells before and immediately after filtration. During filtration, an almost equal quantity of each type of cells remained in the filter, with a slightly higher percentage of leucocytes. The problem regarding occlusion of filter pores should be considered in the light of these findings.

[Can normovolemic hemodilution really modify blood flow in the limbs?]. / L'emodiluizione normovolemica può realmente modificare il flusso ematico degli arti?

A clinical study on the effects of the normovolemic hemodilution on hemorheological and peripheral hemodynamic parameters has been carried out in patients with peripheral obliterative arterial disease. Two sessions have been performed: the acute test consisted in daily normovolemic hemodilutions for a period of 7 days in 10 patients with the determination of hemorheological and peripheral hemodynamic parameters before and after each treatment. A chronic study was then carried out in 8 patients by applying weekly normovolemic hemodilutions, by evaluating the hemorheological parameters as in the first session and by measuring the peripheral hemodynamic parameters at the beginning, after 5 weeks and at the end of the treatment. The results are reported and the possible mechanism of action of normovolemic hemodilution is discussed.