CHF-1024, a DA2/alpha2 agonist, blunts norepinephrine excretion and cardiac fibrosis in pressure overload

We compared the effects of an ACE inhibitor, captopril, with those of a DA2-dopaminergic/alpha2-adrenergic receptor agonist (CHF-1024) on neuroendocrine activation and cardiac fibrosis in a model of pressure-overload hypertrophy. Interrenal aortic stenosis was performed in 89 rats, treated with CHF-1024 (0.33, 2 or 6 mg kg(-1) day(-1)), or captopril (1 g/L). Hemodynamic variables were recorded. Cardiac and renal weights, plasma aldosterone, renin activity and urinary catecholamine excretion were measured, as well as cardiac collagen. Blood pressure was lower in stenotic animals treated with CHF-1024 compared to vehicle (161 +/- 10 vs 219 +/- 10 mmHg, p < 0.01), but LV weight was similar. CHF-1024 elicited a marked dose-dependent attenuation of urinary norepinephrine excretion (1.80 +/- 0.18 in controls compared to 0.40 +/- 0.14 microg/24 h at the highest dose, p < 0.01) and of LV perivascular fibrosis. Captopril provoked a marked hypotension, reduced cardiac and body weights, plasma aldosterone concentration, dopamine excretion and perivascular collagen. The DA2/alpha2 agonist CHF-1024 effectively blunts adrenergic drive and cardiac fibrosis in a rat model of pressure overload.

Effects of a DA2/alpha2 agonist and a beta1-blocker in combination with an ACE inhibitor on adrenergic activity and left ventricular remodeling in an experimental model of left ventricular dysfunction after coronary artery occlusion

Renin-angiotensin-aldosterone and sympathetic nervous systems overactivity play a major role in worsening the extent of heart failure. Attenuation of neurohumoral activation with angiotensin-converting enzyme (ACE) inhibitors and beta-blockers has proven beneficial in congestive heart failure. Because ACE inhibition is a recommended treatment for heart failure, this study was designed to test the effects on neurohumoral activation, hemodynamics, and left ventricular (LV) volume of the combination of an ACE inhibitor (delapril) with a DA2-dopaminergic receptor/alpha2-adrenoceptor agonist (CHF-1024) or a beta1-adrenoceptor antagonist (metoprolol) after a moderate to large myocardial infarction (MI) in rats. MI was induced by left coronary artery ligation in 134 rats, and six were not operated on. After 2 months, the animals with ECG evidence of MI were treated for 1 more month with CHF- 1024, 0.33 mg/kg/day or with metoprolol (10 mg/kg/day), delivered through implanted osmotic minipumps, in addition to delapril (6 mg/kg/day) in the drinking water. Daily urinary excretion of norepinephrine (NE) and circulating concentration were measured. Hemodynamic variables were measured, and three-dimensional morphometric analysis was done on the diastole-arrested hearts to quantify infarct size and LV geometry. In conscious animals, delapril alone or with CHF-1024 or metropolol did not modify heart rate or systolic blood pressure. Both combination treatments, however, significantly reduced heart rate in anesthetized animals compared with the group receiving vehicle. Infarct size was not different between treatments, averaging 20-22% of LV volume. The threefold increase of LV chamber volume in infarcted rats was significantly attenuated by delapril alone or with CHF-1024 or metoprolol (-37 to -44%, p<0.05). Treatment with a combination of the ACEi and CHF-1024 tended to normalize the shape of the LV cavity. Urinary NE excretion was unaffected by delapril alone but was reduced by the addition of CHF-1024 or metoprolol. In conclusion, 1 month of treatment with doses of delapril having no hemodynamic effect, reduced LV volume in a model of chronic heart failure. When CHF-1024 or metoprolol was given with delapril, sympathetic activation decreased with no unwanted effects, such as excessive hypotension.

Protective effects of delapril, indapamide and their combination on stroke occurrence and lifespan in salt-loaded stroke-prone spontaneously hypertensive rats

The effects of long-term oral administration of delapril (CAS 83435-67-0), indapamide (CAS 26807-65-8) and their combination on the occurrence of stroke and on mortality were investigated in young salt-loaded stroke-prone spontaneously hypertensive rats (SHRsp) for 31 weeks of treatment (8th-39th week of age) and up to 8 weeks thereafter. Body weight and saline consumption were investigated at regular intervals and cerebrovascular lesions, renal and heart weight were assessed after sacrifice. Untreated SHRsp served as controls. About 50% of control animals died within 6 weeks of saline administration and in 56% of surviving animals cerebral lesions were present at sacrifice, while no death and no cerebral lesions were observed in animals drinking saline, to which delapril, indapamide and their combination had been added, up to the end of treatment. This protective effect was maintained even in the withdrawal period. All treatments induced a highly significant (p < 0.001) reduction of heart weight/body weight and kidney weight/body weight ratios.

Comparative efficacy of a DA2/alpha2 agonist and a beta-blocker in reducing adrenergic drive and cardiac fibrosis in an experimental model of left ventricular dysfunction after coronary artery occlusion

Attenuation of neuroendocrine activation may be beneficial in congestive heart failure. Sympathetic nervous system overactivity can be reduced by receptors blockade or by reducing norepinephrine (NE) spillover. This study evaluated and compared the effects of a DA2-dopaminergic receptor/alpha2-adrenoceptor agonist (CHF-1024) and a beta1-adrenoreceptor antagonist in terms of hemodynamics, ventricular remodeling, beta-adrenergic drive, and cardiac fibrosis after myocardial infarction (MI) in rats. MI was induced by left coronary artery ligation in 213 rats, whereas 12 were left unoperated on. After 2 months, the operated-on animals were treated for 1 more month with CHF-1024 at either 0.33 mg/kg/day (low dose) or 1 mg/kg/day (high dose) or with metoprolol (10 mg/kg/day), delivered through implanted osmotic minipumps. Plasma concentration and urinary excretion of NE were measured before the rats were killed. Hemodynamic variables were measured and morphometric analysis was done on the diastole-arrested hearts to quantify left ventricular remodeling and interstitial collagen density. Metoprolol treatment tended to normalize LV end-diastolic pressure (LVEDP). CHF-1024 at either dose, and metoprolol, significantly reduced collagen deposition in LV of infarcted animals (from 8.8 +/- 0.5% LV area in vehicle-treated rats to 6.6 +/- 0.2% or 6.4 +/- 0.2% after the low or high dose of CHF-1024, respectively; p < 0.05). Similarly, CHF-1024 at either dose reduced the plasma concentration of NE (from 224 +/- 53 pg/ml to 60 +/- 7 pg/ml or 87 +/- 13 pg/ml; p < 0.05) and urinary excretion of NE in rats with MI, whereas beta-blockade did not affect these variables. In conclusion, CHF-1024 infused for 1 month to rats with LV dysfunction reduced heart rate, NE spillover, and collagen deposition, without unwanted effects, only appearing at the higher dose. Effective beta-blockade with metoprotol reduced LVEDP with no effects on heart function. Neither DA2/alpha2 stimulation nor beta-blockade altered LV remodeling after coronary artery ligation.

Evaluation of potentially injurious effects of exogenous surfactant lysophospholipids on the alveolar epithelium and pulmonary mechanics

Although lysophospholipids are normally found in the lung and their presence is connected to the metabolic pathway of surfactant phospholipids, several studies have reported that their intratracheal instillation is able to induce severe alveolar epithelial injury. Since lysophospholipids are normally present in exogenous surfactants as a consequence of the nonenzymatic hydrolysis of parent phospholipids during their production and shelf-life, the aim of this study was to test the potential toxicity of surfactant lysophospholipids in artificially ventilated newborn rabbits in comparison with that of pure lysophosphatidylcholine (Lyso-PC) suspensions. In premature (surfactant-deficient) animals, a commercially available Curosurf batch (0.56 mg Lyso-PC/ml) improved lung-thorax compliance and reduced lactate dehydrogenase (LDH), total protein and hemoglobin contents in bronchoalveolar lavage (BAL) fluid. The same batch submitted to thermal stress in order to increase the Lyso-PC content (10.2 mg Lyso-PC/ml) failed to improve lung mechanics but did not induce any significant change in biochemical markers in BAL fluid. When suspended in saline, pure Lyso-PC had a dramatic and dose-dependent tissue-damaging effect with increased LDH, hemoglobin and protein contents in BAL and a fall in the lungthorax compliance, in both immature and mature (near-term) animals. The lack of toxicity of Lyso-PC in Curosurf might be explained by an interaction with surfactant phospholipids.

Ipriflavone does not alter bone apatite crystal structure in adult male rats

We have previously found that a short-term treatment with high doses of ipriflavone increased bone density and improved the biomechanical properties of adult male rat bones, without altering their mineral composition. To determine whether this effect can be associated with alterations of bone crystal structure, we have performed X-ray diffraction analysis of bones obtained from rats treated with ipriflavone at doses that were effective in inducing favorable changes on bone density and biomechanics. Eighteen-week-old male Sprague Dawley rats were treated by oral route with either ipriflavone (200 or 400 mg/kg/day), or its vehicle for 12 weeks. The treatment was well tolerated and body weight increased to the same extent in all animals. As a measure of bone crystallinity, we examined the (310) and (002) reflections of the X-ray diffraction patterns, corresponding to the directions perpendicular and parallel to the c-axis of the crystals, respectively. No major differences were observed between ipriflavone-treated and control animals for the broadening parameter beta(1/2) for (310) and (002) peaks, as well as for lattice parameters. Therefore, a 12-week treatment with ipriflavone at high doses does not induce significant modifications of bone "crystallinity." Thus, the positive effect of ipriflavone on bone mineral density appears to be associated with an increased apatite crystal formation rather than an increase of crystal size. These results provide further evidence for the safety and usefulness of ipriflavone in the treatment of osteoporotic syndromes.

Inhibition of parathyroid hormone-stimulated resorption in cultured fetal rat long bones by the main metabolites of ipriflavone

Ipriflavone is an isoflavone derivative used in the prevention and treatment of postmenopausal and senile osteoporosis in humans. To assess the potential contribution of the main in vivo ipriflavone metabolites (M1, M2, M3, and M5) on the pharmacological properties of the drug, we investigated their effect on osteoclastic resorption induced by the well-known stimulator of bone resorption bovine parathyroid hormone fragment 1-34 (bPTH 1-34). The study was carried out using fetal rat long bones in stationary cultures. The amount of osteoclastic resorption was determined by assaying for 5 days the release from bones in the media of previously incorporated 45Ca. All metabolites were effective at inhibiting osteoclastic resorption. Maximal potency was shown by M3, characterized by a significant effect at 10 microM (P < 0.01) and by an IC50 value of 17 microM. M2 was about threefold less potent than M3 (IC50 = 46 microM). M1 and M5 were the least active compounds with an IC50 value of 117 and 200 microM, respectively. The present evidence indicates that metabolites of ipriflavone, in particular M3 and M2, inhibit bPTH 1-34-induced bone resorption in fetal rat long bones. Accordingly, they may play an important role in the pharmacological effects of the drug.

The involvement of the release of nitric oxide in the pharmacological activity of the new furoxan derivative CHF 2363

1. The mechanism of action and the pharmacological effects of the new furoxan derivative, CHF 2363 (4-ethoxy-3-phenylsulphonylfuroxan), were investigated. 2. Pre-incubation of CHF 2363 with human platelet-rich plasma produced a concentration-dependent inhibition of the platelet aggregation induced by collagen, adenosine diphosphate (ADP) and platelet activating factor (PAF). The test compound was about 5 times more potent than sodium nitroprusside. 3-Isobutyl-1-methyl-xanthine (IBMX) potentiated the antiaggregating effect of CHF 2363. 3. CHF 2363 was a potent inhibitor of rubbed endothelium rabbit aortic ring contraction induced by noradrenaline. Comparison of IC50 values showed that CHF 2363 was as potent as glyceryl trinitrate (GTN). 4. Increasing concentrations of CHF 2363 elevated platelet guanosine 3':5'-cyclic monophosphate (cyclic GMP) levels. Adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels were unaffected. 5. Oxyhaemoglobin reduced all the pharmacological actions of the test compound. Moreover, CHF 2363 concentration-dependently released nitric oxide (NO) in platelet-rich plasma. The NO release was correlated to its ability to increase platelet cyclic GMP levels. 6. After exposure of rat aortic strips to supramaximal concentrations of GTN (550 microM), the vasorelaxant activity of CHF 2363 did not change, although that of GTN decreased about 55 fold. 7. It has been concluded that the new furoxan derivative CHF 2363 exerts a potent antiaggregating and vasorelaxant activity via NO release and increase of cyclic GMP levels. No in vitro cross tolerance between GTN and CHF 2363 was observed.

Effect of long-term treatment with L-deprenyl on the age-dependent microanatomical changes in the rat hippocampus

Chronic treatment with L-deprenyl increases both mean and maximum life span and improves cognitive functions in the aged rat. The present study was designed to evaluate whether long-term treatment with L-deprenyl at a dosage not inhibiting the monoamine oxidase-B (MAO-B) (1.25 mg/kg/day) or inhibiting the enzyme activity (5 mg/kg/day) had any effect on the age-dependent microanatomical changes in the rat hippocampus. The hippocampus was chosen in view of its key role in learning and memory functions. Treatment with L-deprenyl started at 19 months and lasted until the 24th month of age. Age-matched untreated rats were used as a control, whereas 11-month-old rats were used as an adult reference group. The number of nerve cell and glial fibrillary acidic protein-immunoreactive astrocyte profiles in the CA1 and CA3 fields of the hippocampus and in the dentate gyrus was decreased and increased, respectively in aged compared with adult rats. Treatment with 5 mg/kg/day, but not with 1.25 mg/kg/day L-deprenyl increased the number of neuronal profiles and decreased the number of astrocytes in the hippocampus of aged rats. The density of zinc stores in the associative intrahippocampal pathway of mossy fibres, which was decreased in aged animals, was increased after treatment with the two doses of L-deprenyl. Lipofuscin accumulation within the cytoplasm of pyramidal neurons of the hippocampus was reduced dose dependently by L-deprenyl treatment. These results suggest that long-term treatment with L-deprenyl is able to counter the expression of age-dependent microanatomical changes in the rat hippocampus. These effects seem only partially correlated with the MAO-B inhibitory activity of L-deprenyl.

Influence of treatment with L-deprenyl on the structure of the cerebellar cortex of aged rats

Treatment with L-deprenyl increases mean and maximum life span in the rat and reverses memory and learning deficits associated with old age. Since only sparse information is available concerning the influence of L-deprenyl administration on the aging brain microanatomy, we have investigated the effect of long-term treatment with L-deprenyl on the structure of the cerebellar cortex in the aged rat. The cerebellar cortex was used since it represents a useful model for assessing age-related changes in nervous system anatomy and function. Male Sprague-Dawley rats were treated from the 19th to the 24th month of age with a daily oral dose of 1.25 mg/kg or 5 mg/kg L-deprenyl. Age-matched rats were left untreated and used as a control group. Eleven-month-old untreated rats were used as an adult reference group. The density of Purkinje and granule neuron profiles as well as the intensity of Nissl's staining within the cytoplasm of Purkinje neurons were reduced in 24-month in comparison with 11-month rats. Moreover, an increased accumulation of lipofuscin was noticeable in the cytoplasm of Purkinje neurons of old rats as well as an increase in MAO-B activity in the molecular layer of the cerebellar cortex. The two doses of L-deprenyl increased the density of both Purkinje and granule neuron profiles and the intensity of Nissl's staining in the cytoplasm of Purkinje neurons and reduced lipofuscin deposition within Purkinje neurons. The lower dose of L-deprenyl caused only a slight decrease in MAO-B activity, whereas the 5-mg/kg/day dose remarkably reduced it. These results suggest that long-term treatment with L-deprenyl counters the expression of some age-related microanatomical changes in the rat cerebellar cortex. The possible independence of the effects of the compound on age-related microanatomical changes of the cerebellar cortex and on MAO-B inhibitory activity is discussed.

Neuroanatomy of aging brain. Influence of treatment with L-deprenyl

The present study was designed to assess the influence of long term L-deprenyl treatment on some microanatomical parameters of aging rat frontal cortex and hippocampus. Male Sprague-Dawley rats of 19 months of age were divided into three groups. Rats of the first group received an oral daily dose of 1.25 mg/kg L-deprenyl; animals of the second group were treated with an oral daily dose of 5 mg/kg L-deprenyl, whereas rats of the third group were left untreated and used as control. Treatment lasted for 5 months, and rats were sacrificed at 24 months. At this age they were considered to be old. Another group of 11-month-old rats was used as an adult reference group. The density of nerve cell profiles and of glial fibrillary acidic protein (GFAP) immunoreactive astrocytes was decreased and increased respectively in the frontal cortex and in the different portions of the hippocampus in old in comparison with adult rats. A decrease in the intensity of sulfide silver staining in the mossy fibers of the hippocampus was also observed in old rats. Moreover, a cytoplasmatic accumulation of lipofuscin was noticeable in old rats as well as a significant increase of the monoamine-oxidase (MAO) B reactivity both in the frontal cortex and in the hippocampus. A higher density of nerve cell profiles, of sulfide silver staining, and fewer astrocyte profiles were noticeable in the frontal cortex and in the hippocampus of old rats treated with 5 mg/kg/day of L-deprenyl. This dose of the compound also significantly reduced lipofuscin accumulation and MAO-B reactivity in old rats. However, the lower dose of the compound did not cause any statistically significant effect on the microanatomical parameters investigated with the exception of sulfide silver staining and lipofuscin accumulation, which were increased and decreased respectively after 1.25 mg/kg per day of L-deprenyl. The above results suggest that long-term treatment with L-deprenyl is able to counter some microanatomical changes typical of the aging frontal cortex and hippocampus in the rat. These changes seem to be in part related to the MAO-B inhibitory activity of L-deprenyl.

CHF 2206, a new potent vasodilating and antiaggregating drug as potential nitric oxide donor

The effects of the new 3,4-disubstituted furoxan, CHF 2206, on vascular tone, platelet aggregation and platelet cyclic 3',5'-guanosine monophosphate (cGMP) levels were investigated. The compound was a potent inhibitor of rabbit aortic ring contraction induced by norepinephrine, the stable prostaglandin F2 alpha analogue, U-46619, and KCl; this activity was independent of endothelium integrity. When pre-incubated with platelet-rich plasma, CHF 2206 potently reduced in a dose-dependent manner the aggregation induced by the threshold aggregating concentration of collagen, ADP or platelet activating factor (PAF). In the same experimental conditions, the test compound increased the platelet cGMP levels and this rise was clearly associated with the inhibition of platelet aggregation. Moreover, 3-isobutyl-1-methyl-xanthine (IBMX) 5 microM potentiated the antiaggregating activity of CHF 2206. These results indicate that the increase in cGMP plays a key role in the CHF 2206-elicited responses. Oxyhemoglobin reduced all the pharmacological actions of the test compound. This evidence, along with the capacity of CHF 2206 to cause inorganic nitrite production in the presence of platelet-rich plasma, strongly suggests that nitric oxide (NO) may be a common reactive intermediate responsible for the effects induced by the drug. In conclusion, the furoxan derivative CHF 2206 exerts a potent antiaggregating and vasodilating activity with a pharmacological profile similar to the one described for NO-donating pro-drugs.

Influence of long-term treatment with L-deprenyl on the age-dependent changes in rat brain microanatomy

The present study was designed to assess whether treatment with the monoamine oxidase-B (MAO-B) inhibitor L-deprenyl, which has been documented to increase both mean and maximum survival in aged rats as well as sexual performance and cognitive function, has any effect on the age-related microanatomical changes occurring in the rat brain. Male Sprague-Dawley rats received a subcutaneous injection of 0.25 mg/kg L-deprenyl every other day from the 19th to the 24th month of age. Age-matched control rats were injected with saline, whereas 11-month-old untreated rats were used as an adult reference group. Both body and brain weight were increased as a function of age, and they were unaffected by treatment with L-deprenyl. The density of nerve cell profiles in the frontal cortex, in the CA-1 and CA-3 subfields of the hippocampus, in the dentate gyrus and in the cerebellar cortex were decreased in aged rats in comparison with adult rats. The density of nerve cell profiles in the above brain areas of L-deprenyl-treated rats was not significantly higher in comparison with age-matched control animals with the exception of Purkinje neuron profiles. The intensity of Nissl's staining, which may be related to the protein synthetic capabilities of nerve cells, is reduced within pyramidal neurons of the hippocampus and Purkinje neurons of the cerebellar cortex of aged rats. The intensity of Nissl's staining in L-deprenyl-treated rats was not different from adult rats. Lipofuscin deposition was significantly increased within the cytoplasm of pyramidal neurons of the frontal cortex, of the CA-3 subfield of the hippocampus and of Purkinje neurons of the cerebellar cortex. L-Deprenyl administration decreased lipofuscin accumulation within the cytoplasm of the above mentioned nerve cell types. The density of sulphide-silver staining in the intrahippocampal pathway of mossy fibres, which participate in the elaboration of passive avoidance responses, is decreased in aged rats. Treatment with L-deprenyl counters this age-related reduction. The above results suggest that long-term treatment with L-deprenyl is able to counter the expression of some microanatomical changes typical of aging brain.

Repeated administrations of (-)-deprenyl increase [3H]MK801 binding in rat brain and antagonize the impairment of passive avoidance conditioning induced by N-methyl-D-aspartate receptor antagonists

Repeated but not single administrations of the MAO type B inhibitor (-)-deprenyl (1 mumol/kg s.c. for 21 consecutive days) antagonized the impairment of passive avoidance retention induced by the N-methyl-D-aspartate (NMDA) receptor antagonists 2-amino-5-phosphonovalerate (APV), ketamine and dizocilpine (MK801), in rats. In well-washed membranes prepared from the hippocampi of rats repeatedly treated with (-)-deprenyl, the [3H]MK801 specific binding was increased. In contrast, repeated MAO B-selective doses of pargyline or (+)-amphetamine, as well as single injections with (-)-deprenyl failed to change [3H]MK801 binding. It is suggested that the effects of repeated (-)-deprenyl administrations upon NMDA receptors and upon the impairment of acquisition of a passive avoidance task induced by NMDA antagonists could be independent of MAO inhibition.

Lung gas volumes and expiratory time constant in immature newborn rabbits treated with natural or synthetic surfactant or detergents

Immature newborn rabbits delivered at a gestational age of 27 days were tracheotomized and treated, via the tracheal cannula, with clinically recommended doses of natural or synthetic surfactant (Curosurf and Exosurf, respectively). Littermates received 0.1% tyloxapol, 5% Tween 20, or saline. The dose volume of Curosurf was 2.5 ml/kg, that of the other materials 5 ml/kg. Animals were kept in a multiplethysmograph system and ventilated for 30 min with a standardized sequence of insufflation pressures. End-expiratory lung gas volume was calculated at the end of the experiment from measurements of lung weight and total lung volume. Tidal volumes were significantly improved in all groups of animals receiving surfactant or detergents. However, expiratory time constant (determined from the tidal volume tracing) was significantly longer, and end-expiratory gas volume significantly larger, in animals treated with Curosurf than in those receiving Exosurf or detergents. These differences were confirmed by semiquantitative evaluation of alveolar air expansion in histological sections. In addition, airway epithelial necrosis was reduced in animals receiving Curosurf, Exosurf, or Tween 20, but not in animals treated with tyloxapol. The discrepancy between improvements in tidal volume, expiratory time constant, and end-expiratory gas volume reflects failure of lung stabilization in animals treated with Exosurf or detergents, probably due to absence of specific hydrophobic proteins in the synthetic products.

No-mimetic furoxans: arylsulphonylfuroxans and related compounds

A new class of methylfuroxans and methylfurazans arylthio, arylsulphinyl and arylsulphonyl substituted, characterized by vasodilating and antiaggregatory properties, is described. Vasodilating activity, tested on rabbit aortic rings percontracted with 1 microM noradrenaline, is enhanced by N-oxidation of the furazan ring and is maximized by increase of the sulphur atom oxidation level. Compounds 4-methyl-3-(p-methoxyphenylsulphonyl) furoxan 6c, 3-phenyl-4-phenylsulphonylfuroxan 10, 4-phenyl-3-phenylsulphonylfuroxan 11 and 3,4-bis(phenyl-sulphonyl)furoxan 12 (EC50 values ranging between 0.055-1.07 microM), seem to be promising since they show the highest potency as well as maximal efficacy, causing complete reversal of noradrenaline induced contraction. The structure-activity relationship, observed in the platelet aggregation test, is substantially similar to that reported for the vasodilating activity, in line with the general profile of these drugs as putative NO-mimetic derivatives.

Modulation of arachidonic acid metabolism by orally administered morniflumate in man

Unlike other classic NSAIDs, some fenamates given at therapeutic concentrations, have been shown to inhibit, both in vitro and in vivo, the 5-lipoxygenase pathway of arachidonic acid cascade as well as the synthesis of cyclooxygenase products. This dual inhibitory property might represent an improvement in anti-inflammatory therapy. The aim of this work was to characterize the effect of morniflumate, administered at therapeutic dosages to normal human volunteers, on leukotriene B4 (LTB4) and thromboxane (TXB2) synthesis, both in purified PMNs and in whole blood. PMNs, isolated two hours after a single oral administration of morniflumate and at steady-state condition, fully retain their capacity to release LTB4 and TXB2. Since intracellular concentrations of the drug were undetectable, in spite of its elevated concentrations in platelet poor plasma, the results obtained using PMNs suggest a drug loss during the cells purification procedure. In whole blood experiments, morniflumate reduced blood LTB4 synthesis induced by Ca-ionophore A23187 Bx approximately 50%, both after single dose and at steady state; the degree of inhibition showed a pattern similar to the plasma levels of the bioactive metabolite of morniflumate (M1). The inhibition of serum TXB2 levels was higher than 85%. Hence, morniflumate is capable of reducing arachidonic acid metabolism acting both on cyclooxygenase and 5-lipoxygenase. This characteristic might provide a better approach in anti-inflammatory therapy.

Pharmacological activity of bamifylline on lung anaphylaxis: in vitro studies

Bamifylline, a 7-8 disubstituted theophylline derivative, reduces in a dose dependent way (1 x 10(-5) M, 1 x 10(-4) M and 1 x 10(-3) M) the release of histamine, TXB2 (measured also as TXA2-like material) and SRS-A (as LTD4-like material) during the immunological challenge of actively sensitized guinea-pig lungs perfused in vitro. Theophylline was significantly less potent than bamifylline and particularly, at the higher concentrations used (1 x 10(-3) M), bamifylline was 2.7 times more potent than theophylline in reducing the immunological release of histamine and 1.6 and 1.5 times more potent in inhibiting the production of TXB2 and SRS-A, respectively. These data suggest that the ability of the two xanthine derivatives to control the immunological release of histamine represents an important point in understanding the mechanism of their anti-anaphylactic activity.

Lack of cardiostimulant effects of bamifylline in in vitro and in vivo models

The cardiac effects of bamifylline (Bamifix), an alkylxanthine derivative, were evaluated on in vivo and in vitro cardiac preparations and compared with those of theophylline and enprofylline. In isolated rat and guinea-pig right atria bamifylline, in contrast to the other xanthines, left the rate of contraction unchanged or reduced it. In isolated rat and guinea-pig left atria the compound induced only slight inotropic effects showing an intrinsic activity significantly lower than that of theophylline and enprofylline. In isolated rabbit papillary muscles bamifylline administration was without effect up to 10(-3) mol/l and decreased the contractile force at a higher concentration, while theophylline dose-dependently increased inotropism. Also in anaesthetized rabbits intravenous administration of bamifylline produced negative chronotropic and dromotropic effects that were associated, at the highest dose, with a reduction of myocardial contractility. Theophylline and enprofylline, at the same equimolar doses, induced positive chronotropic and inotropic effects. The results show that bamifylline is devoid of cardiostimulant effects in respect to other xanthine derivatives. Moreover, they suggest that bamifylline acts on cardiac muscle by a mechanism, probably linked to the Ca+(+)-movements across the cardiac membrane, able to outweigh the effects due to its antiphosphodiesterase activity.

[Derivatives of pyrimidine 1,2-condensate. IV. Synthesis and pharmacological properties of the N,N-disubstituted 4-amino-2H-pyrido(1,2-a)pyrimidin- 2-ones and 2-amino-4H-pyrido(1,2-a)pyrmidin-4-ones]

The N,N-disubstituted 4-amino-2H-pyrido[1,2-a]pyrimidin-2-ones (III) and isomer 2-amino-4H-pyrido[1,2-a]pyrimidin-4-ones (IV) were obtained from the reaction of 2-aminopyridine with the N,N-disubstituted ethyl malonamate/phosphorus oxychloride reagent (II), in refluxing 1,2-dichloroethane. 2-[(N-Benzyl, N-ethyl)amino]derivative (IV b) was also prepared in excellent yield by treating 2-chloro-4H-pyrido[1,2-a]pyrimidin-4-one (V) with N-ethylbenzylamine. Finally, hydrogenation (Raney Nickel) of 4-[(N-ethyl,N-phenyl)amino]-2H-pyrido[1,2-a]pyrimidin-2-one (III e) afforded 6,7,8,9-tetrahydroderivative (VI) which in turn was treated with potassium borohydride to give 1,6,7,8,9,9a-hexahydroderivative (VII). Several compounds described in the present paper, along with some other compounds (III) and (IV) previously synthesized by us (1,2), were tested for various pharmacological activities. The antiallergic activity (PCA in the rat), even though found in several compounds examined, turned out to be submaximal in any case, in spite of the high dose administered (500 mg/kg p.o. as a rule). The most active compound (the activity being estimated at 0.42 times that of thiaramide hydrochloride) was the 4-aminoderivative (III e). The 2-aminoderivatives (IV) series, was found to have marked antiinflammatory properties (carrageenin oedema in the rat); nevertheless, this activity was related to toxic symptoms with the exception of compound (IV b), almost asymptomatic at the administered dose (200 mg/kg p.o.). Moreover the 2-aminoderivatives (IV) generally showed weak adrenolitic activity in vitro (rat seminal vesicles), which was estimated to be from 100 to 1000 times less than that of phenoxybenzamine.

New pharmacological data on the bronchospasmolytic activity of bamifylline

Resistance to lung inflation and blood pressure were monitored together with biological and radioimmunological determination of circulating thromboxane A2 (TxA2) in anaesthetized guinea-pig. Bamifylline, a 2-benzyl-[4,5-d]-imidazopyrimidine derivative, and theophylline were compared for their antagonistic activity against the pulmonary effect of histamine (0.05 mumol/kg i.v.), leukotriene C4 (LTC4, 0.016 mumol/kg i.v.), platelet-activating factor (PAF, 0.0002 mumol/kg i.v.) and acetylcholine (0.1 mumol/kg i.v.). Bamifylline, as well as theophylline, showed a dose-dependent antagonistic activity against both bronchoconstriction and TxA2 generation induced by the above agonists. However, except for histamine where the two compounds were equiactive, bamifylline was 2 times more potent than theophylline. The maximal inhibitory activity was found against bronchoconstriction induced by PAF (ED50 = 6.5 mumol/kg i.v.) followed by histamine (ED50 = 9.5 mumol/kg i.v.), acetylcholine (ED50 = 24.3 mumol/kg i.v.) and LTC4 (ED50 = 31.6 mumol/kg i.v.). Bamifylline (3, 10, 30, 100 mumol/kg i.v.) and theophylline (3, 10, 30, 100 mumol/kg i.v.) protected guinea-pig from antigen-induced bronchoconstriction and TxA2 generation in ovalbumin actively sensitized animals. Also in this series of experiments bamifylline was more potent than theophylline, the ED50 being 9.3 mumol/kg i.v. and 22.9 mumol/kg i.v., respectively. These pharmacological data represent new support for the protecting effect of bamifylline against respiratory damage induced by well known anaphylaxis mediators.

Cardiovascular effects of nicardipine in anesthetized open-chest dogs in the absence and presence of beta-adrenergic receptor blockade: a comparison with nifedipine and verapamil

Nicardipine, a new 1,4-dihydropyridine calcium-entry blocker, was assessed for cardiovascular effects against nifedipine and verapamil in anesthetized open-chest beagle dogs, in the absence and presence of beta-adrenoceptor blockade (propranolol 1 mg/kg i.v.). In control conditions, intravenous nicardipine and nifedipine (30 nmol/kg) produced decreases in blood pressure of similar magnitude without evidence of cardiodepression. An equihypotensive dose of verapamil (300 nmol/kg), by contrast, induced long-lasting negative chronotropic and inotropic effects, which, when combined with the effects of propranolol, were so marked as to cause the death of two of five dogs (atrioventricular block). Dihydropyridine derivatives at higher doses (100 nmol/kg) produced different responses: nifedipine depressed cardiac performance significantly more than nicardipine and, in the presence of beta-adrenergic blockade, caused the death of three of six dogs due to cardiovascular failure. In the nicardipine group, on the contrary, cardiac function was adequately preserved even in the presence of beta-blocker, and no animals died. The results of the present study confirm a previous in vitro observation: nicardipine is a calcium-entry blocker devoid of remarkable cardiodepressant effects and particularly selective for the vascular smooth muscle.

Regional vasodilating and cardiac effects of nicardipine in anaesthetized open chest dog

In this study the effects of intravenous nicardipine on the cardiovascular system in anaesthetized open chest dogs were assessed. In the dose range of 3-30 nmol/kg it induced a dose-dependent and long lasting reduction of the vertebral, coronary and femoral vascular resistance. Nicardipine proved to be equipotent, but longer lasting than nifedipine, and about 10 and 100 times more potent than verapamil and papaverine respectively. Unlike papaverine, calcium entry blockers caused a preferential vasodilation of the vertebral and coronary arteries. Hypotension and a reduction of LVSP and dP/dt appeared only at the highest dose tested. However, for both dihydropyridine derivatives, in contrast to verapamil, the cardiodepressant effects were short-lived and resulted less marked for nicardipine than for nifedipine.

Beta-adrenoceptor and cyclo-oxygenase block as a tool for evoking the direct bronchoconstrictor effect of leukotriene C4 in the guinea-pig

The intravenous administration of LTC4 to anaesthetized guinea-pigs induced dose-dependent bronchoconstriction, which was maximal at the dose of 1.6 nmol kg-1. The response was abolished by indomethacin. The maximal dose of LTC4, preceded by both (-)-propranolol and indomethacin, induced maximal, slow in onset and reversible broncho-constriction. This direct effect of LTC4 was markedly and long-lastingly antagonized by FPL-55712. The beta-blocker did not appreciably affect the systemic blood pressure changes induced by LTC4. The procedure described is suggested as a suitable tool for investigating the per se effect of leukotrienes on the guinea-pig airways in vivo, as well as the efficacy of their receptor antagonists.

In vitro effects of nicardipine on vascular and cardiac muscle preparations

Nicardipine, a new 1,4-dihydropyridine derivative with Ca++-antagonist activity, was tested on rabbit aortic strips contracted with K+ and NA, and on an isolated guinea pig heart perfused at constant flow. It inhibited K+-contraction in the aortic strips and reduced coronary resistance with the same potency as nifedipine resulting about 10 time less potent than the latter in depressing the myocardial contractility. The effects of nicardipine appear to be related essentially to its Ca++-antagonist activity rather than to any antiphosphodiesterase activity.

Beta 2-adrenoceptor blockade is the basis of guinea-pig bronchial hyper-responsiveness to leukotriene C4 and other agonists

Four beta-adrenoceptor antagonists, namely (-)-propranolol, (+)-propranolol, ICI-118551 and (+/-)-practolol, were investigated for their effects on leukotriene C4 (LTC4)-induced bronchoconstriction in the anesthetized guinea-pig. (-)-Propranolol was also investigated for its effects on acetylcholine and histamine bronchospasm in the anaesthetized guinea-pig, and on LTC4-induced contractions of guinea-pig isolated trachea and lung parenchyma. The various beta-adrenoceptor antagonists potentiated, dose-dependently, the bronchoconstriction induced by threshold doses of LTC4 and the intensity of the potentiation correlated with the beta 2-blocking capacity possessed by the drugs. (-)-Propranolol potentiated the bronchospasm induced by threshold doses of acetylcholine and histamine but to a lesser degree than the LTC4-induced bronchospasm. The airway hyper-responsiveness induced by (-)-propranolol was unaffected by pretreatment with mepyramine, cyproheptadine, phenoxybenzamine, atropine or indomethacin. The airway hyper-responsiveness induced by (-)-propranolol persisted even in adrenalectomized or reserpine-treated guinea-pigs, although adrenalectomy induced some increase in airway responsiveness. (-)-Propranolol had no effect on LTC4, histamine and acetylcholine-induced contractions of isolated trachea and lung parenchyma. The results show that the airway hyper-responsiveness induced by beta-adrenoceptor antagonists generally correlates with their beta 2-blocking activity. The possibility remains that some other unknown mechanism(s) may also be implicated.

Investigation of the activity of bronchodilators using a simple but accurate inhalation procedure: forced insufflation

A simple but accurate inhalation procedure for investigating the activity of antiasthmatic drugs is proposed. The procedure consists of the forced insufflation of the powdered drug, blended with micronised lactose, direct into the tracheobronchial tree. Beta-adrenoceptor agonists (isoproterenol and fenoterol) and antimuscarinics (atropine and ipratropium bromide) were tested using the method of Konzett and Rössler in the guinea-pig; their bronchodilator effects were tested both after forced insufflation and after intravenous administration. The proposed inhalation method supplied close-response curves qualitatively comparable to those obtained by the intravenous route, with the added advantage of more detailed information on the time-course effect. Forced insufflation may be the best procedure for investigating antiasthmatic drugs intended for use as inhalants.

Quantification of the synergism between fenoterol and ipratropium bromide in the counteraction of experimental bronchospasm

The interaction between the beta 2-agonist fenoterol and the antimuscarinic ipratropium bromide in the counter-action of experimental bronchospasm in the guinea-pig was studied qualitatively and quantitatively. Finney's analysis showed a significant overadditive interaction between the two constituents of the association, the 'overadditivity factor' being 2.15 if calculated on the peak activity or 2.68 if calculated on the area under the curve inhibition-time. In addition, the combination possesses both of the advantages of the two components, namely rapid onset of action (characteristic of the beta-agonist) and long duration of action (characteristic of the antimuscarinic). A study of the principal cardiovascular and hemodynamic parameters in the cat ruled out any synergism between the two drugs at these levels.

[Phenoxybenzamine antagonism of ergometrine-induced increase of coronary artery resistance in rabbits]

Ergometrine is currently used as a test for Prinzmetal variant angina, causing specifically a coronary artery spasm in these patients, even if the mechanism of this drug on coronaries is still unclear. In isolated rabbit heart perfused at constant flow the administration of ergometrine at the concentration of 2.2 x 10(-5) M evoked a marked and longlasting increase of coronary resistance which was revealed by a rise in perfusion pressure from 68.2 +/- 12.9 to 124.4 +/- 21.7 (m +/- SD; n=21). This increase appears only with repeated perfusions of the drug and moreover it was not reproducible in the same preparation after its maximal response. The vasoconstriction was not significantly affected either by atropine or mepyramine, but it was strongly reduced by the phenoxybenzamine pretreatment (2.9 x 10(-6) M; n=8). It is evident the role of alpha-adrenergic receptors in ergometrine effect, but our results do not allow to understand its true mechanism, in fact the noradrenaline release can not be completely excluded.

Influence of contrast media osmolality on isolated rabbit heart performance

A low osmolality contrast medium (Iopamidol) caused less cardiac disturbance on isolated rabbit heart than a high osmolality medium (Urografin). The same effects were induced by glucose solutions iso-osmolal with the two media. After perfusion with Propranolol (1 microgram/ml) and Cimetidine (1 microgram/ml) the observed effect was unaltered.

Cardiovascular effects induced by the injection of a new nonionic contrast medium (Iopamidol): experimental study in dogs

The hemodynamic effects induced by the injection in the pulmonary artery of the new nonionic water soluble contrast medium Iopamidol were compared with those obtained by the injection of two other currently used contrast media (meglumine diatrizoate and sodium iothalamate). The experiments were carried out in nine mongrel dogs. Hemodynamic variables were continuously measured prior to, during, and for 8 minutes after injection of the contrast media. Injections of iopamidol produced significantly smaller decreases in aortic pressure (p less than 0.01), contractile indices (p less than 0.01), and peripheral resistances (p less than 0.01), and changes in heart rate and in cardiac output were less pronounced. At 3-4 minutes after injection, an increase in Vmaxd was observed with all three contrast media, but it was significantly lower after injecting Iopamidol. The role of hyperosmolality in causing cardiovascular changes is discussed. The less significant changes induced by Iopamidol appear to be the result of its lower osmolality, which is about a third that of meglumine diatrizoate or sodium iothalamate.

Effect of ergometrine on contractile force of guinea-pig isolated heart: antagonism by cimetidine

The action of ergometrine on contractile force of guinea-pig isolated heart was investigated and the effect of receptor antagonists on the inotropic effect of ergometrine, isoproterenol, dopamine and histamine was evaluated. Ergometrine was found to have a good dose-dependent inotropic effect and the antagonism of cimetidine toward this action is reported. Experiments carried out in hearts in which a massive depletion of mast-cells histamine was produced are in favour of a direct action of the drug on H2-receptors.