A-77636: a potent and selective dopamine D1 receptor agonist with antiparkinsonian activity in marmosets

A-77636, ((1R,3S) 3-(1'-adamantyl)-1-aminomethyl-3,4-dihydro-5,6-dihydroxy-1H-2-benz opyran hydrochloride), is a selective dopamine D1 receptor agonist. In a battery of receptor binding assays, A-77636 shows the highest affinity (pKi = 7.40 +/- 0.09; Ki = 39.8 nM) for the dopamine D1 receptor. A-77636 is an agonist at the dopamine D1 receptors in the fish retina (pEC50 = 8.13; EC50 = 1.1 nM; intrinsic activity = 102% of dopamine) and the rat caudate-putamen (pEC50 = 8.97; intrinsic activity = 134% of dopamine). The compound is functionally inactive at dopamine D2 receptors (EC50 > 10 microM). In rats with unilateral 6-OHDA (6-hydroxydopamine) lesions of the nigro-striatal dopaminergic pathway, A-77636 elicits prolonged (> 20 h) contralateral turning that is blocked by SCH 23390, a D1 receptor antagonist, but not by haloperidol at doses selective for the dopamine D2 receptor. Higher doses of A-77636 produce forelimb clonus in rats and mice. When tested in marmosets treated with MPTP to induce a parkinsonian-like state, A-77636 increases locomotor activity and decreases the severity of the parkinsonian-like symptoms: the compound is active after either subcutaneous or oral administration. A-77641, the optical antipode of A-77636, has a lower affinity towards the dopamine D1 receptor (pKi = 5.14, Ki = 7200 nM), is less potent as a dopamine D1 receptor agonist (pEC50 = 5.65; EC50 = 2200 nM), fails to elicit turning in the 6-OHDA-lesioned rat, and lacks antiparkinsonian efficacy in the MPTP-treated marmoset.(ABSTRACT TRUNCATED AT 250 WORDS)

Duration of antiestrogenecity of compound CDRI-85/287: a new orally active nonsteroidal antiimplantation agent

Duration of antiestrogenic and antiimplantation action of CDRI-85/287, (2-(4-(2-N-piperidino)ethoxy phenyl)-3-phenyl(2H)benzo(2)pyran), was studied in rat. Pretreatment of ovariectomized immature rats with this compound caused translocation of cytoplasmic estrogen receptor (ER) to the nucleus and a marked depletion of cytoplasmic ER pool resulting in a nonresponsive state of the uterus to subsequent estrogen administration until day 4. While in rats pretreated with estradiol, increased cytoplasmic ER level made the uterus responsive to a second injection of estrogen. In the delayed implantation model, 85/287 pretreated rats were given estrone on days 4, 5 or 6 post-antiestrogen treatment. No implantations were observed after estrone administration on day 4, but were present when estrone was given on days 5 or 6. Summation of these results suggests the duration of action of 85/287 to be 3-4 days in rat.

Systemic tumor necrosis factor-alpha production in experimental colitis

Tumor necrosis factor-alpha (TNF) is a cytokine released by mononuclear cells in response to inflammation and sepsis. Since the biological effects of TNF are consistent with the systemic and intestinal features of ulcerative colitis, the role of TNF was examined in a rabbit model of chronic colitis. Peripheral blood mononuclear cells were isolated, stimulated with lipopolysaccharide, and cultured supernatants assayed for TNF levels using a cytotoxic assay on mouse fibrosarcoma L929 cells. Basal levels of TNF production by mononuclear cells from 13 normal rabbits (124.3 units/ml +/- 27.1 units/ml, mean +/- SE) were not different from nine rabbits with colitis (83.6 units/ml +/- 24.4 units/ml, P > 0.05). Treatment with lipopolysaccharide (100 micrograms/ml) induced increased TNF production by mononuclear cells isolated from both normals (672.0 units/ml +/- 197.5 units/ml, P < 0.05) and rabbits with colitis (1114.0 units/ml +/- 489.6 units/ml, P < 0.05). However, at all lipopolysaccharide concentrations stimulated TNF levels were comparable in experimental and control groups (P > 0.05). In light of the role of leukotrienes in inflammation, a separate group of rabbits with colitis was investigated following treatment with an oral leukotriene B4 receptor antagonist. Serum TNF levels in 15 control rabbits (32.5 units/ml +/- 7.6 units/ml, mean +/- SE) were not significantly different from rabbits with colitis receiving either leukotriene B4 receptor antagonist (35.7 units/ml +/- 9.2 units/ml, N = 13) or vehicle alone (50.3 units/ml +/- 10.2 units/ml, N = 14) (ANOVA, P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Cross tolerance between cromakalim and RP49356 in the uterus of the rat in vivo and in vitro

We investigated tolerance to the potassium (K+) channel openers, cromakalim and RP49356 and cross tolerance between them in the uterus of the rat. Continuous infusion of RP49356 in vivo produced 5.2-fold (200 or 300 micrograms/kg per h) and 7.2-fold (600 micrograms/kg per h) desensitization of the uterus to RP49356. Uterine sensitivity to RP49356 was reduced 7.4-fold in cromakalim-tolerant rats and sensitivity to cromakalim was reduced 7.9-fold in RP49356-tolerant rats. Incubation of isolated uterus with 10 microM cromakalim for 4 h reduced uterine sensitivity to cromakalim by about 45-fold and to RP49356 by 2.1-fold but did not alter sensitivity to salbutamol. Incubation with 10 microM RP49356 for 4 h reduced sensitivity to RP49356 by 2.5-fold and to cromakalim by 3.8-fold. Occurrence of uterine tolerance to K+ channel openers in vitro suggests that tolerance in vivo has a pharmacodynamic basis. Cross tolerance between cromakalim and RP49356 provides evidence that these two K+ channel openers possess common binding sites and/or mechanism(s) of action. However, the greater extent of self-tolerance to cromakalim than to RP49356 suggests a difference in their actions.

Relationship between the sympatholytic action of nebivolol and hypotension

Nebivolol, a chemically novel beta 1-adrenoceptor antagonist, acutely lowers blood pressure in spontaneously hypertensive rats, anaesthetised normotensive dogs, and hypertensive patients. We have investigated the actions of dl-nebivolol in five conscious normotensive rabbits (sham, mean blood pressure (BP) of 82.2 +/- 4.1 mm Hg, mean +/- SEM) and four hypertensive rabbits (renal wrap hypertension) (wrap, mean BP of 117.6 +/- 1.5 mm Hg). Nebivolol (1 mg/kg i.v.) did not significantly lower the BP or heart rate in either group 30 min after injection. In the same rabbits, on another day, after autonomic blockade (mecamylamine), nebivolol (0.1, 0.3, and 1.0 mg/kg i.v.) right shifted the bolus i.v. isoproterenol tachycardia dose-response curves by dose ratios of 5, 18, and 90 in sham rabbits, respectively, and 5, 11, and 23 in wrap rabbits, respectively, indicating significant cardiac beta 1-adrenoceptor antagonism. In guinea pig isolated right atria pretreated with atropine (1 microM) and desipramine (DMI, 0.1 microM), norepinephrine concentration-response curves were antagonised competitively by nebivolol (3-100 nM), giving a pKb of 7.90. In separate atria without DMI pretreatment, neither nebivolol (100 nM) nor propranolol (100 nM) had any significant effect on the increase in the rate of norepinephrine efflux following electrical field stimulation (0.5-2 Hz, 3 min). These findings suggest that at concentrations of nebivolol that show substantial beta 1-adrenoceptor antagonism, there is no evidence of hypotension or bradycardia nor additional effects on cardiac norepinephrine release. Why nebivolol lowers blood pressure in some species but not in the conscious rabbit is not known.

Comparison of the actions of acetylcholine and BRL 38227 in the guinea-pig coronary artery

1. The contractile and electrical responses to acetylcholine (ACh) in isolated segments of guinea-pig and rabbit coronary arteries were compared to those of the putative adenosine 5'-triphosphate (ATP)-dependent K+ channel opener, BRL 38227. 2. Both ACh and BRL 38227 produced concentration-dependent relaxation of vessel segments contracted with the H1-receptor agonist, 2-(2-aminoethyl)pyridine. 3. An IC90 of either vasodilator also produced 17-20 mV of hyperpolarization of the guinea-pig coronary artery. 4. Glibenclamide (1-35 microM) depolarized the guinea-pig coronary artery by 8-12 mV and antagonized BRL 38227- but not ACh-induced relaxation and hyperpolarization. 5. In the guinea-pig coronary artery, the K+ channel blockers phencyclidine (PCP, 100 microM), tetraethylammonium (TEA, 10 mM) and scorpion venom (8.7 micrograms ml-1) all significantly reduced ACh-induced relaxation and hyperpolarization whereas only PCP was an effective antagonist of both relaxation and hyperpolarization with BRL 38227. 6. Similar effects of glibenclamide and scorpion venom on ACh- and BRL 38227-induced relaxation were observed in the rabbit coronary artery. 7. Apamin (3.5 microM) was without effect on either the ACh- or BRL 38227-induced relaxation in the guinea-pig coronary artery. 8. In conclusion, the actions of BRL 38227 in coronary artery are compatible with its proposed effects on ATP-dependent K+ channels. In contrast, the results with ACh suggest that some step between the initial binding of ACh to endothelial muscarinic receptors and the final relaxation of the smooth muscle depends upon the opening of Ca(2+)-activated K+ channels.

Antidiabetic agent englitazone enhances insulin action in nondiabetic rats without producing hypoglycemia

The new antihyperglycemic agent englitazone (CP-68,722) was examined in nondiabetic rats. Administration of englitazone at 50 mg/kg/d for 8 days did not produce overt hypoglycemia but it lowered basal plasma insulin by 59% and 41% in rats fed ad libitum and fasted overnight on the last day, respectively. Drug treatment also lowered (P less than .05) plasma nonesterified fatty acids (1.09 +/- 0.05 to 0.36 +/- 0.05 mmol/L) and cholesterol (2.41 +/- 0.08 to 2.06 +/- 0.07 mmol/L) in fasted rats, and glycerol (0.25 +/- 0.02 to 0.14 +/- 0.02 mmol/L) in fed rats but had no effect on 3-hydroxybutyrate or lactate levels despite the hypoinsulinemia. Disposition of an oral glucose load (1 g/kg) in drug-treated fed rats was identical to that in control rats despite a 40% reduction in the area under the plasma insulin curve. Insulin-stimulated 2-deoxy-D-3H-glucose uptake was significantly (P less than .05) enhanced in adipocytes prepared from both fasted and fed drug-treated rats (0.56 +/- 0.07 to 0.84 +/- 0.03 and 0.79 +/- 0.02 to 1.00 +/- 0.02 nmol/5 min, respectively, at insulin concentration of 2,500 microU/mL). There was also a significant increase in the basal rate of 2-deoxyglucose uptake (0.07 +/- 0.01 to 0.24 +/- 0.07 nmol/5 min) in adipocytes from fasted rats only. Insulin-stimulated lipogenesis from 3H-2-glucose was enhanced in adipocytes from drug-treated fed rats (7.72 +/- 0.09 to 10.19 +/- 0.10 nmol glucose/45 min at insulin concentration of 2,500 microU/mL) but no effect was observed in adipocytes from fasted rats (2.57 +/- 0.30 to 2.33 +/- 0.16 nmol glucose/45 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of short-term administration of cromakalim on renal hemodynamics and eicosanoid excretion in essential hypertension

Cromakalim, a novel potassium channel-activating drug, was administered for a 3-day period in eight untreated hospitalized patients with established hypertension. The fixed and single dose of 1.5 mg/day produced a significant reduction in systolic and diastolic blood pressure with a small increase in heart rate. Glomerular filtration rate was unchanged and effective renal plasma flow was slightly increased with a concomitant small decrease in filtration fraction and in renal vascular resistance. No significant change was observed in urinary prostaglandin (PG)E2, PGF2 alpha, and thromboxane B2, while 6-keto-PGF1 alpha (the stable metabolite of prostacyclin) rose from 189 +/- 6 to 368 +/- 115 ng/day. The renal excretion of 6-keto-PGF1 alpha correlates with the modification observed in renal plasma flow, suggesting a compensatory role for prostacylin in preserving renal hemodynamics during antihypertensive therapy with cromakalim.

Influence of nebivolol on the cardiovascular hemodynamics during postural changes and isometric exercise

Nebivolol (R67555), a drug with beta 1 receptor antagonizing properties, was administered once daily (5 mg) for 7 days in 10 healthy volunteers. The hemodynamic parameters were measured noninvasively during postural changes (supine, sitting, standing) and during isometric handgrip at 50% maximal voluntary contraction, before and 3, 8, and 23 hours after the first nebivolol intake of 5 mg; the same measurements were done 23 hours after the last intake. Nebivolol lowered arterial blood pressure acutely and chronically due to a decrease in heart rate and cardiac output. The stroke volume seemed to be preserved, while the total peripheral vascular resistance did not change. Nebivolol did not change the orthostatic responses, except that the absolute value was lowered. Nebivolol was unable to prevent the blood pressure increase during isometric handgrip. However, this blood pressure increase was obtained by an increase in the total peripheral vascular resistance and not by an increase in the cardiac output, as observed during control measurements before nebivolol intake.

MCD peptide and dendrotoxin I activate c-fos and c-jun expression by acting on two different types of K+ channels. A discrimination using the K+ channel opener lemakalim

Mast cell degranulating (MCD) peptide and Dendrotoxin I (DTXI), two potent hyperexcitability-inducing toxins acting on voltage-dependent potassium channels, induce the expression of both c-fos and c-jun mRNA in i.c.v. treated rats. The distribution of c-fos and c-jun expression has been analyzed by in situ hybridization. The expression is particularly high in the cerebral cortex and hippocampus for both toxins. However differences of expression between MCD and DTXI-treated animals have been observed in hypothalamus and thalamic and amygdaloid nuclei. Moreover, brain areas such as cerebellum which have high amounts of binding sites for both MCD and DTXI do not show any induction of c-fos and c-jun. Lemakalim, a K+ channel opener, prevents the MCD-induced activation of both 'immediate-early genes' in all brain areas but is unable to inhibit the induction of c-fos and c-jun induced by DTXI. These two toxins which are generally believed--from molecular approaches--to act on the same voltage-dependent K+ channel, clearly act in vivo on two distinct classes of channels.

Cardiovascular effects of intracerebroventricular injections of (+/-)-nebivolol and its enantiomers--a comparison with those of metoprolol in the rat

The cardiovascular effects of (+/-)-nebivolol, a potent beta 1-adrenoceptor antagonist, and its enantiomers, (+)-nebivolol (SRRR) and (-)-nebivolol (RSSS) in normotensive anaesthetized rats, have been investigated using metoprolol as a reference substance. The drugs decreased blood pressure and heart rate immediately after i.c.v. injection. These effects paralleled the beta-blocking potencies ((+)- greater than (+/-)-greater than (-)-nebivolol). Metoprolol induced a weaker hypotension than (+/-)-nebivolol, and a long-lasting reduction in stroke volume. As reported after i.v. administration, (+/-)-nebivolol and isomers by the i.c.v. route decreased peripheral vascular resistance following i.c.v. administration while metoprolol increased it. These effects are centrally mediated since cardiovascular responses to isoprenaline i.v. remained unchanged.

Effects of a new compound (Zy 15850A) on cigarette smoke-induced bronchitis in the rat

The effect of 4H-4 phenylthieno-(3,2-C)-(1)-benzopyran-2-carboxylate (Zy 15850A) on mucous cell hyperplasia was examined in vivo using a well established rat model of cigarette smoke-induced bronchitis. Zy 15850A was given by gavage (25 mg/kg body weight) to male rats before and after sub-acute exposure (i.e. daily for 14 days) to an atmosphere of cigarette smoke (CS). CS significantly increased the thickness of the epithelium at three of the four sites studied in the trachea and in both of the intrapulmonary levels examined. CS increased the number of epithelial mucous cells in all intrapulmonary airways and also increased the mass of submucosal gland present in the larynx and upper trachea. Zy 15850A completely inhibited CS-induced increases in epithelial thickness in the upper trachea and the two intrapulmonary airway levels studied, and tended to inhibit CS-induced epithelial mucous cell hyperplasia in all the six intrapulmonary airway levels examined, with statistically significant inhibition in two. Zy 15850A had no inhibitory effect of the CS-induced enlargement of laryngo-tracheal submucosal glands. We conclude that, in the rat, the predominant inhibitory effect of Zy 15850A is on CS-induced epithelial thickening with weaker inhibitory effects on mucous cell hyperplasia and enlargement of submucosal glands. Zy 15850A is less effective than other mucoregulatory drugs or antiinflammatory agents we have tested in the same bronchitic model.

Cardiovascular effects of cromakalim (BRL 34915) in healthy volunteers

1. The effect of oral doses of cromakalim 0.5, 1.0, 1.5 and 2.0 mg on several cardiovascular parameters was studied in healthy male volunteers. 2. In the first study, no dose of cromakalim reduced systolic or diastolic blood pressure in the supine or standing position. Reductions of diastolic blood pressure after exercise (P less than 0.01) were observed 4 h after administration of 2.0 mg. 3. There was a trend towards increased heart rate after 2.0 mg at all time intervals, and significant changes were observed in supine and standing heart rate at 2 and 4 h (P less than 0.01). No significant change was observed in exercise heart rate. 4. In the second study small increases in forearm blood flow were observed from 3 h to 5 h after oral administration of 1.0 and 2.0 mg of cromakalim. Forearm vascular resistance was significantly reduced after 2.0 mg (P less than 0.025) when compared with placebo. No change was observed in forearm venous capacitance after either dose of cromakalim, or placebo. Supine heart rate was significantly increased 4 h after 2.0 mg of cromakalim (P less than 0.025). 5. These results show that oral administration of cromakalim decreases diastolic blood pressure and forearm vascular resistance. A hypotensive effect is probably attenuated by reflex tachycardia.

Activation of ATP-sensitive K channels by a K channel opener (SR 44866) and the effect upon electrical and mechanical activity of frog skeletal muscle

To examine the effects of the activation of adenosine 5'-triphosphate (ATP)-sensitive K channels in a skeletal muscle we have applied the ATP-sensitive K channel opener SR44866 whilst recording single ion channels, voltage-clamped membrane currents, evoked action potentials and tension in sartorius muscles of the frog. In excised inside-out membrane patches SR44866 opened channels which could be inhibited by internal ATP and glibenclamide. In voltage-clamped individual muscle fibres SR44866 evoked a glibenclamide-sensitive membrane current which reversed at -70 mV. The effect of SR44866 was dose dependent with an effective concentration for 50% maximal effect (EC50) of 67 microM and a slope factor of 2. SR44866 dose dependently reduced the duration of the spike after-potential, spike overshoot, Vmax, tetrodotoxin-sensitive voltage-gated inward membrane currents and muscle twitch tension. From this evidence it can be concluded that the opening of ATP-sensitive K channels may be associated with the inhibition of contraction of skeletal muscle.

Inhibition by Ro 31-6930 of agonist and allergen induced bronchoconstriction in anaesthetised guinea-pigs and cats

Ro 31-6930, a potent smooth muscle relaxant from the novel class of potassium channel openers, has been compared with BRL 38227, salmeterol and theophylline in a range of models of airway function. Ro 31-6930 relaxed isolated tracheal muscle from sensitised guinea-pigs which had been contracted by ovalbumin and was equipotent with salmeterol in inhibiting antigen-induced bronchospasm in anaesthetised, sensitised guinea-pigs. In both anaesthetised guinea-pig and cat, Ro 31-6930, BRL 38227 and theophylline were more potent against 5-HT evoked increases in lung resistance than they were on falls in dynamic compliance. Although salmeterol had equivalent activity on both parameters it is unlikely that the small difference seen with the other compounds reflect a preferential effect on large airways. In addition, Ro 31-6930 was an effective bronchodilator when given by inhalation to the anaesthetised guinea-pig. In view of the protective activity of Ro 31-6930 against antigen challenge in the sensitised guinea-pig and its potency in relation to other bronchodilators, it is considered that compounds which relax airway smooth muscle by the opening of plasmalemmal potassium channels may have a role in the treatment of asthma.

Stereoselective acyl glucuronidation and glucosidation of pranoprofen, a 2-arylpropionic acid derivative, in mice in vivo

Following the oral administration of RS(+/-)-pranoprofen to mice at a dose of 25 mg/kg, 10.7% of the acyl glucuronide and 46.4% of the acyl glucoside of pranoprofen were excreted in the urine within 24 h. The recovery of acyl glucoside in the urine decreased relative to that of acyl glucuronide at increasing doses (100, 200 mg/kg). Following the oral administration of S(+)-pranoprofen to mice at a dose of 25 mg/kg, 5.0% of the acyl glucuronide and 56.5% of the acyl glucoside were excreted in the urine within 24 h, while 10.8% of the acyl glucuronide and 13.9% of the acyl glucoside were excreted after the oral administration of R(-)-pranoprofen, respectively. The absolute configuration of the aglycone of acyl glucuronide was almost R(-)-enantiomer (92.5-96.1%) in the 0-24 h urine, whereas that of acyl glucoside contained 15.3-24.7% of S(+)-enantiomer after the oral administration of R(-)-pranoprofen. On the other hand, only the S(+)-isomer was found as the aglycone of both acyl glucuronide and glucoside after the oral administration of S(+)-pranoprofen. The present results showed that stereoselective conjugation was observed in glucosidation in mice. Nevertheless, a dose-dependent shift in glucuronidation and glucosidation was found for both the administrations of S(+)- and R(-)-enantiomers as well as RS(+/-)-pranoprofen. Also a chiral inversion of R(-)-enantiomer to S(+)-antipode may occur slightly but significantly in mice.

Dose-dependent shift in acyl glucuronidation and glucosidation of pranoprofen, a 2-arylpropionic acid derivative, in mice in vivo

Following the oral administration of [14C]pranoprofen to mice, 70-80% of radioactivity was excreted in the urine, and 15-25% in the feces within 3 d at 5, 25, 50, 100 and 200 mg/kg. This showed that no significant change in urinary and fecal excretion was observed among these doses. The radioactivity levels in the blood also increased in proportion to the doses, indicating that no repression of the absorption of pranoprofen was found even at increased doses. The major metabolites in mouse urine were acyl glucuronide and the glucoside of pranoprofen. At low doses acyl glucoside was predominantly excreted in urine, whereas acyl glucoside decreased relative to acyl glucuronide at increased doses. Although 43.2% of the acyl glucoside was recovered in the 24 h urine samples after the intravenous administration of acyl glucuronide, no acyl glucuronide was found in the urine after the intravenous administration of acyl glucoside. These results demonstrated the interesting observation that pranoprofen had a preference for glucosidation rather than glucuronidation in mice at low doses in spite of having a higher capacity of glucuronidation.

Haemodynamic profile of the potassium channel activator EMD 52692 in anaesthetized pigs

1. The systemic and regional haemodynamic effects of the potassium channel activator EMD 52692 or its solvent were investigated after intravenous and after intracoronary administration in anaesthetized pigs. 2. Consecutive intravenous 10 min infusions of EMD 52692 (0.15, 0.30, 0.60, 1.20 micrograms kg-1 min-1; n = 7) dose-dependently decreased mean arterial blood pressure by up to 50%. This was entirely due to peripheral vasodilatation, since cardiac output did not change. Heart rate increased by up to 50%, while left ventricular end diastolic pressure decreased dose-dependently from 6 +/- 1 mmHg to 3 +/- 1 mmHg (P less than 0.05), and stroke volume decreased from 30 +/- 2 ml to 21 +/- 2 ml (P less than 0.05). Left ventricular dP/dtmax was not affected. 3. Although cardiac output did not change, EMD 52692 caused a redistribution of blood flow from the arteriovenous anastomoses to the capillary channels. Blood flow to the adrenals, small intestine, stomach, bladder, spleen and brain increased, while renal blood flow decreased and blood flow to several muscle groups and skin were not altered. Vascular conductance was increased dose-dependently in all organs, except for the kidneys, where after the initial increase, vascular conductance returned to baseline with the highest dose. Particularly striking were the effects on the vasculature of the brain. With the highest dose of EMD 52692 blood flow more than doubled, while vascular conductance increased four fold. 4. Transmural myocardial blood flow increased slightly, which was entirely due to an increase in subepicardial blood flow. Myocardial O2-consumption and segment length shortening were not significantly affected. 5. After consecutive 10 min intracoronary infusions (0.0095, 0.019, 0.0375 and 0.075 microgram kg-1 min-1; n = 7) into the left anterior descending coronary artery (LADCA), mean arterial blood pressure was maintained with the lowest two doses, but decreased by up to 15% with the higher doses, whereas heart rate increased by up to 24%. Blood flow to the LADCA-perfused myocardium doubled with the highest dose, the subepicardium benefitting the most. Coronary venous O2-saturation increased dose-dependently from 23 +/- 2% to 60 +/- 4%, while myocardial O2-consumption of the LADCA-perfused myocardium was not affected by the drug. 6. It is concluded that EMD 52692 is a potent vasodilator, with particularly pronounced effects on vasculature of the brain. Its selectivity for vascular smooth muscle cells exceeds that for the myocytes, since with doses that are much higher than those of potential clinical interest no negative inotropic effects were observed. The compound primarily dilates arteries but some venodilatation may also occur.

Pulmonary and systemic haemodynamic effects of cromakalim in conditions of normoxia and hypoxia in dogs

1. In anaesthetized-closed chest dogs, exposure to hypoxia (60 min) caused a sustained increase in arterial pulmonary pressures (diastolic: DPP, mean: MPP and effective capillary: EPCP by 132, 66 and 104% respectively) and increased total pulmonary vascular resistance (TPVR, 143%) with minimal changes in systemic haemodynamics. 2. Under normoxia, cromakalim infusion (2 micrograms kg-1 min-1 for 30 min) progressively decreased diastolic systemic arterial pressure (DBP, 30%) and total systemic vascular resistance (TSVR, 54%). In contrast, DPP was increased by 45%, due to an increase in cardiac output (CO: 55%), while TPVR was essentially unchanged. 3. Under hypoxic conditions, cromakalim (2 micrograms kg-1 min-1 for 30 min) induced changes in systemic haemodynamics comparable to those seen under normoxia. However, DPP was decreased by 37% at the end of infusion. The compound progressively decreased TPVR in a dose-related manner and PaO2 (55.9 mmHg) was maintained since cardiac output was increased. 4. Thus, under normoxia, cromakalim induced haemodynamic effects on the pulmonary circulation which were directly related to an increase in CO, but were clearly different from those observed under hypoxia. In the hypoxia-induced constricted pulmonary vascular bed, cromakalim effectively reduced the elevated pulmonary vascular resistance at low doses but showed comparable vasodilator effects on the systemic circulation under both conditions. The findings suggest that a vasodilator agent like cromakalim may be useful in patients with respiratory conditions associated with elevated pulmonary vascular resistance.

Attenuation of nocturnal asthma by cromakalim

In a randomised, double-blind, crossover study, single oral doses of cromakalim, a potassium-channel activator, or placebo were given to 23 patients with nocturnal asthma. There was a significant reduction (p less than 0.005) in the early morning fall in forced expiratory volume in 1 s (FEV1) after 0.5 mg cromakalim (fall 9.8% [SEM 3.2%]) compared with placebo (18.5 [2.8]%). In a repeat dosing study, administration of 0.25 mg and 0.5 mg cromakalim on 5 consecutive nights to a further group of 8 asthmatic subjects significantly reduced the early morning fall in FEV1 from 28.7 (6.5)% after placebo to 19 (4.2)% after 0.25 mg and 14.9 (6.5)% after 0.5 mg. Potassium-channel activators may be useful in the treatment of asthma, especially for nocturnal symptoms.

[The pharmacokinetics of pranoprofen in humans]

The pharmacokinetics of pranoprofen, 2-(5H-[1]benzopyrano[2,3-b]pyridin-7-yl) propionic acid (I) in humans were examined. 1-O-Acylglucuronide of I (II) and its isomer (III) were isolated from the human urine after oral administration of I. The stability of II was tested in order to establish the suitable conditions for the storage and handling of biological samples. Maximum stability of II was found at pH 3-4. Unchanged drugs, II and III were detected in the human plasma after oral administration of I. Plasma concentrations of these compounds reached the maximum at 1-2 h after the administration and thereafter decreased biphasically. From the urinary sample, 1-O-acylglucoside of I (IV) was detected in addition to unchanged drugs, II and III. Within 24 h after dosing, 1.3, 84.0, 7.0 and 0.6% of the dose were excreted as I, II, III and IV, respectively and the total urinary excretion amounted to 92.9% in term of unchanged drug.

Ocular toxicity in beagle dogs with lortalamine, a non tricyclic antidepressant compound

During a preclinical safety evaluation study, an indication of ocular toxicity was noted in beagle dogs receiving orally (gelatin capsules) once a day, 7 days a week for, respectively, 7 and 91 days, 10 mg/kg/day of Lortalamine, a new non-tricyclic anti-depressant compound. Lortalamine treated dogs showed, progressively, bilateral mydriasis, conjunctivitis, epiphora, corneal oedema and corneal erosions from day 2 to day 7. Thereafter, even though treatment goes on, ocular lesions were progressively improved, and inflammation and swelling of both cornea slowly reversed, especially from day 8 to 30. These ocular changes were very similar to those reported with sympathomimetic agents. It was speculated that these lesions, following chronic oral administration of Lortalamine which induced high levels of the compound and its metabolite in the cornea, were related to an increased binding of norepinephrine to adrenergic receptors since the compound inhibits the re-uptake of the transmitter into the storing vesicles.

Activity of FCE 20696, a new synthetic immunomodulator, in models of viral and bacterial pathology

The dibenzopyran derivative FCE 20696 is an immunomodulator which protects mice infected with several viral agents and with Mycobacterium tuberculosis. The compound is able to decrease the severity of the lung lesions caused by influenza virus infection. Doses ranging from 12.5 to 100 mg/kg are effective even after a single administration. Activity is demonstrated by intraperitoneal, subcutaneous and oral administration of the drug. In systemic infection with herpes simplex virus type 1, the 100 mg/kg dosage, administered subcutaneously, is able to increase both the percentage and the mean survival time of mice. To have effect by oral administration it is necessary to give the compound twice in the day. Moreover, some activity has also been observed in mice infected by M. tuberculosis, when the compound is administered orally at doses of 1-2.5 mg/kg twice weekly for 5 weeks, during the course of the disease.

Short-term monotherapy with the potassium channel activator BRL 34915 on endocrine sodium regulation in essential hypertension

BRL 34915, a potassium channel-activating drug, was administered for a three-day period in eight untreated and hospitalized patients with established hypertension. The fixed and single dose of 1.5 mg/d produced a significant reduction in systolic and diastolic blood pressure with a small increase in heart rate. Plasma renin activity, plasma and urinary aldosterone, plasma atrial natriuretic peptide (ANP), and serum electrolytes were unchanged during the therapy. Urinary sodium and body weight remained similar throughout the study. These results indicate that short-term administration of an antihypertensive dose of BRL 34915 does not alter the renin-angiotensin-aldosterone and ANP systems. Blood pressure is lowered without secondary sodium retention.