[Changes in platelet production of malondialdehyde in diabetics treated with dilazep]

We have investigated the effect of dilazep on the prostaglandin synthesis determined as indicator malondialdehyde (MDA) formation. Twenty patients with type 2 diabetes, aged 25-65 years were orally given dilazep at 100 mg X 3/day for 56 daily. The platelet activity has valued before and after the treatment with the production of the MDA. We conclude that the dilazep inhibited statistically significant biosynthesis of prostaglandin endoperoxides from arachidonic acid.

[The effect of dilazep on circulating platelet aggregation in diabetics]

The aim of the present paper was to evaluate the effect of the 1,4 bis [3-(3,4,5-trimethoxybenzoyl-oxy) propyl] perhydro-1,4 diazepina (dilazep) on reduction of circulating platelet aggregates in 18 patients with type 2 diabetes, 13 female and 5 male, aged 25-65 years. Dilazep was orally given at 100 mg X 3/day for 8 weeks. The platelet activity has valued before and after the treatment trough the evaluation of circulating platelet aggregates with the method of Wu and Hoak. The results confirmed that the dilazep decreased statistically significant after 8 weeks the circulating aggregates.

The kinetics of dissociation of the inhibitor of nucleoside transport, nitrobenzylthioinosine, from the high-affinity binding sites of cultured hamster cells

Nucleoside transport in various types of animal cells is inhibited by the binding of nitrobenzylthioinosine (NBMPR) to a set of high-affinity sites on the plasma membrane. This work examined the binding of [3H]NBMPR to the nucleoside transporters of cultured Nil 8 hamster fibroblasts and of cells of a virus-transformed clone (Nil SV) derived from Nil 8. Experiments conducted with intact Nil 8 and Nil SV cells and with membrane preparations indicated that the two lines differed significantly in the cellular content of binding sites and only slightly in the affinities of these sites for NBMPR. Nil 8 and Nil SV cells possessed (4.2-8.0) X 10(5) and (2.0-4.0) X 10(6) sites per cell respectively, whereas the dissociation constants of site-bound NBMPR obtained with intact cells and with membrane preparations were similar, ranging from 0.29 to 1.5 nM. Dilazep, a potent inhibitor of nucleoside transport that is structurally unrelated to NBMPR, appeared to compete with NBMPR for binding to the high-affinity sites when tested under equilibrium conditions with Ki values for inhibition of NBMPR binding to Nil 8 and Nil SV cells respectively of 15 +/- 4 and 32 +/- 4 nM. The dissociation of NBMPR from the binding site--NBMPR complex of Nil SV membrane preparations was a first-order decay process with a rate constant of 0.68 +/- 0.26 min-1. The rate of dissociation of NBMPR from the binding-site complex of membrane preparations and intact cells was decreased significantly in the presence of dilazep and increased in the presence of the permeant uridine. These results suggest that the apparent competitive-inhibition kinetics obtained for dilazep under equilibrium conditions should not be interpreted as binding of dilazep to the same site as NBMPR but rather as binding of the two inhibitors to closely associated sites on the nucleoside transporter. Similarly, uridine also appears to bind to a site separate from the NBMPR-binding site.

Dilazep: an inhibitor of adenosine uptake with intrinsic calcium antagonistic properties

Concentrations of dilazep which were ineffective in altering the muscular tone of the guinea-pig taenia caeci (0.03, 0.3 microM) or the phasic mechanical activity of the rabbit proximal ileum (0.03 microM) markedly potentiated the inhibitory action of adenosine on both these parameters. Dilazep, 0.3 microM or greater, dose-dependently inhibited the mechanical activity of the proximal ileum. This inhibitory action was probably mediated by more than one mechanism, as shown by the fact that theophylline (50, 100 microM) antagonized the effect at lower dilazep concentrations (up to 3 microM) leaving essentially unchanged the response to higher concentrations (6, 10 microM). Similarly, the responses to low doses of dilazep were reduced after desensitization of the organ to adenosine, whilst the responses to higher doses were unaffected by this procedure. In a Ca2+-free, high-K+ medium, dilazep (1-10 microM) caused a parallel shift to the right of the Ca2+-induced contractions of the guinea-pig taenia caeci. Adenosine showed only slight Ca2+-antagonistic properties within the mM range of concentrations. These findings suggest that, at the higher concentration tested, dilazep exhibits Ca2+-antagonistic properties unrelated to its adenosine-mediated mode of action.

Effects of dilazep on human platelets and rat vascular tissue: in vitro studies on platelet aggregation, and arachidonic acid oxidation

The "in vitro" effects of Dilazep on platelet aggregation and arachidonic acid oxidation in platelets and vessel wall were studied. Dilazep exerted a clearcut inhibitory effect on platelet aggregation induced by several stimuli. In addition, the compound completely suppressed malondialdehyde production by platelets elicited by collagen and thrombin, in a dose-dependent fashion. The evaluation of Dilazep effects on the in vitro release of prostacyclin-like material by rat aortic tissue did not provide any indication about an interference of the drug on the generation of endogenous antiaggregatory material.

Saturable, high affinity binding of the nucleoside transport inhibitor, nitrobenzylthioinosine, to guinea pig cardiac membranes

The site-specific binding of the potent nucleoside transport inhibitor, [3H]nitrobenzylthioinosine ([3H]NBMPR), to guinea pig cardiac membranes was rapid, reversible and saturable. [3H]NBMPR bound with high affinity to a single class of sites at which the KD was 0.23 +/- 0.07 nM and which had a Bmax of 1700 +/- 290 fmol/mg protein. Several recognized nucleoside transport inhibitors and benzodiazepines inhibited the binding of [3H]NBMPR with an order of potency similar to that observed for the inhibition of the binding of [3H]NBMPR to human erythrocytes and guinea pig synaptosomes.

Pharmacological observations of plasminogen activator release caused by vasoactive agents in isolated perfused pig ears

Influences of vasoactive agents on plasminogen activator release (PA release) and perfusion pressure (PP) were studied in isolated perfused pig ears. The pig ear was perfused with oxygenated Tyrode's solution, pH 7.4, at 37 degrees C via the main artery and the perfusate from the veins was collected at 2-min intervals. The drug was injected into a rubber tube connected in the front of arterial cannula, and the fibrinolytic activity in the collected perfusate was measured by the fibrin plate method. Acetylcholine, bradykinin, and histamine enhanced PA release in a dose-dependent fashion (0.1-3.0 micrograms). Purified human thrombin also enhanced PA release in a dose-dependent fashion (1.5-12 U). In coronary vasodilators, dilazep caused a dose-dependent increase of PA release (10-100 micrograms) and dipyridamole caused a slight increase at a dose of 300 micrograms. However, nitroglycerin, papaverine, diltiazem, and trapidil did not exert any effects on PA release and neither did adenosine and ATP. Vasoconstricting agents, namely, epinephrine, norepinephrine, phenylephrine, and serotonin exerted hypertensive effects in a dose-dependent fashion (0.1-3.0 micrograms); however, they did not cause measurable increases of PA release. These results suggest that vasodilating substances may be essential for the enhancement of PA release from vascular bed.

A possible mechanism of vasoactive agents on plasminogen activator release in isolated perfused pig ears

The mechanism of vasoactive agents on plasminogen activator (PA) release was studied in isolated perfused pig ears. In the perfusion with atropine (3 microM)-containing Tyrode's solution, the enhancement of PA release caused by acetylcholine (1.0 micrograms) was completely inhibited; however, increases caused by other potentiators, namely, bradykinin (1.0 micrograms), histamine (1.0 micrograms), dilazep (30 micrograms), and thrombin (6 U) were not affected. In the case of mepyramine (10 microM), the increase of PA release caused by histamine (1.0 micrograms) was completely inhibited; and that caused by dilazep (30 micrograms) was partially inhibited, however, increases caused by acetylcholine, bradykinin, and thrombin were not influenced. Papaverine (30 microM) which could completely abolish the hypertensive effect of norepinephrine (1.0 micrograms) exerted a partial inhibition of the enhancement of PA release caused by dilazep; however, it did not affect those caused by other agents. Quinacrine (50 microM) and indomethacin (100 microM) did not have any effects on the enhancements of PA release caused by the five potentiators.

The inhibitory effect of dilazep on in vivo accumulation of platelets onto the damaged aorta in rabbit. II. Morphological analysis

The inhibitory effect of dilazep on platelet adhesion and aggregation onto the damaged aorta was morphologically investigated using an animal model of thrombosis in which polyethylene tubing was inserted into the rabbit aorta in order to injure the intima. Rabbits were divided into 2 groups, control and dilazep-treated groups. The aortas 60 minutes after insertion of tubing were examined by light, scanning and transmission electron microscopy. An amount of adhered and aggregated platelets onto the exposed subendothelial surface of the aorta in rabbits pretreated with dilazep 100 micrograms/kg was significantly less than in control rabbits. Fibrin formation was also sparse in the mural thrombi in dilazep-treated group compared to that in control group. The results show that dilazep has the definite inhibitory effect in early mural thrombogenesis following the endothelial denudation in rabbit.

Metabolism of adenosine and 2'-deoxy-adenosine by fetal mouse calvaria in culture

The metabolism of endogenous adenosine and 2-deoxy-adenosine was studied in cultures of fetal mouse calvaria. Adenosine deamination was the most important pathway of metabolism. This was blocked by erythro-2-(2-hydroxy-3-nonyl)adenine (1 microM). Albumin in the medium could not account for the deaminase activity. The disappearance of adenosine from the medium was not influenced by two inhibitors of adenosine transport, dipyridamole and dilazep, but was competitively inhibited by 2-deoxy-adenosine. During culture there was a net increase in adenosine and inosine, possibly originating from damaged cells.

Effects of dilazep on fibrinolytic system in animals. I. Enhancement of fibrinolytic activity by administered dilazep in ex vivo experiment

The effects of dilazep on blood fibrinolytic system were studied in ex vivo experiment. Fibrinolytic activity in plasma was determined by the fibrin plate method at designed times after the administration of dilazep in guinea pigs, rabbits and mongrel dogs. In guinea pigs, fibrinolytic activity of euglobulin (plasminogen activator level, 1.10+/-0.08 CU/ml in control animals) rose to 1.53+/-0.24, 1.92+/-0.13 and 2.35+/-0.15 CU/ml 2 h after the p.o. administration of 30, 100 and 300 mg/kg of dilazep, respectively. Plasminogen levels in euglobulin were unchanged, however, plasmin inhibitory activities were lowered following the increase of plasminogen activator levels. About 2-fold increase of plasminogen activator level was also observed in rabbits 60 min after the p.o. administration of 300 mg/kg dilazep and returned to the initial level (0.054 CU/ml) within 3 h after the administration. A rapid increase of plasminogen activator level was observed in a case of the i.v. administration of dilazep into rabbits and mongrel dogs. In in vitro experiment, dilazep added to whole blood or plasma of guinea pigs ranging 0.1 to 1000 microgram/ml did not reveal any effects on plasminogen activator level or plasmin inhibitory activity in plasma.

Effects of dilazep on fibrinolytic system in animals. II. Enhancing effect of dilazep on plasminogen activator release in the isolated perfused pig ear

The influence of drugs on the release of plasminogen activator was studied in the isolated perfused pig ear. The pig ear was perfused with oxygenated Tyrode's solution pH 7 . 4, at 37 degrees C via main artery and perfusate from the veins was collected at 2 min intervals. The drug was injected into a rubber tube connected in the front of arteria cannula, and the fibrinolytic activity of perfusate collected was measured by the fibrin plate method using plasminogen-containing bovine fibrinogen. Under the test condition, dilazep enhanced plasminogen activator release (PA release) in a dose-dependent fashion ranging 10 to 100 microgram, however, it did not affect the perfusion pressure. Hypotensors, namely acetylcholine (0.1-3 microgram), bradykinin (0.1-3 microgram) and histamine (0.1-3 microgram) enhanced also the PA release in a dose-dependent fashion with no effects on perfusion pressure. Vasoconstricting drugs, namely phenylephrine (0.3-10 microgram), norepinephrine (0.1-3 microgram) and serotonin (0.1-3 microgram) exerted hypertensive effects on perfusion pressure in a dose-dependent fashion, however, it did not cause the PA release.

The antilipolytic effect of endogenous and exogenous adenosine in canine adipose tissue in situ

The effects of adenosine, 2-Cl-adenosine, two adenosine uptake inhibitors (dipyridamole and dilazep) and the adenosine deaminase (ADA) inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) were studied on basal and stimulated lipolysis in subcutaneous adipose tissue. The basal lipolysis was unaffected by all agents. Lipolysis induced by nerve stimulation (4 Hz, 5 min) was dose-dependently antagonized (up to 100%) by close i.a. infusions of adenosine (1--40 microM in blood); if the nerve induced vasoconstriction was prevented by alpha-adrenoceptor-blockade. 2-Cl-adenosine was a more potent antilipolytic agent than adenosine. EHNA (3--10 microM in blood) did not inhibit stimulated lipolysis in vivo possibly because of the low ADA activity in fat cells. Dipyridamole (0.5--1.5 microM in blood) in combination with EHNA increased the venous plasma concentration of adenosine from 0.3 +/- 0.05 to 0.7 +/- 0.1 microM and enhanced the tissue concentration close to 3-fold. Lipolysis induced by nerve stimulation (4 Hz) was reduced by about 40% by dipyridamole + EHNA and that induced by close i.a. noradrenaline injection (20 nmol) by approximately 60%. It is concluded that adenosine is an antagonist of stimulated lipolysis in subcutaneous adipose tissue in situ in concentrations that are reached during prolonged sympathetic nerve stimulation.

Effect of dilazep on myocardial contractility following acute ischemia and reperfusion in isolated blood-perfused canine left ventricular muscle

Myocardial protection by dilazep HCl, an antianginal drug and a potent calcium antagonist, against myocardial damage following acute ischemia and reperfusion was studied with respect to myocardial contractility in isolated blood-perfused canine left ventricular muscle. Myocardial function was expressed by percent recovery rate of maximal net developed tension. 1) The coronary infusion of dilazep revealed significant myocardial protection during normothermic ischemic arrest of 45 min and reperfusion. 2) The intravenous administration of dilazep to the support dog and Young's infusion also showed significant myocardial protection during normothermic ischemic arrest of 45 min and reperfusion. Dilazep showed no persistent depression of myocardial contractility due to its calcium antagonistic effect during reperfusion. 3) The combination of intravenous administration of dilazep to the support dog, Young's infusion, and hypothermia showed significant myocardial protection during prolonged ischemia and reperfusion even in hypertrophied ventricle. These results demonstrate that dilazep provides effective myocardial protection during ischemic arrest and reperfusion by preventing abnormal calcium accumulation in myocardial cells during reperfusion. No persistent depression of myocardial contractility during reperfusion may support dilazep's clinical application as a myocardial protective agent in open-heart surgery.

Role of adenosine in adipose tissue circulation

The vasodilatory effect of adenosine and some related compounds were studied in subcutaneous adipose tissue in situ. The effects of three drugs that inhibit adenosine elimination; two adenosine uptake blockers, dipyridamole and dilazep, the adenosine deaminase inhibitor, EHNA, were also studied. Plasma levels of adenosine were simultaneously determined by HPLC. Adenosine was a potent vasodilator and 2- and 6-substituted analogues were even more potent. Tissue blood flow was linearly related to the venous plasma concentrations of adenosine. An elevation of adenosine in plasma from 0.25 to 0.5 Mu M enhanced blood flow by approximately 50%. A further increase to 1 mu M was associated with a doubling of adipose tissue blood flow. Adenosine also increased the vascular conductance and the capillary filtration coefficient, indicating that is is active on all sections of the vascular bed. Theophylline and caffeine (30- 100 mu M in arterial plasma) antagonized the vasodilatory effect of exogenous adenosine, abolished vasodilation due to EHNA+dipyridamole and reduced resting blood flow. The results suggest that adenosine plays a physiological role in regulating adipose tissue blood flow.

Theophylline interferes with the modulatory role of endogenous adenosine on cholinergic neurotransmission in guinea pig ileum

The ability of theophylline and other phosphodiesterase inhibitors to alter contractile responses to cholinergic nerve stimulation was investigated in isolated longitudinal muscle of the guinea pig ileum. Theophylline in low concentrations (10-100 microM), having no or little effect on measured phosphodiesterase activity, antagonized inhibitory effects of exogenous adenosine. In higher concentrations (0.1-10 mM), shown to be effective in inhibiting phosphodiesterase, theophylline as well as a "pure" cAMP phosphodiesterase inhibitor, ZK 62, 711, inhibited contractile responses. Dipyridamole and dilazep, inhibitors of adenosine inactivation, and also selective inhibitors of cAMP and cGMP phosphodiesterase, respectively, were found to enhance effects of exogenous adenosine and to cause a marked leftward shift to adenosine threshold dose. When dipyridamole and dilazep by themselves had inhibitory effects these could be antagonized by theophylline, suggesting an action through increased levels of endogenous adenosine. As a further indication of endogenous adenosine modulating neurotransmission low concentrations of theophylline enhanced responses to transmural stimulation. Endogenous purine concentrations in tissues and bath media were measured by HPLC. Because of tissue and microbial adenosine inactivation direct estimates of extracellular adenosine concentration could not be obtained. However, adenosine levels increased during transmural stimulation, and during inhibition of adenosine inactivation were sufficient, even in the bath medium, to interfere with the cholinergic neurotransmission.

[Effects of dilazep on cerebral blood flow under normal conditions and recirculation impairment after cerebral ischemia (author's transl)]

Regional cerebral blood flow (r-CBF) in anesthetized dogs was measured by the H2 clearance method. Cerebral ischemia was induced by permanent ligation of bilateral vertebral arteries (VA) and a 10 min occlusion of bilateral common carotid arteries (CCA). Under normal conditions, dilazep (100 and 300 micrograms/kg i.v.) increased r-CBF dose-dependently without affecting arterial PO2, PCO2 and pH. r-CBF was reduced by 40% during cerebral ischemia. Relative r-CBF rates, as compared with pre-ischemic rates, were 85%, 80%, 77% and 75% at 30, 60, 90 and 120 min after cerebral ischemia, respectively, indicating development of recirculation impairment. Dilazep (100 and 300 micrograms/kg i.v. 30 min before CCA occlusion) did not affect r-CBF reduction during the state of cerebral ischemia, whereas it prevented re-circulation impairment after cerebral ischemia. Papaverine (300 micrograms/kg i.v. 30 min before CCA occlusion) exerted similar effects. These results suggest that dilazep is a potentially effective drug for treating cerebrovascular disorders.

Potentiation by dilazep on the negative inotropic effect of adenosine on guinea-pig atria

1 Dilazep, a coronary dilator, has been reported to potentiate the negative inotropic and negative chronotropic responses of guinea-pig atria to adenosine. Studies were made on the mechanism of the potentiating action of dilazep with special reference to the degradation and uptake of adenosine. 2 The negative inotropic actions of adenosine and adenine nucleotides, such as ATP, ADP, AMP and cyclic AMP, on guinea-pig atria were selectively and dose-dependently augmented by dilazep at concentrations insufficient to produce any effect alone (0.01 to 1 microM). 3 Incubation of atrial tissue with 8.8 nM adenosine, containing 0.1 microCi of [3H]-adenosine, resulted in accumulation of [3H]-adenosine in the tissue; dilazep (0.01 to 1 microM) inhibited this accumulation. 4 Adenosine (10 microM to 10 mM) was degraded to inosine and hypoxanthine during incubation with atrial tissue; dilazep (0.1 to 10 microM) retarded the disappearance of adenosine and the formation of inosine and hypoxanthine. 5 These results suggest that dilazep potentiates the negative inotropic effect of adenosine on guinea-pig atria by preventing both its accumulation by atrial tissue and degradation by deaminase.

The effects of dilazep and SG 75 on cyclic nucleotides in the coronary artery

We examined the effects of new long acting coronary vasodilators (dilazep and SG 75) on cyclic nucleotides in the coronary artery and the myocardium at the maximum coronary blood flow. The cyclic AMP concentrations in the anterior descending coronary artery after the injection of saline (control), SG 75 (0.2 mg/Kg), and dilazep (0.1 mg/Kg) were 229 +/- 20 pmole/Gm, 249 +/- 21 pmole/Gm, and 320 +/- 21 pmol/Gm, respectively. A significant increase above control values was found in the dilazep treated group (p less than 0.02). The cyclic GMP concentrations in the coronary artery after the injection of saline, SG 75, and dilazep were 35.6 +/- 4.4 pmole/Gm, 40.4 +/- 3.3 pmole/Gm, 35.3 +/- 3.2 pmole/Gm, respectively. There were no significant differences between them. The cyclic AMP and cyclic GMP concentrations in the left ventricular muscle did not significantly increase after the administration of dilazep and SG 75. Our findings showed that the mechanism of coronary vasodilating action of dilazep might be associated with an increased cyclic AMP in the coronary artery.

Influence of hexobendine, dipyridamole, dilazep, lidoflazine, inosine and purine riboside on adenosine uptake by the isolated epithelium of guinea pig jejunum

The uptake of (14C)adenosine by isolated epithelium of guinea pig jejunum, administered on the blood side, was inhibited by hexobendine, dipyridamole, dilazep and lidoflazine. On the lumen side, however, weak inhibition was observed with lidoflazine only and no significant change was recorded with hexobendine, dipyridamole or dilazep. This difference was not altered when the degradation of hexobendine by the jejunal epithelium was blocked by physostigmine. When adenosine uptake was already reduced by purine riboside, further addition of hexobendine, dipyridamole, dilazep or lidoflazine caused divergent changes depending on the side of administration. Adenosine uptake was further diminished on the blood side, but raised towards control values on the lumen side. By contrast, inosine inhibited adenosine uptake on both sides of the epithleium. The results suggest that the mechanism of adenosine uptake is different on either side with respect to inhibition characteristics, corresponding to differences in morphology and function of the two sides of the intestinal epithelium.

Chronotropic effects of coronary vasodilators as assessed in the isolated, blood-perfused sino-atrial node preparation of the dog

Chronotropic effects of 6 coronary vasodilators, carbochromen, dilazep, diltiazem, dipyridamole, nifedipine and verapamil, were compared by close-arterial administration to the isolated, blood-perfused sino-atrial node preparation of the dog. All drugs produced a dose-related decrease in sinus rate, and the order of negative chronotropic potency determined on a weight basis was as follows: (formula: see text). Higher doses of these drugs except dipyridamole caused atrial standstill. The order of potency causing atrial standstill determined on a weight basis was as follows: (formula: see text). Dipyridamole in lower doses produced a negative chronotropic effect alone, but with higher doses a positive chronotropic effect preceded a negative one. Carbochromen in a wide range of doses produced a triphasic response consisting of initial brief positive, succeeding main negative and final gradually-developing slight positive components.

[Effects of adenosine compounds of the vascular bed and effects of dilazep, theophylline, and indomethacin on blood flow changes of the postocclusive renal vessels]

In anesthetized dogs, intrarenal arterial injections of adenosine (Ads) and adenosine 5' monophosphate (AMP) caused transient, vasoconstrictions, but those of adenosine 5' diphosphate (ADP) and adenosine 5' triphosphate (ATP) caused vasodilations. All of these agents produced marked vasodilations in the mesenteric and femoral vascular beds. An i.v. injection of dilazep (10--30 microng/kg) enhanced significnatly the effects of Ads and AMP at these three vascular beds, whereas this compound had no effects on results with ADP, ATP, norepinephrine and angiotensin. Administration of theophylline (10--30 mg/kg) given intravenously attenuated Ads and AMP actions, but had no effects on the other four agents. Renal vasoconstrictions induced by Ads. AMP, norepinephrine and angiotensin were followed by slight vasodilations which were abolished by indomethacin (2--5 mg/kg) given intravenously. Based on these findings postocclusive renal vascular responses were examined. The responses were divided into two phases. Phase1 was the initial decrease and phase2 was the successive gradual increase in renal blood flow (RBF). Phase 1 was significantly potentiated by dilazep, but inhibited by theophylline. Phase2 was abolished by indomethacin. These results indicate that the postocclusive renal vascular responses may be mediated through Ads and/or AMP and prostaglandins released from the kidney.

Cardiohemodynamic effects of SK&F 24260, D 600, diltiazem, dilazep, and trimetazidine in the dog

The cardiohemodynamic effects of a hypotensive agent, SK&F 24260, and coronary vasodilators, diltiazem, dilazep, and trimetazidine, and D 600 were studied in anesthetized open-chest dogs. The systemic blood pressure, cardiac output (pulmonary arterial flow), venous return (sum of the inferior and superior caval flow) right atrial pressure and heart rate were measured. All 5 drugs decreased the systemic blood pressure and heart rate and increased the right atrial pressure. The venous return and the cardiac output were reduced by higher doses of all the 5 drugs. However, SK&F 24260 in a wide range of doses greatly and diltiazem slightly but clearly increased the venous return and cardiac output. It appears that SK&F 24260 afects predominantly blood vessels whereas the other drugs affect rather the heart to produce a negative inotropic action.

Effects of some purine derivatives on the guinea-pig trachea and their interaction with drugs that block adenosine uptake

1 Adenosine, adenosine 5'-triphosphate (ATP), adenine, inosine and guanosine all caused concentration-dependent relaxations of guinea-pig tracheal smooth muscle in vitro. The relative potencies in descending order were: adenine greater than or equal to guanosine greater than inosine greater than or equal to adenosine greater than or equal to ATP. 2 Responses to the purine compounds were unaffected by propranolol (1 mug/ml). 3 The spasmolytic potencies of adenosine and ATP were greatly enhanced in the presence of the adenosine uptake blocking drugs dipyridamole, hexobendine or Dilazep, whereas responses to adenine were unaffected and those to inosine and guanosine were reduced. 4 The spasmolytic potencies of noradrenaline, aminophylline, prostaglandin E2 and glyceryl trinitrate were unaffected by dipyridamole, hexobendine and Dilazep. 5 It is suggested that an adenosine uptake process may exist in the trachea of the guinea-pig and that this process is inhibited by dipyridamole, hexobendine and Dilazep.

[Effects of 1, 4-bis-(3-(3, 4, 5-trimethoxy benzoyl oxy)-propyl) perhydro-1, 4-diazepine (dilazep) on the isolated smooth muscles]

The effects of a new coronary vasodilator (dilazep) on isolated intestine, taenia coli, trachea, vas deferens, uter, aorta and coronary arteries were investigated in rats, guinea pigs, rabbits and dogs. Dilazep showed relaxant effects on isolated smooth muscle in a concentration of 10(-5) 3 X 10(-4) M and non-competitive inhibition on contraction induced by agonists (pD'2: 4.405.05). In guinea pig taenia coli, dilazep had a relaxant effect on K-contracture. The effect was qualitatively similar to that of papaverine. In guinea pig taenia coli, dilazep showed a Ca++ antagonistic effect in a concentration as high as 3 X 10(-6)M. The potency was stronger than dipyridamole, NaNO2 and aminophylline and equalled that of papaverine and hexobendine. In guinea pig taenia coli, dilazip potentiated relaxant effects induced by adenosine and adenine nucleotides in a concentration as high as 10(-8)M. The potency was stronger than that of dipyridamole. From these results, it is suggested that the potentiating effect of both adenosine and adenine nucleotides and Ca++ antagonistic effect of dilazep may play an important role in producing the coronary vasodilating effect.