Effects of monatepil maleate, a new Ca2+ channel antagonist with alpha1-adrenoceptor antagonistic activity, on cholesterol absorption and catabolism in high cholesterol diet-fed rabbits.

The mechanism of the prophylactic effect against hyperlipidemia by monatepil maleate was investigated in animal models. Monatepil maleate is an antihypertensive agent with Ca2+-channel antagonistic, alpha1-adrenergic receptor-blocking, and lipid peroxidation inhibitory activity. In high cholesterol diet-fed rabbits, monatepil maleate (30 mg/kg, p.o., once daily for 9 weeks) showed a prophylactic effect against increases in total cholesterol and beta-lipoprotein. Monatepil maleate significantly accelerated the clearance of radioactivity from the blood after intravenous injection of low-density lipoprotein (LDL) labeled with [1alpha,2alpha (n)-3H]cholesterol, increasing biliary excretion of [3H]-bile acids without modifying bile acid composition. Furthermore, monatepil maleate tended to inhibit the absorption of orally administered [1alpha,2alpha (n)-3H]cholesterol from the gastrointestinal tract in these rabbits. In Watanabe heritable hyperlipidemic (WHHL) rabbits, an animal model of hepatic LDL receptor deficiency, monatepil maleate (30 mg/kg, p.o., once daily for 6 months) did not suppress the increase in plasma lipids. These results suggest that the plasma lipid lowering effect of monatepil maleate requires the presence of hepatic LDL receptors. It is also suggested that monatepil maleate improves plasma lipid metabolism through two mechanisms: enhancement of clearance of plasma LDL, which may be mediated by up-regulation of hepatic LDL receptors, and acceleration of conversion of free cholesterol to bile acids in the liver.

Novel, highly potent aldose reductase inhibitors: (R)-(-)-2-(4-bromo-2-fluorobenzyl)-1,2,3,4- tetrahydropyrrolo[1,2-a]pyrazine -4-spiro-3'-pyrrolidine-1,2',3,5'-tetrone (AS-3201) and its congeners.

A series of novel tetrahydropyrrolo[1,2-a]pyrazine derivatives were synthesized and evaluated as aldose reductase inhibitors (ARIs) on the basis of their abilities to inhibit porcine lens aldose reductase (AR) in vitro and to inhibit sorbitol accumulation in the sciatic nerve of streptozotocin-induced diabetic rats in vivo. Of these compounds, spirosuccinimide-fused tetrahydropyrrolo[1, 2-a]pyrazine-1,3-dione derivatives showed significantly potent AR inhibitory activity. In the in vivo activity of these derivatives, 2-(4-bromo-2-fluorobenzyl)-1,2,3,4-tetrahydropyrrolo[1, 2-a]pyrazine-4-spiro-3'-pyrrolidine-1,2',3,5'-tetrone (23t) (SX-3030) showed the best oral activity. The enantiomers of 23t were synthesized, and the biological activities were evaluated. It was found that AR inhibitory activity resides in the (-)-enantiomer 43 (AS-3201), which was 10 times more potent in inhibition of the AR (IC50 = 1.5 x 10(-8) M) and 500 times more potent in the in vivo activity (ED50 = 0.18 mg/kg/day for 5 days) than the corresponding (+)-enantiomer 44 (SX-3202). From these results, AS-3201 was selected as the candidate for clinical development. The absolute configuration of AS-3201 was also established to be (R)-form by single-crystal X-ray analysis. In this article we report the preparation and structure-activity relationship (SAR) of tetrahydropyrrolopyrazine derivatives including a novel ARI, AS-3201.

Inhibitory effect of monatepil maleate on acyl-CoA:cholesterol acyltransferase activity in the liver of cholesterol-fed Japanese monkeys.

We have previously demonstrated that monatepil maleate, AJ-2615, a new calcium antagonist endowed with alpha1-adrenoceptor blocking property, has antiatherosclerotic and plasma lipid-lowering effects in Japanese monkeys fed on a cholesterol-rich diet. To clarify the mechanisms on plasma lipid-lowering action, we investigated the effect of monatepil maleate in these monkeys on hepatic acyl-CoA:cholesterol acyltransferase (ACAT) activity. Both ACAT activity and esterified cholesterol content in the livers of monkeys fed on a cholesterol-rich diet for 6 months significantly increased about 7- and 16-fold, respectively, as compared with those in monkeys fed on a standard diet. Monatepil maleate (30 mg/kg/day for 6 months, orally) inhibited the increases of ACAT activity and esterified cholesterol content by 51% and 71%, respectively. In in vitro experiments, monatepil maleate inhibited ACAT activity in a concentration-dependent manner, whereas it did not affect 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity. A kinetic analysis revealed that monatepil maleate was a noncompetitive type inhibitor of ACAT. Hepatic ACAT activity was significantly correlated to hepatic esterified cholesterol content (r = 0.775, P < .0001), to plasma very low density lipoprotein (VLDL) content (r = 0.765, P < .0001) and to plasma total cholesterol content (r = 0.573, P < .005) in the monkeys. These results suggest that ACAT-inhibiting effect of monatepil maleate plays an important role in the reduction of hyperlipidemia.

Post-treatment of transient focal cerebral ischemia in rats with the novel cerebrovascular-selective Ca2+ channel antagonist (+/-)-(E)-1-(3-fluoro-6,11-dihydrodibenz[b,e]-oxepine-11-yl)-4-(3-pheny l-2-propenyl)-piperazine dimaleate.

The efficacy of post-ischemic treatment with AJ-3941 ((+/-)-(E)-1-(3-fluoro-6,11-dihydrodibenz[b,e]-oxepine-11-yl )-4-(3-phenyl-2- propenyl)-piperazine dimaleate, CAS 143110-70-7), a cerebrovascular selective Ca2+ channel antagonist, on brain infarction induced by focal ischemia-reperfusion in rats was evaluated. Focal ischemia was induced by transient occlusion of middle cerebral artery (MCA) with a 3-0 nylon monofilament for 90 min. One day after MCA occlusion (MCAo), brain infarct size was determined by measuring 2,3,5-triphenyltetrazonium chloride-negative stained area of the serial brain sections. The development of cerebral infarction was observed in both regions of cortex and subcortex, such as striatum, caudatum, putamen, hippocampus and corpus callosum. Post-ischemic treatment with AJ-3941 (1 or 3 mg/kg p.o., 10 min and 3 h after the occlusion) significantly reduced the infarct size and volume in the ipsilateral hemisphere in a dose-dependent manner, compared to the solvent control. The reducing effect was observed mainly in the cortical region, and a significant reduction of the subcortical infarct volume was found at the higher dose (3 mg/kg). Post-ischemic treatment with the thromboxane A2 synthetase inhibitor, sodium ozagrel (150 micrograms/kg/min i.v. infusion, between 1 h and 24 h after the MCAo) did not reduce the infarct volume in the hemisphere after ischemia-reperfusion. AJ-3941 had only minimum effect on the elevation of body temperature during ischemia-reperfusion. These results indicate that post-ischemic treatment with AJ-3941 may ameliorate the brain injury after the transient focal cerebral ischemia, and they suggest that AJ-3941 has beneficial effects for treatment of ischemic cerebral damage, such as stroke.

Cerebrovascular selectivity and vasospasmolytic action of the novel calcium antagonist (+/-)-(E)-1-(3-fluoro-6, 11-dihydrodibenz[b,e]oxepin-11-yl)-4-(3-phenyl-2-propenyl)-piperazine dimaleate in isolated cerebral arteries of the rabbit and dog.

The cerebrovascular selectivity and vasospasmolytic action of AJ-3941 ((+/-)-(E)-1-(3-fluoro-6, 11-dihydrodibenz[b,e]oxepin-11-yl)-4-(3-phenyl-2-propenyl)-p iperazine dimaleate. CAS 143110-70-7), a new calcium antagonist, were studied in isolated rabbit and dog arterial preparations. In rabbit arterial ring preparations, AJ-3941 dose-dependently inhibited the contractions of various arteries caused by high K(+)-depolarization (high K+) and prostaglandin F2 alpha (PG). The inhibitory potency of AJ-3941 varied in different arteries, in descending order as follows: high K+: basilar > coronary > femoral > renal > mesenteric artery, PG: basilar > coronary > > femoral and renal artery. The median inhibitory concentration (IC50) in the basilar artery was over 40 times lower than that in the mesenteric or femoral artery for which the weakest inhibition in the examined arteries was observed. This selective action of AJ-3941 for cerebral artery was also observed in the frontal and middle cerebral arteries of dogs. The selectivity for the rabbit basilar artery was higher than those of flunarizine and nicardipine. Additionally, the contractile response of the rabbit basilar artery induced by phorbol 12,13-dibutyrate (PDBu), an activator of protein kinase C (PKC), was greater than those of the arteries examined such as the coronary, femoral and mesenteric arteries. The response in the basilar artery was greatly reduced in Ca(2+)-free medium, while this was not the case in other arteries. AJ-3941 as well as H-7, an inhibitor of PKC, potently inhibited PDBu-induced contractile response in the basilar artery in the presence, but not in the absence of Ca2+ in the medium, whereas the existing calcium antagonists, diltiazem and nicardipine, did not inhibit the contractile response in both conditions. These results suggest that the PKC-dependent system which is mediated by influx of extracellular Ca2+ profoundly contributes to the contraction of the cerebral artery and that the cerebroselective-vasodilating effect of AJ-3941 may depend, at least partly, on the inhibition of the PKC-mediated contractile response. In rabbit basilar arteries, AJ-3941 caused a dose-dependent inhibition of the contraction induced by various vasospasmogens, such as endothelin-1 (ET), arachidonic acid, 15-hydroperoxy-eicosatetraenoic acid and the thromboxane A2-mimetic U-46619. Furthermore, when isolated basilar arteries of the dog were perfused intraluminally with AJ-3941 at the concentration that inhibits high K(+)- or PG-induced contraction in the rabbit basilar artery, AJ-3941 effectively antagonized the vasospasm induced by extraluminal application of PG or ET. However, when flunarizine, nicardipine, diltiazem or verapamil was used for intraluminal perfusion of the same preparations, none of these drugs exerted spasmolytic effect. These results indicate that AJ-3941 has cerebrovascular selective-vasospasmolytic action, and consequently is thought to be effective in cerebrovascular disorder such as vasospasm following subarachnoid hemorrhage.

Alacepril, an angiotensin-converting enzyme inhibitor, prevents cerebral vasospasm in subarachnoid hemorrhage model in rats.

The effects of angiotensin-converting enzyme (ACE) inhibitors was investigated on the development of cerebral vasospasm and on the endothelium-dependent relaxation in the rat subarachnoid hemorrhage (SAH) model. Alacepril or enalapril was used as an ACE inhibitor with or without a thiol moiety in the structure. SAH rats or sham-operated rats were produced by the injection of homologous blood or artificial cerebrospinal fluid into the cisternal magna, respectively. In the SAH rat, cerebral vasospasm was observed at 24 h after blood injection. Acetylcholine (Ach)-induced relaxation in basilar arteries from SAH rats significantly decreased compared to that from sham-operated rats, although the relaxation induced by 3-morpholinosydnonimine, sodium nitroprusside or papaverine did not decrease. These results suggest that the endothelium cell function of basilar arteries in SAH rats is damaged. Alacepril prevented both the development of cerebral vasospasm and the suppression in the Ach-induced relaxation of basilar artery in SAH rats. However, enalapril did not prevent the suppression of Ach-induced relaxation in SAH rats, despite the tendency to prevent cerebral vasospasm. Therefore, it is suggested that the preventive effect of alacepril on cerebral vasospasm could be based on its protective effect on endothelium-dependent relaxation system.

Protective effect of zonisamide, an antiepileptic drug, against transient focal cerebral ischemia with middle cerebral artery occlusion-reperfusion in rats.

PURPOSE: The antiepileptic effects of zonisamide (ZNS) have been well documented experimentally and clinically. The purpose of this study was to examine whether ZNS reduces cerebral damage after transient focal ischemia in rats. METHODS: Ischemia was induced by a transient occlusion of the left middle cerebral artery (MCA) with a 3-0 nylon monofilament for 90 min. Neurological evaluation was performed by measuring the event of neurological deficit of the contralateral forepaw and hindpaw at 10 min and 1 day after MCA occlusion (MCAo). Brain infarct size was determined by measuring triphenyltetrazonium chloride-negative stained area of the serial brain sections 1 day after MCAo. RESULTS: The pre- or postischemic treatment with ZNS [(10-100 mg/kg p.o.), 30 min before and 4 h after or 15 min and 4 h after the occlusion] markedly reduced cerebral damage in the ipsilateral hemisphere and the neurological deficit induced by transient ischemia. The reducing effect on the damage was observed in the cortical and subcortical regions. Preischemic treatment with carbamazepine (CBZ 60 mg/kg p.o. twice 30 min before and 4 h after MCAo) tended to reduce the cerebral damage and neurological deficit, but the lower dose (20 mg/kg p.o. twice) did not. Valproate (VPA 1,000 mg/kg p.o. twice) also had no effect. CONCLUSIONS: ZNS at the anticonvulsant dose, unlike CBZ and VPA, ameliorated the brain infarction and the event of neurological deficit after transient focal cerebral ischemia. These data suggest that ZNS has therapeutic potential in protecting against ischemic cerebral damage, such as stroke.

Prevention by the new Ca2+ channel antagonist, AJ-3941, of loss of endothelium-dependent relaxation after subarachnoid hemorrhage in rats.

AJ-3941 ((+/-)-(E)-1-(3-fluoro-6,11-dihydrodibenz[b,e]-oxepine-11-yl ) -4-(3-phenyl-2-propenyl)-piperazine dimaleate; CAS No. 143110-70-7), a cerebrovascular-selective Ca2+ channel antagonist having anti-lipid peroxidative action, was reported to prevent cerebral vasospasm following subarachnoid hemorrhage in rats. The present study was undertaken to determine whether AJ-3941 protects the impairment of cerebroarterial endothelium-dependent relaxation which is concomitantly induced with cerebral vasospasm. Subarachnoid hemorrhage biphasically suppressed the response to acetylcholine in rat basilar artery, at 0.5 h (n = 4; P < 0.06) and 1 day (n = 5; P < 0.05) after subarachnoid hemorrhage. The reduction of the responses was correlated significantly to the degree of vasospasm determined angiographically. This reduction was accompanied by a 49% increase of arterial lipid peroxide contents. Endothelium-independent relaxation in subarachnoid hemorrhage rats was preserved in response to 3-morpholinosydnonimine, sodium nitroprusside and papaverine. AJ-3941 prevented (n = 6-8, P < 0.05) the suppression of the acetylcholine-induced response and the increase in lipid peroxide content in subarachnoid hemorrhage rats. These results suggest that AJ-3941 could exert its vasospasmolytic effect by preserving endothelial function through its anti-lipid peroxidative action, in addition to its inhibition of vasospasmogen-induced vasoconstriction related to intracellular Ca2+ mobilization.

Effect of (+/-)-(E)-1-(3-fluoro-6,11-dihydrodibenz[b,e]-oxepine-11 -yl)-4-(3-phenyl-2-propenyl)-piperazine dimaleate on cerebral vasospasm and impairment of cerebral circulation in subarachnoid hemorrhage model in rats.

A subarachnoid hemorrhage (SAH) model in rats was produced by the injection of homologous blood into the cisterna magna. Effects of AJ-3941 ((+/-)-(E)-1-(3-fluoro-6,11 -dihydrodibenz[b,e]-oxepine-11-yl)-4-(3-phenyl-2-propenyl)-p iperazine dimaleate, CAS 143110-70-7) on the development of cerebral vasospasm and the change of regional cerebral blood flow (rCBF) following SAH was investigated in this model. Cerebral vasospasm following SAH showed a biphasic pattern with an early phrase at 10 min and a late phrase on 1 day after blood injection. The physiological parameters (blood pressure, heart rate and blood gas contents) remained stable within the physiological range throughout the course of the experiment. AJ-3941 (0.01 mg/kg i.v. or 0.3 mg/kg p.o.) significantly prevented the development of late phase cerebral vasospasm. Cisternal injection of homologous blood significantly reduced rCBF immediately after the injection and the reduction lasted during the observation period (30 min). Reduction in rCBF after the injection of homologous blood was prevented by AJ-3941 (0.01 mg/kg i.v.). rCBF in AJ-3941-treated rats completely returned to the basal values after 30 min. The present suggest that AJ-3941 may be useful in the prevention of late spasm and in the improvement of cerebral circulation impaired with SAH.

Protective effect of the novel cerebrovascular-selective calcium antagonist (+/-)-(E)-1-(3-fluoro-6, 11-dihydrodibenz[b,e]-oxepine-11-yl)-4-(3-phenyl-2-propenyl)-piperazine dimaleate on ischemic brain damage after permanent middle cerebral artery occlusion in rats.

In this study the effect of post-ischemic treatment of AJ-3941 ((+/-)-(E)-1-(3-fluoro-6,11-dihydrodibenz [b,e]-oxepine-11-yl)-4-(3-phenyl-2-propenyl)-piperazine dimaleate, CAS 143110-70-7) a cerebrovascular-selective calcium antagonist, on brain infarction and edema in a rat model of focal cerebral ischemia with permanent middle cerebral artery occlusion (MCAo) was evaluated. Brain infarct size was determined at 24 h after MCAo by measuring 2,3,5-triphenyltetrazolium chloride-negative stained area of the serial brain sections. Post-ischemic treatment of AJ-3941 (3 mg/kg p.o.), 10 min and 3 h after the insult, significantly reduced brain infarct size by 44-80%, compared to vehicle control. The reducing effect was observed both in the cortical and subcortical regions. Three days after MCAo, contents of water and Na+ in the ipsilateral hemisphere significantly increased comparing with those in control rats. Post-ischemic treatment with AJ-3941 (3 and 10 mg/kg twice daily p.o. for 2 days) markedly inhibited the increase in water content and suppressed the increase in Na+ content. In the contralateral hemisphere, these contents showed no significant differences between vehicle-treated group and either control (non-operated) or AJ-3941-treated group. AJ-3941 had only minimum effect on body temperature and physiological parameters, such as blood pressure, blood gases and glucose, even when the maximum dose used (10 mg/kg) was repeatedly administered. These results indicate that post-ischemic treatment with AJ-3941 may ameliorate the brain infarction and edema after permanent focal cerebral ischemia, and they also suggest that AJ-3941 has a beneficial effect in the treatment of ischemic cerebral damage.

Novel fluoroprostacyclin analogs with modified cycloalkylenyl chains. Highly potent and orally active anti-anginal agents.

Novel fluoroprostacyclin analogs (1a-f) have been synthesized and pharmacologically evaluated. Compounds 1a-c given intravenously or orally showed potent and long-lasting anti-anginal activities in an animal model.

Pharmacologic properties of a novel Ca2+ entry blocker, AJ-2615, in vitro.

We studied the in vitro vascular relaxant properties of AJ-2615, (+/-)-N-[6,11-dihydrodibenzo[b,e]-thiepin-11-yl]-4-[4- fluorophenyl]-1-piperazinebutanamide monomaleate, a novel compound with long-lasting antihypertensive activity. AJ-2615 inhibited the high K(+)-induced contractile response in rat aorta with an IC50 of 2.08 x 10(-8) M. It was 13 times less potent than nifedipine and 3, 10, and 15 times more potent than verapamil, diltiazem, and fluanarizine, respectively. AJ-2615 also inhibited the high K(+)-induced 45Ca influx in rat aorta at almost the same concentration as that for inhibition of the contractile response. The inhibition of 45Ca influx was reversed by Bay k 8644, a Ca2+ channel agonist. The effects of AJ-2615 on the contractile response and Ca2+ influx persisted for at least 120 min after AJ-2615 was removed from the medium. These results indicate that AJ-2615 acts directly on the potential-dependent Ca2+ channel in a long-lasting manner. AJ-2615 inhibited [3H]prazosin binding to dog aortic membranes (IC50 = 1.25 x 10(-8) M) and phenylephrine-induced contractile response in superior mesenteric artery (SMA) of rabbits (IC50 = 3.87 x 10(-8) M), indicating that AJ-2615 has potent alpha 1-adrenoceptor blocking activity. AJ-2615 at 10(-6) M did not inhibit the caffeine-induced contractile response in rabbit SMA in Ca(2+)-free medium, nor did it inhibit calmodulin (CAM) activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-platelet and anti-thrombotic effects of OP-41483.alpha-CD, a prostacyclin analogue, in experimental animals.

The effects of OP-41483.alpha-CD, 5(E)-6,9-deoxa-6,9 alpha-methylene-15-cyclopentyl-16,17,18,19,20-pentanor prostacyclin (PGI2).alpha-cyclodextrin clathrate, on platelet function and experimental thrombosis were studied. In human platelets, OP-41483 inhibited aggregation induced by adenosine diphosphate (ADP) or collagen, promoted disaggregation, and elevated cyclic adenosine monophosphate (cAMP) levels in vitro at the same order of concentrations. The equipotent antiaggregatory activity of OP-41483 to human platelets was observed in monkey platelets in vitro. Furthermore, intravenous administration of OP-41483 to monkeys, unlike PGI2, showed the antiaggregatory effect on platelets but with less effect on blood pressure, suggesting that a differential sensitivity to OP-41483 between platelet function and vascular tone exists in monkeys. In rabbits, OP-41483.alpha-CD attenuated platelet aggregation induced by ADP, collagen and platelet activating factor (PAF), decreased circulating platelet aggregates, and inhibited platelet adhesiveness to de-endothelialized blood vessels. These results suggest that the anti-thrombotic effects of OP-41483 are associated with its potent antiplatelet activities mainly because of the elevation of cAMP levels in the platelets. The potent anti-thrombotic and less hypotensive effects of this compound may be useful for various thrombotic disorders.

Effect of OP-41483.alpha-CD, a prostacyclin analog, on a clamp-induced endothelial injury in rats.

We studied the effect of OP-41483.alpha-CD, a stable prostacyclin analog, on clamp-induced endothelial injury in rats. The injury was assessed by vascular Evans blue leakage and using a scanning electron microscope. OP-41483.alpha-CD significantly reduced the Evans blue leakage at doses of 30 and 100 ng/kg/min. PGE1.CD was also found to show an equipotent inhibitory action on the dye leakage. From scanning electron microscopic observations, a moderate degree of intimal defects, microvillous projections and platelet adhesions at the luminal surface were seen in the specimens from OP-41483.alpha-CD (30 and 100 ng/kg/min) treated rats. Furthermore, OP-41483.alpha-CD, PGE1.CD and Dibutyryl cyclic AMP (DbcAMP) were found to accelerate a proliferation of cultured bovine endothelial cells in a dose-dependent manner in vitro. Taken together, these data indicate that the endothelial regenerative effect of OP-41483.alpha-CD could contribute to healing of clamp-induced endothelial injury and it may be an important therapeutic drug to protect vascular intimal injury.

Effects of OP-41483.alpha-CD, a stable prostacyclin analog, on cultured endothelial cell dysfunction caused by 15(S)-hydroperoxy-5,8,11,13-eicosatetraenoic acid (15-HPETE) in vitro.

We studied the effect of OP-41483.alpha-CD, a stable prostacyclin analog, on, 15-HPETE induced bovine endothelial cell dysfunction, which was assessed by measuring a number of endothelial cells attached to plastic plates. 15-HPETE decreased the number of attached endothelial cells in a concentration- and time-dependent manner. OP-41483.alpha-CD and PGI2 significantly inhibited 15-HPETE induced dysfunction of the cells at a concentration of more than 10(-9)M. Besides, DDA (10(-6) - 10(-4)M) an adenylate cyclase inhibitor, diminished the inhibitory effect of OP-41483.alpha-CD on 15-HPETE induced cell dysfunction in a concentration-dependent manner. Furthermore, OP-41483.alpha-CD increased cAMP levels in the endothelial cells in the range of 10(-10) to 10(-8)M in a dose-dependent manner. These data suggest that OP-41483.alpha-CD could exert an inhibitory action on 15-HPETE induced endothelial cell dysfunction via partly increasing its effect on the intracellular cAMP level.

Inhibitory effect of OP-41483.alpha-CD, a prostacyclin analog, on peripheral vascular lesion models in rats.

The effect of a chemically stable prostacyclin analog, OP-41483 alpha-cyclodextrin clathrate (OP-41483.alpha-CD), on vascular lesions, platelet aggregation and blood pressure were examined and compared with those of prostaglandin E1 alpha-cyclodextrin clathrate (PGE1.CD) in in vivo rat models. 1) In the laurate (1 mg/leg, i.a.)-induced arterial thrombotic model, OP-41483.alpha-CD (1 microgram/kg/min, i.v.) prevented the progression of femoral arterial vascular lesions and enhanced the development of collaterals in the femoral artery. PGE1.CD did not inhibit the progression of vascular damages. 2) In the model of vasoconstriction induced by epinephrine (0.05 mg/tail, s.c.) and ergotamine (2 mg/kg, s.c.), OP-41483.alpha-CD and PGE1.CD, at 1 microgram/kg/min, inhibited the progress of of tail gangrene and lessened the decrease in tail cutaneous blood flow. 3) OP-41483.alpha-CD (1 microgram/kg/min) suppressed the ADP (0.1 mg/kg/min, i.v.)-induced decrease in the number of circulating platelets without affecting the change in blood pressure. In contrast, PGE1.CD (3 micrograms/kg/min) inhibited ADP-induced thrombocytopenia with a decrease in blood pressure. These results indicate that OP-41483.alpha-CD has antiplatelet and cutaneous blood flow improving activities that are greater than its hypotensive effect and may be of therapeutic potential in peripheral vascular diseases.

Studies on antiplatelet effects of OP-41483, a prostaglandin I2 analog, in experimental animals. II. Mechanism of its antiplatelet effect.

The mechanism for the inhibition of platelet functions by a prostaglandin I2 analog, OP-41483, was studied with guinea pig platelets. OP-41483, and PGI2 as well, inhibited aggregation, ADP release and thromboxane formation of platelets with IC50 values of 4.3-5.8 ng/ml and 0.6-0.9 ng/ml, respectively. The ligand binding study using [3H]-OP-41483 suggested that OP-41483 bound with different affinities to two classes of binding sites on platelets. The dissociation constant of OP-41483 for the higher affinity site corresponded to the IC50 values of its antiplatelet effect. PGI2 as well as OP-41483 displaced [3H]-OP-41483 previously bound to platelets, thus indicating that both agents exerted their antiplatelet effects by binding to the same site on platelets. OP-41483 and PGI2 activated adenylate cyclase and raised cyclic AMP levels in platelets. However, their inhibitory effect on platelet aggregation was not fully antagonized by an adenylate cyclase inhibitor, 2',5'-dideoxyadenosine (DDA), at a concentration completely inhibiting the increase of cyclic AMP. Moreover, this DDA-resistant effect of OP-41483 disappeared in the presence of calcium chloride (10(-4)-10(-3) M). OP-41483 and PGI2 inhibited thrombin-induced Ca++ influx into platelets. The inhibition of Ca++ influx was not reversed by DDA. Based on these results, we speculate that the inhibitory effects of OP-41483 and PGI2 on platelet functions are produced through dual mechanisms: one mediated by activation of adenylate cyclase and the other by an inhibition of Ca++ influx; and these two mechanisms seem to be independent of each other.

General pharmacology of recombinant human tumor necrosis factor. 1st communication: effects on cardiovascular, gastrointestinal, renal and blood functions.

The effects of recombinant human Tumor Necrosis Factor (rHu-TNF, PT-050), an antitumor agent, on the cardiovascular, gastrointestinal, renal and blood functions were examined in experimental animals. 1. PT-050 at 10(5) U/kg i.v. did not affect blood pressure and blood flow in anesthetized dogs. However, these were decreased 2-3 h after i.v. injection of 10(6) U/kg. A sustained decrease in blood pressure was seen in conscious dogs. PT-050 decreased systolic blood pressure and increased heart rate with a peak at 5-7 h after administration of 10 micrograms/kg (2.55 x 10(4) U/kg) i.v. and 10(5) U/kg s.c. PT-050 was without effect on perfusion volume in rabbit ear vessel preparations. 2. PT-050 enhanced gastric emptying in rats and intestinal charcoal meal propulsion in mice at 10(6) and 10(7) U/kg s.c., respectively. It decreased gastric juice volume and acid content with an increase of gastric juice pH in pyrolus ligated rats at 10(6) U/kg s.c. 3. PT-050 caused diarrhea at 10(5) U/kg i.v. in mice, while at 10(7) U/kg s.c., it did not exert the effect. 4. PT-050 increased urine volume and Na+ excretion at 3 x 10(3) U/kg i.v. and 10(5) U/kg s.c. in saline-loaded rats. 5. PT-050 decreased platelet counts at 10(5) U/kg i.v., depressed platelet aggregation responses to collagen and ADP at 10(6) U/kg i.v., and prolonged APTT and PT at 3 x 10(5) U/kg i.v. in rats, although it neither affected platelet aggregation nor blood coagulation in vitro. PT-050 neither affected platelet counts at 10(5) U/kg s.c., nor platelet aggregation at 10(7) U/kg s.c.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on antiplatelet effect of OP-41483, a prostaglandin I2 analog, in experimental animals. I. Effect on platelet function and thrombosis.

Antiplatelet and antithrombotic effects of OP-41483, a PGl2 analog, were studied in experimental animals, and the following results were obtained: 1) With 10 min-intravenous infusion to guinea pigs, OP-41483 inhibited platelet adhesiveness and platelet aggregation at 300-1000 ng/kg/min and 1000 ng/kg/min, respectively. In these effects, OP-41483 was 1-3 times more potent than carbacyclin and 3 times less potent than PGl2. 2) With oral administration to guinea pigs, OP-41483 given as its alpha-cyclodextrin clathrate (OP-41483 alpha-CD) inhibited platelet adhesiveness at doses higher than 1.0 mg/kg (expressed in terms of OP-41483), whereas PGl2 and carbacyclin did not at 10 mg/kg. OP-41483 alpha-CD also inhibited platelet aggregation after a single dose of 3 mg/kg and repeated doses of 3 mg/kg/day for 7 days. 3) In the electrically induced thrombosis model of guinea pig mesenteric artery, OP-41483 (300-1000 ng/kg/min, i.v.-infusion) and OP-41483 alpha-CD (1.0-3.0 mg/kg, p.o.) inhibited thrombus formation, but heparin (1.0-10 U/kg/min, i.v.-infusion) did not. 4) In the rabbit extracorporeal circulation thrombosis model, OP-41483 (100 and 300 ng/kg/min, i.v.-infusion) inhibited thrombus formation in the extracorporeal shunt and prevented the decrease in platelet count, hematocrit and fibrinogen level in circulating blood. Heparin (1.0-3.0 U/kg/min, i.v.-infusion) also inhibited the thrombus formation and the decrease in fibrinogen level, but did not inhibit the decrease in hematocrit and platelet count.

General pharmacology of the novel antiepileptic compound zonisamide. 2nd communication: effects on cardiovascular, visceral, renal and blood functions.

The effects of 1,2-benzisoxazole-3-methanesulfonamide (zonisamide, AD-810, CI-912), an antiepileptic compound, on the cardiovascular, visceral, renal and blood functions were compared with those of carbamazepine and, in part, acetazolamide in experimental animals. 1. Zonisamide (30 mg/kg i.v.) transiently lowered the blood pressure and decreased the blood flows in the carotid and femoral arteries in anesthetized dogs. The effects were 3 times less potent than those of carbamazepine, Zonisamide, when orally administered, did not affect the blood pressure even at 300 mg/kg in conscious rats. 2. Zonisamide little affected the autonomic nervous system even at high doses. In anesthetized cats, contractions of the nictating membrane by electrical stimulation of the cervical sympathetic nerve, pressor responses to norepinephrine, and depressor responses to acetylcholine, all were not modified with zonisamide (100 mg/kg i.v.). In isolated guinea-pig ileum, contractions induced by acetylcholine, histamine and bradykinin were not affected by zonisamide up to a concentration of 10(-3) g/ml zonisamide, although those by serotonin and nicotine were depressed with high concentrations over 10(-5) g/ml. 3. With 100 mg/kg p.o., zonisamide decreased the gastric juice volume and pH in pylorus ligated rats, and depressed gastric emptying in rats, but did not inhibit the intestinal transit of charcoal meal in mice. These effects were less potent than those of carbamazepine. 4. Zonisamide increased the urine volume, pH, and Na+ and K+ concentrations in rats and anesthetized dogs. The renal blood flow and glomerular filtration rate were little changed with the high doses of zonisamide.(ABSTRACT TRUNCATED AT 250 WORDS)