The thromboxane A2/prostaglandin endoperoxide receptor antagonist activity of CV-4151, a thromboxane A2 synthetase inhibitor

The thromboxane A2/prostaglandin endoperoxide (TXA2/PGH2) receptor antagonist activity of CV-4151, a potent TXA2 synthetase inhibitor, was examined. CV-4151 inhibited guinea pig and human platelet aggregation induced by U-44069 with IC50 values of 1.2 +/- 0.3 X 10(-5) and 1.9 +/- 0.4 X 10(-5) M, respectively, and inhibited the specific binding of [3H]U-46619 to washed guinea pig and human platelets with IC50 values of 1.2 +/- 0.3 X 10(-6) and 5.1 +/- 1.0 X 10(-6) M, respectively. CV-4151 competitively inhibited the contraction of rabbit aortic strips induced by U-44069 with a pA2 value of 5.90. In experiments in mice in vivo, CV-4151 (1 and 10 mg/kg i.v.) significantly inhibited the thrombocytopenia induced by U-44069 in a dose-dependent manner. These results show that CV-4151 has a distinct TXA2/PGH2 receptor antagonist effect, and that this effect together with its inhibition of TXA2 synthetase could be important for the pharmacological action of this compound.     

Delay of the initiation of hypertension in spontaneously hypertensive rats by CV-4151, a specific thromboxane A2 synthetase inhibitor

When CV-4151, a specific thromboxane (TX) A2 synthetase inhibitor, was given orally to 4 week old (4w) spontaneously hypertensive rats (SHR) daily for 3 weeks, the initiation of hypertension was delayed by about one week. The agent increased urinary excretion of water, sodium and creatinine, reduced that of TXA2 (as TXB2), increased that of PGI2 (as 6-keto-PGF1 alpha) and enhanced urinary PGI2/TXA2. In 4w Wistar-Kyoto rats (WKY) and 18w SHR was established hypertension, the agent had little effect on blood pressure and renal function. In isolated, perfused kidneys of 6w SHR, CV-4151 markedly inhibited both arachidonic acid-induced pressor action and production of TXA2. TXA2 synthetase activity in renal cortical microsomes of 5w SHR was approximately 1.5 times higher than that in age-matched WKY. CV-4151 inhibited TXA2 synthetase activity of medullary and cortical microsomes more effectively in 5w SHR than in age-matched WKY. Thus, in young SHR, the TXA2 synthetase inhibitor seemed to improve renal function by altering the balance of renal TXA2 and PGI2 biosynthesis and subsequently caused a delay in the initiation of hypertension. The present findings lend support to the idea that an imbalance in the renal TXA2-PGI2 biosynthesis may be involved in the initiation of hypertension in SHR.     

CGS 12970: a novel, long acting thromboxane synthetase inhibitor.

CGS 12970 is a potent selective inhibitor of human platelet thromboxane synthetase in vitro (IC50 = 12 nM). It is four orders of magnitude less potent as an inhibitor of sheep seminal vesicle cyclooxygenase, bovine aorta prostacyclin synthetase and human leucocyte 15-lipoxygenase. The compound inhibited collagen-induced thromboxane B2 production by human platelets in vitro without an effect on the accompanying platelet aggregation induced by collagen, ADP, platelet activating factor, thrombin, arachidonic acid or the prostaglandin mimetic, U 46619. Administration of CGS 12970 to rats inhibited collagen-induced thromboxane B2 production but had no effect on platelet aggregation ex vivo. It also had no effect on platelet aggregation induced by thrombin or on plasma clotting times. A single oral dose of 1 or 3 mg kg-1 to rabbits inhibited thromboxane B2 production in clotting blood ex vivo for 12 or 24 h respectively. CGS 12970 inhibited thromboxane B2 production in vivo induced by intravenous administration of collagen to rats or calcium ionophore to guinea-pigs. In both cases there was a concomitant elevation of immunoreactive 6-keto-prostaglandin F1 alpha but no effect on the induced thrombocytopenia. As with other thromboxane synthetase inhibitors, CGS 12970 prolonged tail bleeding time in the rat. However, CGS 12970 was not as potent as other thromboxane synthetase inhibitors in this test. In addition to these usual effects of thromboxane synthetase inhibitors, CGS 12970 inhibited the thrombocytopenia induced by the Forssman reaction or ADP administration. In these tests the effect of the compound was of short duration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Myocardial salvage by a novel thromboxane A2 synthetase inhibitor in a canine coronary occlusion-reperfusion model

The effects of the new thromboxane A2 (TXA2) synthetase inhibitor sodium 6-(2-[1-(1H)-imidazolyl]methyl-4,5-dihydrobenzo[b]thiophene)carboxylate (RS-5186), 10 mg/kg i.v., on infarct size, polymorphonuclear leukocytes (PMNs) infiltration, gross myocardial hemorrhage and ventricular arrhythmias were studied using a canine coronary occlusion (2 h)-reperfusion (5 h) model. Infarct size (IS) and risk area (RA) were determined by a dual staining technique. 60 min before coronary occlusion dogs were randomly assigned to either the RS-5186 treated group (n = 11) or the control group (n = 15). RS-5186 reduced infarct size (RS-5186: 26.3 +/- 2.4% of RA (mean +/- SEM) vs control: 50.7 +/- 5.9%, p less than 0.01), and also reduced the area of gross myocardial hemorrhage (RS-5186: 3.9 +/- 2.6% of IS vs control: 22.4 +/- 4.0%, p less than 0.01). The drug also decreased the intensity of PMNs infiltration into the infarcted area (p less than 0.05). However, RS-5186 had no significant influence on the incidence of ventricular arrhythmias. These results suggest that the new thromboxane A2 synthetase inhibitor RS-5186 might be useful in salvaging ischemic myocardium.     

Effect of a novel thromboxane A2 synthetase inhibitor on ischemia-induced mitochondrial dysfunction in canine hearts

This study was designed to determine the effect of sodium 6-(2-[1-(1H)-imidazolyl]methyl-4,5-dihydrobenzo[b] thiophene)carboxylate (RS-5186), a new thromboxane A2 (TXA2) synthetase inhibitor, on mitochondrial function and lysosomal integrity in ischemic myocardium. 17 anesthetized mongrel dogs were divided into 2 groups. In the control group (n = 11), the left anterior descending arteries (LAD) of the dogs were occluded for 2 h and physiological saline was infused until the end of the experiment. In the RS-5186 treated group (n = 6), 25 min prior to LAD occlusion, RS-5186, 10 mg/kg, was injected for 10 min. 2 h after occlusion, mitochondria were prepared from both ischemic and non-ischemic areas, which were confirmed by Evans' blue dye, and mitochondrial function (respiratory control index: RCI, and the rate of oxygen consumption in state III respiration: St.III O2) was measured polarographically with succinate as substrate. Fractionation of myocardial tissue from both ischemic and non-ischemic areas was also performed, and the activities of lysosomal enzymes (N-acetyl-beta-glucosaminidase: NAG, beta-glucuronidase: beta-gluc) of each fraction were measured. 2-h LAD occlusion induced a significant greater decrease in mitochondrial function from the ischemic area of the control group (RCI: 2.80 +/- 0.45, St.III O2: 133.5 +/- 35.6 natoms/mg protein/min) compared with those from the non-ischemic area (RCI: 4.49 +/- 0.46, St.III O2: 344.0 +/- 31.9).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of thromboxane synthetase inhibitor on cerebral circulation and metabolism during experimental cerebral ischemia in spontaneously hypertensive rats

The protective effect of thromboxane synthetase inhibitor, OKY-046, on brain ischemia was studied in spontaneously hypertensive rats. Cerebral ischemia was developed by bilateral carotid artery ligation (BCL) for 1 or 3 h and thereafter, circulation was restored for 15 min. OKY-046, 5 or 30 mg/kg, or saline as control was administered i.v. before BCL. Neither blood pressure nor blood gases were altered by OKY-046 or saline injection. During BCL, cerebral cortical blood flow was reduced to 25 and 15% of the resting value at 30 and 60 min, respectively, and these changes were not different among the groups. In rats with ischemia longer than 1 h, the blood flow was well preserved by OKY-046, 30 mg/kg, to 10-17% of the resting level, thus significantly higher than that (less than 5%) in non-treated rats. After 15 min recirculation, the supratentorial lactate level was lower and adenosine triphosphate (ATP) was higher in OKY-046-treated rats than in the saline-treated ischemic rats. Plasma thromboxane B2 was increased markedly in 1 h ischemic-reperfused rats without treatment and the increase was almost completely inhibited by OKY-046. In contrast, 6-keto-prostaglandin F1 alpha was increased 8.5-fold after ischemia and the increase was not affected by the treatment. OKY-046 seems to have an antiischemic effect on acutely induced cerebral ischemia. Selective inhibition of thromboxane A2 production and an inversely high level of prostaglandin I2 may be an important contribution to protection of the microcirculation during ischemia and preservation of ischemic cerebral metabolism.     

A thromboxane A2 synthase inhibitor, DP-1904, prevents rat renal injury

The effects of DP-1904, a thromboxane (TX) A2 synthase inhibitor, on renal function were investigated by analysis of prostanoid metabolism in hydronephrotic and ischemic rat kidney models, and in isolated perfused normal and hydronephrotic rat kidneys. The increase in production of TXB2 in hydronephrotic or ischemic kidneys was significantly suppressed by intraperitoneal DP-1904 (10 mg/kg), with the 6-keto-prostaglandin F1 alpha to TXB2 ratio being significant increased. Urine volume, glomerular filtration rate and renal plasma flow were all improved. DP-1904 (0.3 micrograms/min) blocked the effects of infused arachidonic acid on isolated perfused normal rat kidneys thus reducing TXB2 levels and perfusion pressure but the pressor response to norepinephrine or angiotensin II remained unchanged. In isolated perfused hydronephrotic rat kidneys, DP-1904 suppressed the increase in perfusion pressure and TXB2 production caused by platelet-activating factor. These findings suggested that DP-1904 improved renal failure by specifically inhibiting TXA2 production.     

Irreversible inhibition of thromboxane (TX) A2 synthesis by Y-20811, a selective TX synthetase inhibitor.

As Y-20811, sodium (+-)-4-[alpha-hydroxy-5-(1-imidazolyl)-2-methylbenzyl]-3,5-dimethylb+ ++ enzoic acid, has been reported to inhibit serum thromboxane (TX) A2 production with a long duration of action, its mechanism of action was investigated. When [3H]Y-20811 (3 mg/kg) was administered orally to rats, the peak platelet concentration of Y-20811 was obtained 1 hr after the administration, and the T1/2 was 43 hr. The peak plasma concentration of Y-20811 was also obtained 1 hr after administration, but the elimination of Y-20811 from plasma was faster (T1/2 alpha = 1.5 hr, T1/2 beta = 15 hr) than that observed in platelets. Serum TXA2 (estimated as TXB2) production was inhibited significantly from 1 to 72 hr after the oral administration of unlabeled Y-20811 (3 mg/kg), which temporally resembled the change of the platelet Y-20811 concentration. In platelet-rich plasma, [3H]Y-20811 completely inhibited TXA2 production at about 1500 pg/10(9) platelets, and the IC50 level was about 600 pg/10(9) platelets, which was similar to values obtained in ex vivo studies. In addition, inhibition of TXA2 production by Y-20811 still remained after washing the drug-pretreated microsomes, whereas that of dazoxiben completely disappeared. A similar irreversible inhibition of TXA2 production was observed with aspirin. These results suggest that Y-20811 may firmly combine with platelet TX synthetase and may irreversibly inhibit TXA2 production.     

Thromboxane synthetase inhibitor UK38,485 lowers blood pressure in the adult spontaneously hypertensive rat

Treatment of young spontaneously hypertensive rats (SHR) with a thromboxane synthetase inhibitor (TSI) attenuates their subsequent development of hypertension. In this study, treatment of adult SHR during the established phase of hypertension with the TSI UK38,485 (100 mg/kg daily) lowered systolic blood pressure from baseline after 4 days of treatment to a maximum depression of 25 mm Hg on day 10 of the study. Additional confirmation of the fact that this TSI does not lower blood pressure acutely was made via continuous intraarterial recordings in SHR administered their first dose of UK38,485. Urinary dinor-6-keto-PGF1 alpha excretion was measured by a highly specific chemical-ionization, negative-ion GC/MS assay in the selective ion monitoring mode. This metabolite of PGI2 was not significantly affected by 6 days of daily administration of UK38,485 to adult SHR and implies that there was not sufficient endoperoxide shunting to affect total body PGI2 production. The finding that UK38,485 exhibited antihypertensive activity during established SHR hypertension was unexpected and has considerable practical and theoretical significance.     

Beneficial effect of OKY-046, a selective thromboxane A2 synthetase inhibitor, on experimental cerebral vasospasm

Effects of OKY-046, a selective inhibitor of thromboxane (TX)A2 synthetase and a platelet aggregation inhibitor, on in vitro and in vivo models of cerebral vasospasm were studied. The contraction of the isolated rabbit basilar artery by an exposure to 1.0 ml of whole rabbit blood plus 0.05 or 0.1 units/ml of thrombin was diminished by the treatment with 10(-4) M of OKY-046 and/or 10(-6) M of cinanserin. When the whole blood of rabbits treated intravenously with 1 mg/kg/min of OKY-046 was used, the contraction of the basilar artery was decreased to about half of the control contraction. Angiographically recognized cerebral vasospasm in vivo, by a transorbital injection of 5.0 to 7.0 ml of autologous arterial blood into the cisterna magna of dogs, was suppressed by 0.05 and 0.5 microgram of OKY-046. Moreover, the decrease in the regional cerebral blood flow in autologous blood infused-dogs was inhibited by 0.5 microgram of OKY-046. The increase in TXB2 in the cerebrospinal fluid of dogs was significantly inhibited, and the level of 6-keto-PGF1 alpha was slightly increased by the treatment of OKY-046. The ratio of 6-keto-PGF1 alpha/TXB2 was increased from 1.5 to 5.2 in OKY-046-treated dogs. No effect on the basal tone and response to vasoactive agonists such as norepinephrine, KCl and PGE1 was observed in the isolated spiral thoracic aorta of guinea pigs or rabbits. Taken together with our previous findings, we conclude that the inhibition of cerebral vasospasm in the in vitro and in vivo models by the treatment of OKY-046 might be due to an inhibition of platelet aggregation, an inhibition of TXA2 generation and an increase in the ratio of PGl2/TXA2.     

Effects of Y-20811, a thromboxane A2 synthetase inhibitor, on experimentally induced coronary thrombosis in anesthetized dogs.

The effects of Y-20811, a selective inhibitor of thromboxane A2 (TXA2) synthetase, on blood flow and local levels of immunoreactive thromboxane B2 (i-TXB2) and 6-keto prostaglandin F1 alpha (i-6-keto PGF1 alpha) in the coronary artery were investigated in the canine model of coronary thrombosis. Thrombosis was induced by applying an electric current to the intraluminal surface of the coronary artery. The plasma levels of i-TXB2 and i-6-keto PGF1 alpha were measured distal to the electrode. In the control group, coronary blood flow decreased and finally stopped 207 +/- 53 min (mean +/- S.E.M., n = 5) after the start of current application. The level of i-TXB2 rose before the coronary occlusion. Coronary blood flow did not change significantly in the Y-20811-treated group (1 mg/kg i.v.). The level of i-TXB2 decreased and remained significantly lower than that in the control group. The level of i-6-keto PGF1 alpha tended to increase slightly in the Y-20811-treated, but not in the control group. The weight of the thrombus in the Y-20811-treated group was significantly less than that in the control group (P less than 0.01). These results suggest that Y-20811 prevents coronary thrombosis by the inhibition of TXA2 production around the electrically injured lumen of the coronary artery.     

Oxygen-derived free radical-induced vasoconstriction by thromboxane A2 in aorta of the spontaneously hypertensive rat

This study was performed to clarify the mechanism of vasoconstriction induced by oxygen-derived free radicals in spontaneously hypertensive rats. The isometric tension of aortic rings from spontaneously hypertensive rats and Wistar-Kyoto rats was measured in Krebs-Henseleit solution. Oxygen-derived free radicals were generated by mixing xanthine and xanthine oxidase. The removal of endothelium enhanced the contractions induced by oxygen-derived free radicals. The inhibition of nitric oxide production with NG-nitro-L-arginine methyl ester (10(-4) M) enhanced the contractions. Treatment with the thromboxane A2 (TXA2) synthetase inhibitor OKY-046 (10(-4) M) or RS-5186 (10(-4) M) markedly reduced the contractions. Treatment with the cyclooxygenase inhibitor indomethacin (10(-5) M) and a TXA2/prostaglandin H2 (PGH2) receptor antagonist, ONO-3708 (10(-6) M), completely abolished the oxygen-derived free radical-induced contractions. In contrast, treatment with the PGI2 synthetase inhibitor tranylcypromine (10(-4) M) did not attenuate the oxygen-derived free radical-induced contractions. Whether endothelium was present or not, the release of TXB2, PGE2, and 6-keto-PGF1alpha, but not PGF2alpha, was increased by the production of oxygen-derived free radicals. Catalase and the hydroxyl radical scavenger deferoxamine plus mannitol markedly inhibited the oxygen-derived free radical-induced contractions. These results suggest that oxygen-derived free radical-induced vasoconstriction in spontaneously hypertensive rat aorta is caused by TXA2 and PGH2 released in smooth muscle.     

Effects of a pyridine derivative thromboxane synthetase inhibitor and its inactive isomer in endotoxic shock in the rat

1 We investigated the effects of a pyridine derivative thromboxane synthetase inhibitor and its inactive ortho isomer on arachidonic acid metabolism and pathophysiological sequelae of endotoxic shock. In vehicle-treated rats, 30 min after intravenous S. enteritidis endotoxin (15 mg/kg), plasma iTxB2 (the stable metabolite of thromboxane A2) increased from non-detectable levels (less than 100 pg/ml) to 763 +/- 250 pg/ml (n = 10). Plasma i6-keto-PGF1 alpha (the stable metabolite of prostacyclin, PGI2) increased to 1850 +/- 426 pg/ml, (n = 9) and plasma iPGE increased to 2350 = 560 (n = 5). Pretreatment with the pyridine active (PA) meta isomer (30 mg/kg i.p.) significantly (P less than 0.05) suppressed iTxB2 to 390 +/- 31 pg/ml (n = 10) although 6-keto-PGF1 alpha levels (1294 +/- 358 pg/ml, n = 5) and plasma iPGE (2847 +/- 1103 pg/ml, n = 5) were not significantly different from the shocked control values. In contrast, pretreatment with, the pyridine inactive (PI) ortho isomer did not significantly affect endotoxin-induced iTxB2 (1431 +/- 194 pg/ml, n = 5) or i6-keto-PGF1 alpha synthesis (628 +/- 266 pg/ml, n = 5). 2 Pretreatment of rats with the Tx synthetase inhibitor, PA, significantly enhanced (P less than 0.05) survival and prevented splanchnic infarction relative to both endotoxin shocked control rats and those pretreated with the PI isomer. 3 Significantly reduced lysosomal labilization, hepatocellular dysfunction and elevations in serum fibrin/fibrinogen degradation products were seen only in groups pretreated with the PA isomer. 4 The beneficial effects of the latter compound in endotoxic shock thus appear to be due to inhibition of Tx synthesis, since its ortho isomer did not inhibit TxA2 synthesis nor did it protect against endotoxic shock.     

Pharmacological characterization of cinnamophilin, a novel dual inhibitor of thromboxane synthase and thromboxane A2 receptor.

1. The pharmacological effects of cinnamophilin, a new lignan, isolated from Cinnamomum philippinense, was determined in vitro in human platelet, rat isolated aorta and guinea-pig isolated trachea and in vivo in mice and guinea-pigs. 2. Cinnamophilin inhibited dose-dependently human platelet-rich plasma (PRP) aggregation induced by arachidonic acid (AA), collagen and U-46619 with IC50 of 5.0 +/- 0.4, 5.6 +/- 0.6 and 3.0 +/- 0.4 microM, respectively. The second wave of ADP- or adrenaline-induced platelet aggregation was inhibited by cinnamophilin, while the first wave was only slightly inhibited by cinnamophilin above 30 microM. 3. Cinnamophilin was found to be a thromboxane A2 (TXA2) receptor blocking agent in human platelet, rat aorta and guinea-pig trachea as revealed by its competitive antagonism of U-46619-induced aggregation of human-PRP, contraction of rat aortic rings and guinea-pig tracheal rings with pA2 values of 7.3 +/- 0.2, 6.3 +/- 0.1 and 5.2 +/- 0.2, respectively. 4. [3H]-inositol monophosphate formation and the rise of intracellular Ca2+ caused by U-46619 in human platelet was suppressed by cinnamophilin (10 microM). 5. Cinnamophilin induced a dose-dependent inhibition of thromboxane B2 (TXB2) formation, while the prostaglandin E2 (PGE2) formation was increased. Cinnamophilin did not affect unstimulated platelet adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels. When the platelets were challenged with AA, a dose-dependent rise in cyclic AMP was observed. Dazoxiben (a pure TX synthase inhibitor) and SQ 29548 (a pure TXA2 receptor antagonist) did not affect cyclic AMP levels in AA-treated platelets.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of Y-20811, a specific thromboxane A2 synthetase inhibitor, on chemical mediator-induced bronchoconstriction in guinea pigs

We investigated the effects of Y-20811 on chemical mediator-induced bronchoconstriction and the release of chemical mediators into lung perfusion fluid during arachidonic acid (AA)-induced bronchoconstriction in guinea pigs. Y-20811 (0.01-1 mg/kg, i.v.), like acetylsalicylic acid or indomethacin, dose-dependently suppressed arachidonic acid- and LTD4-induced bronchoconstriction, and it (1 mg/kg, i.v.) also inhibited PAF-induced bronchoconstriction in guinea pigs. However, at a dose of 1 mg/kg, i.v., it was inactive against the bronchoconstriction induced by histamine, serotonin and acetylcholine in guinea pigs. Y-20811 (0.3-10 mg/kg) administered orally also prevented the LTD4-induced bronchoconstriction in a dose-dependent manner. This protective effect of Y-20811 (10 mg/kg, p.o.) persisted for at least 24 hr. Y-20811 (10 mg/kg, p.o.) also inhibited antigen-induced bronchoconstriction in guinea pigs passively sensitized with anti-ovalbumin guinea pig serum and pretreated with mepyramine. In the perfused and ventilated guinea pig lungs, Y-20811 inhibited AA-induced bronchoconstriction, decreased the release of TXA2 (estimated as TXB2) and increased the release of PGE2 into the perfused lung fluid, significantly (TXB2 and PGE2 were measured by HPLC). Therefore, Y-20811 suppressed various stimulant-induced bronchoconstrictions through the decrease of TXA2 production and the increase of PGE2 production. Thus, Y-20811 should prove useful as an anti-asthmatic drug.     

Effects of captopril on diabetic nephropathy in hypertensive women

Summary The effects of the angiotensin converting enzyme inhibitor captopril on blood pressure, proteinuria, creatinine clearance and metabolic control in diabetic nephropathy have been evaluated. Captopril 144 mg per day was given to 8 longstanding, insulin-dependent, diabetic females with nephropathy. The blood pressure was significantly reduced (systolic 45.4, diastolic pressure 30.6 and mean arterial pressure 33.8 mm Hg after 24 weeks of treatment).Plasma renin activity rose significantly from a basal value of 1.60 to 6.71 ng·ml^–1·h^–1, and so did serum potassium (from 4.57 to 4.83 mEq·l^–1).Serum aldosterone fell from 161 to 70.9 pgm·ml^–1 and from 27.3 to 15.3 g·24 h^–1 in plasma and urine, respectively, after 6 months on captopril therapy. Urinary protein excretion was decreased by about 48% and creatinine clearance remained unchanged throughout the study. Plasma triglycerides and cholesterol also remained unchanged, and glycosylated haemoglobin was significantly reduced from 13.8 to 10.2% after captopril.The results suggest that captopril is a useful drug to treat hypertension in patients suffering from diabetic nephropathy, as the decline in kidney function can be reduced without impairing glucose tolerance or the lipid profile.     

N-hexacosanol ameliorates streptozotocin-induced diabetic rat nephropathy

In this study we investigated the effects of N-hexacosanol on streptozotocin-induced rat diabetic nephropathy. Diabetes was induced in 8-week-old male Sprague-Dawley rats by administering an intraperitoneal injection of streptozotocin (50 mg/kg). The rats were divided into four groups and maintained for 8 weeks: control rats, diabetic rats without treatment with N-hexacosanol, and diabetic rats treated with N-hexacosanol (2 mg/kg and 8 mg/kg i.p. every day). Although N-hexacosanol failed to modify the diabetic status, increases in serum creatinine as well as in kidney weight were significantly reduced. The malonaldehyde and transforming growth factor beta-1 (TGF-beta1) concentrations as well as the protein kinase C (PKC) activities in the diabetic kidney were significantly higher than those of the control, which were decreased by treatment with N-hexacosanol. Histological examinations revealed that N-hexacosanol significantly ameliorated diabetic-induced tubulointerstitial pathological changes. Our data suggest that N-hexacosanol could prevent increases in the malonaldehyde and TGF-beta1 concentrations and PKC activities in the kidney, and ameliorate diabetic-induced nephropathy.     

Correlation between pharmacokinetics and pharmacologic effects of a new imidazole thromboxane synthetase inhibitor

A new imidazole derivative, sodium 4-[alpha-hydroxy-5-(1-imidazolyl)-2-methylbenzyl]-3,5-dimethylbenzoat e dihydrate (1; Y-20811), is a potent selective inhibitor of thromboxane (TX) synthetase and a candidate drug for preventing ischemic circulatory disorders. After oral dosing in beagle dogs, 1 persistently inhibited TX production, although the elimination of the drug was relatively rapid from plasma. The amount of drug distributed in platelets was small. However, 1 was eliminated from platelets very slowly (t1/2 = 41-130 h), the rate of elimination being comparable to the turnover rate of platelets. From the in vitro experiments, an obvious positive correlation was noted between the amount of the drug bound with TX synthetase in platelets and the inhibition of TX production. This correlation suggested that the small amount of 1 detected in platelets in vivo was large enough to inhibit TX production. From these observations, 1 is thought to dissociate extremely slowly from the active sites of TX synthetase. Consequently, the duration of the effect was dependent on the turnover of platelets.     

Characterization of rat glomerular thromboxane A2 receptors: comparison to rat platelets.

This study was designed to characterize rat glomerular thromboxane A2 (TxA2) receptors and compare them to rat platelet TxA2 receptors. The radioligand binding characteristics of the receptors were characterized using [125I][1S-(1 alpha,2 beta(5Z),3 alpha-(1E,3R*),4 alpha]-7-[3-(3-hydroxy-4-(4'-iodophenoxy)-1-butenyl)-7-oxabicyclo- [2.2.1]heptan-2yl]-5-heptenoic acid ([125I]BOP), a TxA2 agonist. Equilibrium binding with [125I]BOP, as well as competitive binding assays between [125I]BOP and 13-azapinane TxA2 receptors antagonists, were performed in rat glomerular membranes (RGM) and washed rat platelets (WRP). [125I]BOP identified a single class of TxA2 receptor sites in glomerular membranes with a Kd of 318 +/- 55 pM and a Bmax of 260 +/- 62 fmol/mg protein (n = 14). [125I]BOP was displaced by the TxA2 agonist 15S-hydroxy-11 alpha,9 alpha(epoxymethano)-prosta-5Z,13E-dienoic acid (U-46,619) (IC50 = 22 +/- 6 nM, n = 3), the antagonist SQ-29,548 (IC50 = 41 +/- 7 nM, n = 4), and stereoselectively by the antagonists (-)-9-chlorobenzyl-6-fluoro-1,2,3,4-tetrahydrocarbazol-1-yl acetic acid (L-657,925) (IC50 = 0.27 +/- 0.04 nM, n = 3) and (+)-9-chlorobenzyl-6-fluoro-1,2,3,4-tetrahydrocarbazol-1-yl acetic acid (L-657,926) (IC50 = 124 +/- 0 nM, n = 2). The ability of six 13-azapinane TxA2 antagonists to compete with [125I]BOP was evaluated. The rank orders for the 13-azapinanes showed no significant correlation between RGM and WRP.(ABSTRACT TRUNCATED AT 250 WORDS)