Effects of thromboxane synthetase inhibitors on aggregation of rabbit platelets.

Thromboxane (TX) synthetase activity was selectively inhibited by (E)-3-[4-(1-imidazolylmethyl)phenyl]-2-propenoic acid hydrochloride monohydrate (OKY-046) and sodium (E)-3-[4-(3-pyridylmethyl)phenyl]-2-methyl-propenoate (OKY-1581) (OKYs). Their IC50 for the rabbit platelet enzyme were found to be 11nM and 3nM respectively. Arachidonic acid (AA) or collagen induced platelet aggregation, and generated TXA 2 and prostaglandins (PGs) in rabbit platelets. OKYs inhibited platelet aggregation and TXA2 generation without affecting PGs generation, while aspirin inhibited platelet aggregation, and TXA2 and PGs generation. There was a parallel relation between the degree of inhibition of platelet aggregation and TXA2 generation by OKYs, but the inhibitory effects of aspirin on platelet aggregation was related to that on both TXA2 and PGs generation. However, OKYs and aspirin did not inhibit ADP-induced platelet aggregation which did not involve the generation of TXA2 and PGs. These results suggested that TXA2 generation is related to platelet aggregation induced by AA or collagen, and that the inhibitory effect of OKYs on platelet aggregation is due to the inhibition of TX synthetase.

[Prostaglandins: synthetic and pharmacological studies and development].

The therapeutic use of prostaglandins (PGs) which contain various biological activities and are unstable was successfully achieved. PGs were produced in a large scale according to the Corey method and could be stabilized by the formation of a clathrate compound with cyclodextrin, which enabled the production of marketable form of highly pure PGs. Diligence in the development of native PGs and their structural analogs for human therapy resulted in the following six drugs now being on the market in Japan: PGF2 alpha as the first drug of PGs in the world which induces labor; PGE2 as an orally active labor inducing drug; PGE1 for the treatment of peripheral vascular diseases; gemeprost for therapeutic abortion in the middle-term; ornoprostil, as an oral anti-ulcer agent; limaprost for the treatment of peripheral vascular diseases as an oral agent.

[Effects of 16,16-dimethyl-trans-delta 2-PGE1 methyl ester (ONO-802) on reproductive function (author's transl)].

Effects of ONO-802 on maintenance of pregnancy, luteal function and ovulation were investigated. In pregnant rats, ONO-802 given i.p. showed antinidatory, abortifacient and strong labor-inducing effects with treatment on day 2, after day 17 and on day 21 of gestation, respectively. The abortifacient effect was not apparent when treatment was given from day 4-15. PGE1 had an antinidatory effect, PGF2 alpha had an abortifacient and labor-inducing effects after implantation, and PGE2 had both these effects. PGF2 alpha and PGE2 showed a luteolytic effect in rats, while ONO-802, similarly to the findings with PGE1, had no such effect. In pregnant rabbits, intraperitoneal ONO-802, exhibited antinidatory and abortifacient effects after implantation. Abortifacient effects were more potent with the progression of pregnancy of pregnancy though relatively large doses of ONO-802 were required. A significant decrease in peripheral blood progesterone level was observed in the group on high doses but the abortifacient effect of ONO-802 did not always depend on the decreases in the levels of progesterone. In cycling, spontaneously ovulating rats, the high doses of ONO-802 suppressed spontaneous ovulation when these doses were given two at 14:30 and 15:30 on the day of proestrus. ONO-802 did not inhibit the HCG-induced ovulation and the ovulation suppressed by ONO-802 was recovered by PGE2 or HCG.

ONO-3144, a new anti-inflammatory drug and its possible mechanism of action.

Anti-inflammatory activities of ONO-3144 have been studied in various experimental models. This compound showed an inhibitory effect on increased vascular permeability and acute inflammation. In the carrageenin test the activity of ONO-3144 was comparable to that of indomethacin (IM), while in the dextran, albumin, yeast and scald edema test it was more potent than that of IM. Unlike IM, phenylbutazone (PB) and tiaramide (TI), ONO-3144 showed marked inhibitory effects on H2O2-induced hemolysis and lipid peroxidation. In the prostaglandin (PG) biosynthesis series, ONO-3144 did not inhibit cyclooxygenase activity but stimulated PG hydroperoxidase activity, facilitated conversion to PGH2 and also inhibited thromboxane (Tx) synthetase. The findings suggest that ONO-3144 is potentially a new type of anti-inflammatory drug. Possible sites of action of ONO-3144 are discussed.

Effects of a new aldose reductase inhibitor on various tissues in vitro.

A new aldose reductase inhibitor, ONO-2235 [(E)-3-carboxymethyl-5-[(2E)-methyl-3-phenylpropenylidene] rhodanine], was found to possess a potent inhibitory activity of aldose reductase, partially purified from rat lens (IC50 = 1.0 X 10(-8) M) and human placenta (IC50 = 2.6 X 10(-8) M). Against rat lens aldose reductase, ONO-2235 exhibited uncompetitive inhibition as previously observed with 7-hydroxy-4-oxo-4H-chromen-2-carboxylic acid. Sorbitol accumulation in the isolated rat lenses, sciatic nerves and human erythrocytes were all effectively inhibited during incubation with high concentrations of glucose (28-50 mM) by ONO-2235 at a concentration of about 10(-6) M. Because the accumulation of sorbitol has been reported to play an etiological role in the development of diabetic complications, the results suggest that ONO-2235 may prove to be useful in preventing and improving some diabetic complications.

[Effects of 16,16-dimethyl-trans-delta 2-PGE1 methyl ester (ONO-802) on uterine motility (author's transl)].

In rats on day 20 of pregnancy, ONO-802 exerted a uterine contractile effect when 0.2 microgram/kg was given i.v. and also with an intrauterine administration of 0.5 ng, s.c. administration of 1 microgram/kg and vaginal administration of 10 microgram/kg. The contractile activity of ONO-802 was 100-1000 times more potent than that of PGE2 alpha and was long-acting. Intravenous PGE1 or PGE2 induced a transient contraction followed by inhibition of spontaneous uterine motility in nonpregnant rats and in those with an early pregnancy. In nonpregnant hamsters, a relaxation was seen. ONO-802, similar to PGF2 alpha, showed a contractile effect regardless of states of nonpregnancy and pregnancy, both rats and hamsters. IN rats, a contractile threshold dose of ONO-802 was similar from day 15 to day 21 of pregnancy. Oxytocin produced an acute decrease in this threshold dose on phentolamine or methysergide, but was inhibited by papaverine, dibutyryl cAMP, salbutamol and verapamil. These results suggest that uterine contraction induced by ONO-802 differs from the contractions induced by PGE1, PGE2, and oxytocin, that ONO-802 does not induce endogenous PGs, and that the effect of ONO-802 is not mediated by the autonomic nervous system.

Effect of a new aldose reductase inhibitor, (E)-3-carboxymethyl-5-[(2E)-methyl-3-phenylpropenylidene]rhodanine (ONO-2235) on peripheral nerve disorders in streptozotocin-diabetic rats.

A new aldose reductase inhibitor, (E)-3-carboxymethyl-5-[(2E-methyl-3-phenylpropenylidene]rhodanine (ONO-2235) was administered orally to streptozotocin-diabetic rats (60 mg/kg IV) for 14 days and its effect on motor nerve conduction velocity studied. The compound significantly improved motor nerve conduction velocity of diabetic rats at a minimal dose of 10 mg . kg-1 . day-1 (treated 28.8 +/- 0.5 versus untreated 23.2 +/- 4.7 m/s, p less than 0.01). The sorbitol content of the sciatic nerve and red blood cells measured after 2 weeks was concomitantly reduced in ONO-2235-treated rats (sciatic nerve: 120 +/- 13 versus 595 +/- 146 nmol/g wet weight; red blood cell: 91 +/- 21 versus 165 +/- 39 nmol/g haemoglobin; p less than 0.01 in both 20 mg . kg-1 . day-1-treated versus untreated animals). These results suggest that sorbitol accumulation might contribute to the development of peripheral nerve dysfunction in acutely diabetic animals and the new aldose reductase inhibitor could be a potential drug for therapy of diabetic neuropathy.

Pharmacological evaluation of OP 1206, a prostaglandin E1 derivative, as an antianginal agent.

Effects of OP 1206 were studied on the cardiovascular system and platelet functions to assess OP 1206 as an antianginal agent. OP 1206 given orally at more than 100 micrograms/kg relieved vasopressin-induced ST depression of rat electrocardiogram (ECG), an animal model of angina pectoris, concomitant with slight hypotension. Intra-coronary injection of OP 1206 (1-100 ng/kg) in dogs resulted in a remarkable increase of coronary blood flow without any influence on heart rate, blood pressure, myocardial oxygen consumption and redox potential. Resistance in both large and small vessels of dog coronary artery was decreased by intravenous injection of OP 1206 (1-3 micrograms/kg). Platelet aggregation, adhesiveness, bleeding time, and thrombocytopenia induced by ADP and collagen infusion in guinea-pigs were inhibited by oral administration of OP 1206 at the same doses or doses less than those relieving vasopressin-induced ST depression of ECG. These results suggest that OP 1206 contributes to the improvement of cardiac imbalance between oxygen demand and supply, and suppression of thrombus formation in atherosclerotic heart.

[Effects of 16,16-Dimethyl-trans-delta 2-PGE1 methyl ester (ONO-802) on uterine, placental and ovarian circulation (author's transl)].

Doses of the drugs which produce uterine contraction were given intravenously to various species of animals. Placental and ovarian circulations were measured by the thermocouple method and/or microangiography. Uterine arterial blood flow (UABF) was measured by the electromagnetic flowmeter. Both placental blood flow (PBF) and UABF decreased with the administration of ONO-802, PGE1 or PGF2 alpha to to rabbits and dogs. Oxytocin and noradrenaline also decreased PBF in rabbits. ONO-802 or PGE1 lowered arterial blood pressure (BP) in rats, rabbits and dogs. PGE2 alpha elevated BP in rats and dogs and lowered it in rabbits. Oxytocin produced no changes in PB while noradrenaline elevated BP in rabbits. Ovarian blood flow in pregnant rabbits was reduced by ONO-802, PGE1 or PGF2 alpha. Little influence was seen with oxytocin. Regarding the luteal microvasculature in pregnant rats, ONO-802, PGF2 alpha and noradrenaline exhibited vasoconstricting effects. PGF2 alpha induced abortion and decreased plasma progesterone levels. These results suggest that the inhibitory effects of ONO-802 on the uterine and placental circulation are strongly influenced by the uterine contractile effect and that the inhibitory effect on the ovarian circulation in rats is one of pharmacological effects not concerned with the abortifacient or luteolytic effect.