Inhibition of platelet aggregation with intravenous and oral administration of a carboprostacyclin analogue, 15-cyclopentyl-omega-pentanor-5(E)-carbacyclin (ONO 41483) in man

Prostaglandin E and analogs of prostacyclin influencing superoxide production by the human neutrophil NADPH oxidase system

The effects of prostaglandin (PG) E1 and I2 analogs (OP-41483 and OP-2507) on the superoxide generation of human neutrophil NADPH oxidase (EC 1.6.99.6) in both whole-cell and cell-free systems were investigated. In a whole-cell system, OP-2507 inhibited the superoxide generation by neutrophils exposed to phorbol myristate acetate concentration-dependently through its superoxide-scavenging action. The concentration of the drug required for 50% inhibition of the oxidase (IC50) was 21 microM. In a cell-free system, however, the drug in concentrations of < 100 microM did not inhibit the activation of NADPH oxidase by sodium dodecyl sulfate because of its inactivation by the detergent. Although PGE1 and OP-41483 did not inhibit the superoxide production by stimulated neutrophils in a whole-cell system, they both inhibited the activation of NADPH oxidase in a cell-free system concentration-dependently, with IC50 values of 44 and 170 microM, respectively. In addition, in the cell-free system, the Km value for NADPH of the oxidase was unchanged by PGE1. The results suggest that the PGI2 analog, OP-2507, is a possible superoxide-scavenger and that PGE1 inhibits the NADPH oxidase activation by sodium dodecyl sulfate in a cell-free system concentration-dependently.

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.

Effect of oral administration of a prostacyclin analog (OP-41483) on pulmonary function and bronchial responsiveness in stable asthmatic subjects

To examine whether prostacyclin has an attenuating effect on nonspecific bronchial responsiveness in asthma, we measured provocative concentration of methacholine producing a 20% fall in forced expiratory volume in 1 second (PC20-FEV1) before and after oral administration of a chemically stable prostacyclin analog (OP-41483) (200 micrograms 4 times a day for 4 days) in 8 patients with stable asthma. Neither baseline pulmonary function nor PC20-FEV1 significantly improved after the treatment. These results suggest that prostacyclin may have no direct effect on bronchial responsiveness in asthmatics. Further studies using more potent and long-lasting prostacyclin mimetic will be needed to confirm the conclusion.

The effects of a prostacyclin analog OP-41483 on pulmonary oxygen toxicity in an isolated heart-lung autoperfusion model

Using an isolated canine heart-lung autoperfusion model, the effect of prostacyclin analog (OP-41483) on pulmonary oxygen toxicity was investigated. Twenty-four mongrel dogs were divided into four groups. Groups 1 and 2 inspired oxygen at concentrations (FiO2) of 0.95 and 0.6, respectively, while groups 3 and 4 received OP-41483 (0.1 micrograms/kg/min) in addition to FiO2 of 0.95 and 0.6. Autoperfusion was performed for five hours, and during the experiments the systolic blood pressure was maintained at 100 mmHg and the cardiac output at 40 ml/kg/min. After five hours of perfusion, PaO2 decreased significantly (P less than 0.01) from 410 +/- 49 mmHg to 237 +/- 38 mmHg in group 1, and also decreased significantly (P less than 0.01) from 368 +/- 44 mmHg to 243 +/- 26 mmHg in group 2. However, no significant changes in PaO2 were observed in groups 3 and 4. The pathological examinations clearly revealed perivascular edema and vascular dilation in groups 1 and 2, whereas no abnormal pathological findings were seen in groups 3 and 4. The above results indicate that OP-41483, when administered at the low dose of 0.1 micrograms/kg/min, induces no circulatory changes and exerts an effective action with respect to the prevention of pulmonary edema.

Mechanism of the cytoprotective effect of prostaglandin I2 and its analogue in human platelets

The responsiveness of washed human platelets to thrombin was well preserved up to 72 and 96 hours, when they were stored at 4 degrees C with prostaglandin I2 (PGI2) and its stable analogue OP-41483, respectively, while the washed platelets stored with sodium citrate completely lost their responsiveness to thrombin at 48 hours. The effect of PGI2 or the analogue on the resting level of intraplatelet Ca2+ concentration ([Ca2+]i) was investigated, utilizing fluorescent Ca2+ indicator quin 2. PGI2 lowered the resting [Ca2+]i in a dose related manner in the presence or absence of the extracellular Ca2+. The similar results were obtained when OP-41483 was added to the quin 2 loaded platelets. From these results, it was concluded that the lowering of the resting [Ca2+]i may be the prerequisite for the cytoprotective effect of PGI2 or OP-41483.

Inhibition of platelet aggregation and antagonism of vasopressin-induced ECG changes in primates by a carboprostacyclin analogue, ZK 36374

A chemically stable carboprostacyclin analogue, ZK 36374 has been compared with two other prostacyclin derivatives with respect to ADP-induced in vitro aggregation of baboon and human platelets and ex vivo platelet aggregation in the baboon. ZK 36374 was also tested on the systemic arterial blood pressure of the baboon and against vasopressin-induced ECG changes in primates. Compared to the other two compounds, ZK 36374 displayed enhanced anti-platelet aggregating activity; there was dissociation between this property and its hypotensive potency. ZK 36374 antagonized the vasopressin-induced ECG changes. These results indicate that ZK 36374 possesses therapeutic potential in vascular disease including that affecting the coronary vessels.