Effect of prostaglandin E1 on platelet behaviour in vitro and in vivo

Desmopressin, Misoprostol, nor Carboprost Affect Platelet Aggregability Following Traumatic Brain Injury and Aspirin

INTRODUCTION

Desmopressin (DDAVP) has been utilized clinically in patients taking aspirin (ASA) to improve drug-induced platelet dysfunction. Misoprostol and carboprost, prostaglandin analogs commonly used for postpartum hemorrhage, may also induce platelet aggregation. The aim of this study was to determine the effects of DDAVP, misoprostol, and carboprost administration on platelet aggregability following traumatic brain injury (TBI) in mice treated with ASA.

METHODS

Male C57BL/6 mice were randomized into seven groups (n = 5 each): untouched, ASA only, Saline/TBI, ASA/TBI, ASA/TBI/DDAVP 0.4 μg/kg, ASA/TBI/misoprostol 1 mg/kg, and ASA/TBI/carboprost 100 μg/kg. TBI was induced via a weight drop model 4-h after ASA (50 mg/kg) gavage. Mice were given an intraperitoneal injection of DDAVP, misoprostol, or carboprost 10 minutes after TBI. In vivo testing was completed utilizing tail vein bleed. Mice were sacrificed 30-min posttreatment and blood was collected via cardiac puncture. Whole blood was analyzed via Multiplate impedance aggregometry, rotational thromboelastometry, and TEG6s.

RESULTS

Mice receiving misoprostol after ASA/TBI demonstrated decreased tail vein bleeding times compared to ASA only treated mice. However, mice treated with misoprostol following ASA and TBI demonstrated decreased platelet aggregability compared to untouched mice and TBI only mice within the arachidonic acid agonist pathway. By contrast, DDAVP and carboprost did not significantly change platelet aggregability via adenosine diphosphate or arachidonic acid following ASA and TBI. However, DDAVP did decrease the platelet contribution to clot via rotational thromboelastometry.

CONCLUSIONS

Reversal of medication-induced platelet inhibition has become increasingly controversial after TBI. Based on these results, DDAVP, misoprostol, nor carboprost consistently improve platelet aggregability following TBI in those also treated with ASA.

Store-operated Ca2+ Entry Facilitates the Lipopolysaccharide-induced Cyclooxygenase-2 Expression in Gastric Cancer Cells

Helicobacter pylori has been identified as one of the major causes of chronic gastritis, gastric and duodenal ulcers, and gastric cancer. Lipopolysaccharide (LPS) is a major component of the outer membrane of gram-negative bacteria, and H. pylori LPS might play an exclusively important role in activating inflammatory pathways in monocytes and macrophages. To study the role of LPS in the underlying mechanism of inflammatory responses, we established an in vitro model using the human AGS gastric cancer cell line. We found that LPS mediates inflammation through setting off a cascade of events: activation of the store-operated calcium (SOC) channel, initiation of downstream NF-κB signaling, and phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2). Phosphorylated ERK1/2 promotes the nuclear translocation of NF-κB, and eventually elevates the expression level of COX-2, a major inflammatory gene.

On the interaction of fluorophore-encapsulating PEGylated lecithin liposomes with hamster and human platelets

Polyethylene glycol (PEG)-grafted phosphatidylcholine liposomes are used as drug carriers due to their low immunogenicity and prolonged circulation time. The interaction between sterically stabilized lecithin liposomes and platelets has not been investigated before, and deserves to be subjected to scrutiny inasmuch as the uptake of liposomes by platelets could be detrimental for drug delivery and primary hemostasis. Consequently, the interaction between resting and convulxin-activated hamster and human platelets and calcein- or 5,6-carboxyfluorescein-encapsulating PEGylated liposomes composed of distearoyl- and dipalmitoyl phosphatidylcholine and PEG-derivatized distearoyl phosphatidylethanolamine was investigated by flow cytometry, confocal microscopy, and a glass capillary thrombosis model. Fluorescently labeled liposomes of the same composition were subsequently assayed in vivo after 15 and 45 min of systemic circulation. Neither resting nor activated hamster and human platelets interacted with liposomes at 0.70 mM lipid concentration. An absence of any interaction was corroborated in the in vivo experiments. Alternatively, flow cytometry assays evinced that human platelets interact with liposomes at lipid concentrations of >or=1.35 mM. These interactions were more profound for activated platelets than resting platelets. We conclude that the use of PEGylated lecithin liposomes at lipid concentrations of <1.35 mM has no detrimental impact on liposomal drug delivery based on PEGylated lecithin liposomes, but that these drug carriers may be associated with a reduced targeting efficacy or compromised primary hemostatic system when used at concentrations of >or=1.35 mM. In contrast, these drug carriers may become valuable in thrombosis- and drug delivery-related research and applications at concentrations of >or=1.35 mM.

The effects of OP-1206 alpha-CD on walking dysfunction in the rat neuropathic intermittent claudication model

IV prostaglandin E1 improves clinical symptoms in patients with spinal canal stenosis. In the present study, we assessed the effects of OP-1206 alpha-CD, an orally active prostaglandin E1 analog, on walking dysfunction in the rat neuropathic intermittent claudication model. To induce spinal stenosis, two pieces of silicon rubber were placed in the lumbar (L4-6) epidural space in rats. Postsurgical walking function was measured using a treadmill apparatus. Spinal cord blood flow (SCBF) and skin blood flow (SKBF) were measured using a laser-Doppler flowmeter. OP-1206 alpha-CD was administered orally bid for 11 days from postoperative Day 3. In Control nontreated rats, a significant walking dysfunction was observed from Day 1 after the induction of spinal stenosis and persisted for 14 days when compared with the Sham-Operated group. On postoperative Day 15, SCBF revealed a significant reduction in the territory of spinal stenosis, although SKBF was not affected. OP-1206 alpha-CD significantly improved walking dysfunction on postoperative Days 5 (300 microg/kg), 7 (150 and 300 microg/kg), and 14 (150 and 300 microg/kg) when compared with the Vehicle-Treated group. On postoperative Day 15, the decrease in SCBF was significantly (150 and 300 microg/kg) improved by OP-1206 alpha-CD treatment, albeit SKBF remained unaffected. These data show that oral treatment with OP-1206 alpha-CD is effective in improving walking dysfunction induced by spinal canal stenosis, and this therapeutic effect is likely mediated by improved SCBF at the territory of spinal stenosis.

IMPLICATIONS

Intermittent motor dysfunction is a clinical symptom associated with partial spinal compression. The present study provides evidence that oral treatment with the prostaglandin E1 analog (OP-1206 alpha-CD) is effective in improving motor dysfunction and spinal cord blood flow in rats with spinal compression.

Prostacyclin (PGI2) inhibits the formation of platelet thrombi in arterioles and venules of the hamster cheek pouch. 1977

Isolated rings of hamster aorta produced an unstable substance which inhibited platelet aggregation in vitro and had the same characteristics as prostacyclin.

Prostacyclin inhibited adenosine diphosphate (ADP)-induced aggregation of hamster platelets in vitro.

The effects of prostacyclin on ADP-induced platelet thrombi in the microcirculation of the hamster cheek pouch were studied with a television microscope.

Prostacyclin caused a dose-dependent increase in the time of iontophoretic application of ADP which was required to induce platelet thrombi formation and embolization in venules (30 to 40 μm diameter).

Prostacyclin caused a dose-dependent reduction in the total time during which ADP-induced thrombi were observed following local electrical damage to arterioles (40 to 80 μm diameter).

Thrombus formation in venules and arterioles was abolished by 500 ng/ml prostacyclin in the Krebs solution superfusing the hamster cheek pouch.

Prostacyclin was approximately twenty times more potent than prostaglandin E₁ in preventing thrombus formation in the microcirculation.

Clinical effectiveness of an ointment containing prostaglandin E1 for the treatment of burn wounds

This report discusses the effectiveness of conservative treatment of burns using applications of prostaglandin E1 (PGE1) containing ointment (PGE1 ointment) to the wound site. Fourteen patients with superficial dermal burns (SDB), deep dermal burns (DDB) and full-thickness dermal burns (DB), who were treated with repeated applications of this ointment, showed rapid epithelialization of the affected tissue. Hypertrophic scarring after epithelialization was less than that expected after other therapies. The degree of scarring was graded as 'none', 'mild', 'moderate' or 'severe'. The results of this therapy revealed no scarring in two sites (8.7 per cent), mild scarring in 16 sites (69.6 per cent), moderate scarring in one site (4.3 per cent) and severe scarring in four sites (17.4 per cent) out of 23 sites distributed among the patients. The application of PGE1 ointment in combination with skin grafting surgery was found to improve functional and aesthetic results in the patients with DDB and DB, by minimizing the area of the donor site; it was especially useful for children with extensive burns because of the shortage of available tissue as donor site material for skin grafting.

Effect of topical application of a stable prostacyclin analogue, SM-10902 on wound healing in diabetic mice

The mechanism of wound healing induced by topical application of an ointment containing a new stable prostacyclin analogue, SM-10902 ((+)-methyl[2-[(2R,3aS,4R,5R, 6aS)-octahydro-5-hydroxy-4-[(E)-(3S,5S)-3-hydroxy-5-methyl-1- nonenyl]-2-pentalenyl] ethoxy] acetate), was investigated in the full-thickness wounds of genetically diabetic mice (db/db mice). The db/db mice treated with SM-10902 ointment (1, 10 and 100 micrograms/g) showed greater decrease in wound lesion area not covered with epidermis and fewer complete healing days than those treated with ointment base, and the effects of this prostacyclin analogue were greater than those of lysozyme chloride ointment (50 mg/g, Reflap ointment). SM-10902 ointment increased skin blood flow in the central site of the wound with development of wound healing. Histological evaluation of wounds revealed that SM-10902 ointment increased the capillary number during the early stage of the wound-healing process. These results suggest that SM-10902 ointment promotes wound healing through the stimulation of angiogenesis and the improvement of blood flow in neovascularization of repairing wound and may be useful in the treatment of skin ulcers caused by peripheral circulatory insufficiency.

Antiplatelet functions of a stable prostacyclin analog, SM-10906 are exerted by its inhibitory effect on inositol 1,4,5-trisphosphate production and cytosolic Ca++ increase in rat platelets stimulated by thrombin

The mechanism of the antiplatelet functions of SM-10906, the active form of the 3-oxa-methano-prostaglandin (PG) I1 analog SM-10902, was examined in rat platelets. SM-10906 activated adenylate cyclase in crude membrane fractions, and inhibited platelet aggregation and release of adenine nucleotides stimulated by thrombin. SM-10906 also inhibited malondialdehyde production induced by thrombin, but not that induced by arachidonic acid. This may account for its inhibitory effects on phospholipase A2. SM-10906 prevented thrombin-induced inositol 1,4,5-trisphosphate production, Ca++ mobilization from intracellular Ca storage and 45Ca++ influx into platelets, which were all reversed by pretreatment with the adenylate cyclase inhibitor 2',5'-dideoxyadenosine. PGI2 and PGE1 have the same antiplatelet profiles in the order of PGI2 > or = SM-10906 > PGE1. These results indicate that SM-10906 as well as PGI2 and PGE1 may exert antiplatelet activities by stimulating adenylate cyclase to prevent thrombin-induced phospholipase C and A2 activations and increase in cytosolic Ca++ level.

OP-1206, a prostaglandin E1 derivative, attenuates the thermal hyperesthesia induced by constriction injury to the sciatic nerve in the rat

Nerve ischemia induces wallerian degeneration and peripheral neuropathy, the nerve constriction injury induces thermal hyperesthesia. Nerve ischemia is one possible mechanism in the development of thermal hyperesthesia in the nerve constriction injury model. Prostaglandin E1 increases tissue blood flow. In the present study, the authors examine the role of nerve ischemia in the maintenance of the thermal hyperesthesia induced by nerve constriction injury by orally administering OP-1206, a prostaglandin E1 derivative. A nerve constriction injury model was created by making four loose ligations around the rat sciatic nerve, which induces thermal hyperesthesia in the ligated paw in 2-5 days. OP-1206, was administered six times (Day 7, one time; Day 8, two times; Day 9, two times; Day 10, one time). A single administration of OP-1206 had no effect on the thermal hyperesthesia. Six hours after the sixth-administration of OP-1206, the level of the thermal hyperesthesia was attenuated in a dose-dependent manner, and this effect lasted more than 1 day after the last drug administration. These data indicate that nerve ischemia plays an important role in maintaining the thermal hyperesthesia induced by nerve constriction injury in the rat.

Effect of prostaglandin E1 analogue administration on peripheral skin temperature at high altitude

The effect of prostaglandin E1 analogue on peripheral skin temperature was examined at high altitude, where local cold injuries are common owing to severe environmental conditions. The peripheral skin temperature at rest was significantly lower at higher altitudes. Oral administration of the prostaglandin E1 analogue limaprost reversed this temperature decrease, probably by enhancement of peripheral circulation. The temperature recovery rate after a cold water challenge was also improved after the administration of limaprost. This oral type of prostaglandin E1 analogue is strongly recommended as an effective prophylactic and therapeutic vasodilator for local cold injuries at high altitudes.

Effect of Prostaglandin E1 Analogue Administration on Peripheral Skin Temperature at High Altitude

The effect of prostaglandin E1 analogue on peripheral skin temperature was examined at high altitude, where local cold injuries are common owing to severe environmental condi tions. The peripheral skin temperature at rest was significantly lower at higher altitudes. Oral administration of the prostaglandin E1 analogue limaprost reversed this temperature decrease, probably by enhancement of peripheral circulation. The temperature recovery rate after a cold water challenge was also improved after the administration of limaprost. This oral type of prostaglandin E 1 analogue is strongly recommended as an effective prophylactic and therapeutic vasodilator for local cold injuries at high altitudes.

Prostaglandin E1 does not accelerate rTPA-induced thrombolysis in acute myocardial infarction

Fifteen patients who arrived between 6 and 24 hours after the onset of acute myocardial infarction and who were found to have totally occluded coronary arteries, received aspirin, heparin, and tissue plasminogen activator given over 3 hours. Eight patients were randomly assigned to receive intravenous prostaglandin E1, 20 ng/kg/min for 6 hours, while seven patients received placebo infusion. Coronary arteriography begun immediately before the start of tissue plasminogen activator and repeated every 15 minutes revealed restoration of antegrade flow in two of eight (25%) patients treated with prostaglandin E1 and in two of seven (28%) patients receiving placebo. Pharmacologic sampling of tissue plasminogen activator levels were performed at baseline and 30, 45, 60, 75, 90, 135, 180, 190, 210, and 240 minutes afterwards for assessment of tissue plasminogen activator antigen. There was no difference in fibrinogen levels and no difference in tissue plasminogen activator antigen levels at these time periods. Clearance values of tissue plasminogen activator were calculated and were not different between the two groups. These data do not support the use of prostaglandin E1 for the acceleration of reperfusion in patients receiving tissue plasminogen activator for acute myocardial infarction.

Pharmacological approaches to the treatment of intermittent claudication

Intermittent claudication is a common condition of the elderly, occurring in 3 to 20% of individuals over the age of 65 years. Although local disease is usually benign, life expectancy in patients with intermittent claudication is reduced by approximately 10 years due to associated cardiovascular mortality. Several classes of drugs have been used in intermittent claudication, but clinical studies evaluating their efficacy leave much to be desired. Pentoxifylline (oxpentifylline), a rheological agent, and naftidrofuryl, an enhancer of aerobic metabolism, are the 2 most widely investigated and utilised drugs. The combined results of 10 placebo-controlled studies with pentoxifylline and 4 with naftidrofuryl estimate increases in claudication distances of 51 and 42%, respectively. However, due to publication bias, these figures are probably overestimates of the true benefit from treatment with these drugs. It is likely that any benefit from pentoxifylline or naftidrofuryl is small and of little clinical importance. The suggestion that naftidrofuryl has greater efficacy in older patients remains unproven. Other classes of drugs including vasodilators, antiplatelet drugs, anticoagulants and prostaglandins have not been shown to be effective. Only 2 approaches to the management of intermittent claudication have been shown convincingly to be of benefit: stopping smoking and exercising regularly.

Prostaglandin E1 and carbon dioxide reactivity during cerebral aneurysm surgery

The purpose of this study was to evaluate the effect of prostaglandin E1 (PGE1) on CO2 reactivity during cerebral aneurysm surgery in 37 patients under neuroleptoanaesthesia (NLA). The patients were divided into two groups based on the timing of surgery (A: late surgery B: early surgery). In the early surgery group, aneurysm surgery was performed within three days of subarachnoid haemorrhage (SAH) and in the late surgery group surgery was performed more than four days after SAH. Presurgical neurological status was worse in the early surgery group than in the late surgery group (P less than 0.01). Local cerebral blood flow (LCBF) measurements were made using a thermal gradient blood flow meter. Hypotension was induced by PGE1 administration at an initial dose of 0.1 micrograms.kg-1.min-1 and adjusted to maintain the mean arterial pressure (MAP) at about 70 mmHg. The CO2 reactivity was calculated by the % change in LCBF divided by the change in PaCO2 (% delta LCBF/delta PaCO2 (%.mmHg-1)). LCBF, heart rate and mean arterial blood pressure were measured during and after PGE1 infusion. Carbon dioxide reactivity was measured before, during and after PGE1 administration. The LCBF did not change throughout the study but CO2 reactivity was greater in Group A (before hypotension: 2.74 +/- 0.85 %.mmHg-1, during hypotension: 2.54 +/- 0.73 % .mmHg-1, after hypotension: 2.59 +/- 1.17 %.mmHg-1) than in group B (before hypotension: 1.54 +/- 0.57%.mmHg-1, during hypotension: 1.56 +/- 0.59 %.mmHg-1, after hypotension: 1.49 +/- 0.42%.mmHg-1) (P less than 0.01). Outcome which was graded by Glasgow Outcome Scale at discharge, was better in Group A (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of TFC-612, a 7-thia prostaglandin E1 derivative, on platelet function

The anti-platelet activities of TFC-612, methyl 6-(((1R, 2S, 3R)-3-hydroxy-2-((1E, 3S, 5R)-3-hydroxy-5-methyl-1-nonenyl)-5- oxocyclopentyl) thio)hexanoate, were compared to prostaglandin E1 (PGE1). TFC-612 inhibited human, guinea-pig and rabbit platelet aggregation induced by ADP, collagen or epinephrine with potency 1-8 times that of PGE1. TFC-612 also inhibited thrombin induced (14C) serotonin release in rabbit platelets. Platelet aggregation was dose dependently inhibited 1 hr after oral administration of TFC-612 (0.32-1.0 mg/kg) and the inhibition lasted up to 6 and 24 hours at 0.32 and 1.0 mg/kg, respectively, in guinea-pigs. In contrast, PGE1 had no effect with oral administration at a dose of 3.2 mg/kg. TFC-612 (0.32-3.2 micrograms/kg, i.v.) induced platelet disaggregation of thrombi on Achilles tendon in the extracorporeal shunt model in cats. In addition, TFC-612 (1 mg/kg, po) inhibited the adhesiveness of guinea-pig platelets to a glass bead column ex vivo. TFC-612 increased cyclic AMP (cAMP) levels in rabbit platelets. Thus, the anti-platelet action of TFC-612 may be due to an increase in cAMP levels. These results indicate that TFC-612 might be an orally active anti-thrombotic drug.

The effects of TFC-612, a 7-THIA prostaglandin E1 derivative, on platelet function

The anti-platelet activities of TFC-612, methyl 6-(( 1R,2S,3R)-3-hydroxy-2-((1E,3S,5R)-3-hydroxy-5-methyl-1-nonenyl)-5- oxocyclopentyl) thio)hexanoate, were compared to prostaglandin E1 (PGE1). TFC-612 inhibited human, guinea-pig and rabbit platelet aggregation induced by ADP, collagen or epinephrine with potency 1-8 times that of PGE1. TFC-612 also inhibited thrombin induced (14C) serotonin release in rabbit platelets. Platelet aggregation was dose dependently inhibited 1 hr after oral administration of TFC-612 (0.32-1.0 mg/kg) and the inhibition lasted up to 6 and 24 hours at 0.32 and 1.0 mg/kg, respectively, in guinea-pigs. In contrast, PGE1 had no effect with oral administration at a dose of 3.2 mg/kg. TFC-612 (0.32-3.2 micrograms/kg, iv) induced platelet disaggregation of thrombi on Achilles tendon in the extracorporeal shunt model in cats. In addition, TFC-612 (1 mg/kg, po) inhibited the adhesiveness of guinea-pig platelets to a glass bead column ex vivo. TFC-612 increased cyclic AMP (cAMP) levels in rabbit platelets. Thus, the anti-platelet action of TFC-612 may be due to an increase in cAMP levels. These results indicate that TFC-612 might be an orally active anti-thrombotic drug.

Suppression of human synovial cell proliferation by dihomo-gamma-linolenic acid

Prostaglandin E1 (PGE1) and oils enriched in its precursor fatty acids suppress inflammation and joint tissue injury in several animal models. Since synovial cell proliferation is a hallmark of rheumatoid arthritis, we studied the effect of dihomo-gamma-linolenic acid (DGLA), an immediate precursor of PGE1, on the growth of human adherent synovial cells (ASC) in tissue culture. When stimulated by appropriate concentrations of recombinant interleukin-1 beta (rIL-1 beta), ASC proliferate and produce PGE. DGLA-enriched medium suppressed both baseline and rIL-1 beta-stimulated ASC growth fivefold, compared with medium supplemented with arachidonic acid. Indomethacin reduced the effect of the DGLA. Synovial cells incorporated the DGLA, and rIL-1 beta-stimulated cells that were incubated with DGLA exhibited a 14-fold increase in PGE1 (to 25.2 +/- 6.0 ng/ml, mean +/- SD) and a 70% decrease in PGE2 (to 25.2 +/- 4.2 ng/ml) compared with cells in control medium. At equivalent concentrations (5 x 10(-7) M), PGE1 increased the level of cellular cAMP to a greater extent than did PGE2 (16.8 +/- 2.0 pmoles versus 4.3 +/- 1.9 pmoles, mean +/- SEM). Exogenous PGE1 was also a more effective inhibitor of cell growth. Similarly, cAMP concentrations in cells exposed to DGLA for 6 hours were greater than concentrations in arachidonic acid-enriched cultures (17.8 +/- 3.3 pmoles versus 2.1 +/- 2.0 pmoles). These observations suggest that DGLA can restrain ASC growth, an effect which may be due to its capacity to increase PGE1 production and subsequent cellular cAMP concentration.

Effects of aspirin and prostaglandin E1 on in vitro thrombolysis with urokinase. Evidence for a possible role of inhibiting platelet activity in thrombolysis

The formation of thrombi in vivo includes the activation of both platelets and the coagulation cascade. Conventional thrombolytic therapy is primarily directed toward the dissolution of fibrin. To evaluate the possibility that platelet activity impairs the lysis of thrombi, we studied the effects of aspirin and platelet-deaggregating prostaglandin E1 on thrombolysis with urokinase. Combined platelet and fibrin thrombi were produced in vitro by adding CaCl2 and collagen (1 microgram/ml) to citrated platelet-rich plasma (250,000 platelets per microliters). Urokinase (500-10,000 units/ml) caused a dose-dependent weight loss of the thrombi that was maximal at 2,000 units/ml. The addition of aspirin (10-200 micrograms/ml) to platelet-rich plasma before thrombus formation markedly enhanced thrombolysis with urokinase. This effect was most pronounced at 20 micrograms/ml aspirin. However, when aspirin was added after completion of thrombus formation, no significant effect on thrombolysis was noted. Prostaglandin E1 (1-100 mumol/l) improved the lysis with urokinase of the combined platelet and fibrin thrombi. This effect was maximal at 20 mumol/l prostaglandin E1. When pure fibrin thrombi were produced in platelet-free plasma, prostaglandin E1 was without effect on lysis. Thus, in vitro lysis with urokinase of combined platelet and fibrin thrombi was enhanced by the addition of platelet-deaggregating prostaglandin E1 and by pretreatment with aspirin.

The influence of prostaglandin E1 on systemic and pulmonary haemodynamics after aortic surgery

The influence of a peroperative prostaglandin E1 (PGE1) infusion on systemic and pulmonary haemodynamics in a porcine model of aortic surgery was studied. Twenty-four pigs were randomised to PGE1 (100 ng/kg/min) or 0.9% Saline as placebo. Haemaccel was then infused to maintain a central venous pressure (CVP) of greater than 4 less than 6 mmHg and pulmonary artery wedge pressure (PAWP) of greater than 3 less than 5 mmHg. Standardised aortic surgery consisted of midline laparotomy, small bowel exteriorisation, 1.5 h aortic clamping and 1 h shock before resuscitation. Serial measurements of blood pressure (BP), cardiac output (CO), pulmonary vascular resistance (PVR), pulmonary shunt (A-V shunt), and arterial PO2 (PaO2) were recorded during and three days after surgery. Volume loading with Haemaccel prevented a significant fall in initial BP on PGE1 at 95.1 +/- 48 mmHg compared to 102 +/- 4.9 mmHg in control animals with similar CO in the two groups. Following release of the aortic clamp all animals became profoundly hypotensive with BP falling to 74.6 +/- 3.0 and 68.7 +/- 3.2 mmHg for PGE1 and placebo respectively, but CO was protected in those animals receiving PGE1 at 1.92 +/- 0.04 compared to 1.67 +/- 0.1 L/min/m2 on placebo and remained significantly higher following resuscitation and three days later (P less than 0.05). PGE1 also reduced the marked rise in pulmonary vascular resistance to 922 +/- 84 dynes-s/cm5/m2 during shock in control animals to only 555 +/- 30 (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Prostaglandin E1: a review

Work on the structure of prostaglandin E1 (PGE1), isolated from natural sources, was completed 25 years ago (1). Shortly after, methods for the chemical synthesis of PG with their natural configuration were developed in the laboratories of the UpJohn Company (2) and of E. J. Corey (3) and, by the late sixties, PGE1 became widely available. The information since accumulated about its biological and clinical effects is more substantial than for any other PG. This review will draw together some of this information, focusing on recent studies of its mechanisms of action.

Low-dose acetylsalicylic acid (ASA) plus dipyridamole versus dipyridamole alone in the prevention of stroke in patients with reversible ischemic attacks

A total of 243 patients who had reversible ischemic attacks (RIA) were submitted to clinical trial to determine whether dipyridamole (400 mg/day) (D) or aspirin (100 mg/48 hours) + dipyridamole (300 mg/day) (ASA + D) would produce significant reduction in the subsequent occurrence of RIA and completed stroke. One hundred and fifteen were selected for Group ASA + D and 71 were treated with dipyridamole only. The treatment groups were similar in relation to age, sex, risk factors, duration and presumed vascular territory of RIA, incidence of alterations of arterial supra-aortic trunks, cerebral infarct (CT scan), and platelet function. Patients were followed for a mean time of 21 months. At the end of the study, 21.7% of the ASA + D group and 19.7% in the D group had suffered new episodes of RIA or completed stroke (p = 0.88). Frequency of stroke (reversible ischemic neurologic deficit or completed stroke) was 7.8% in the ASA + D patients and 9.8% in the D patients (p = 0.83). Subgroup analysis did not show significant differences either. It is concluded that ASA + D has no significantly greater beneficial effect than that observed with D alone in the secondary prevention of atherothrombotic cerebral ischemia. However, a statistical Type II error cannot be excluded by the reduced number of recurrences.

Intracoronary prostaglandin E1 plus streptokinase in acute myocardial infarction

Fourteen patients with acute myocardial infarction (duration of chest pain 5 +/- 2 hours) received intracoronary infusion of prostaglandin E1 (PGE1) and streptokinase. Intracoronary PGE1 was followed by intracoronary streptokinase in 10 patients (group A), with successful recanalization in all patients. Of 4 patients in whom recanalization failed with intracoronary streptokinase given first (group B), 2 had successful recanalization after addition of intracoronary PGE1. Immediately after successful recanalization, left ventricular ejection fraction increased from 50 +/- 9% to 62 +/- 10% (p less than 0.0008), left ventricular end-diastolic pressure decreased from 20 +/- 10 to 16 +/- 10 mm Hg (p less than 0.05) and stroke volume index increased from 34 +/- 10 to 44 +/- 12 ml/m2 (p less than 0.02). Infarct segment shortening improved from 9 +/- 5 to 18 +/- 4% (p less than 0.0002). Transient hypotension in 1 patient was the only complication. Follow-up catheterization in recanalized patients at 2 to 10 days showed maintained improvement in left ventricular global and infarct segment function. Reocclusion occurred in 1 patient. Thus, intracoronary infusion of PGE1 was effective in establishing reperfusion in all patients when followed by streptokinase and was associated with immediately improved left ventricular global and regional function. PGE1 deserves further evaluation in acute myocardial infarction.

Regional platelet concentration in blood flow through capillary tubes

Platelet concentration was measured in samples from the various components of a bloodflow circuit, including the reservoir, the tube (with i.d. between 50 and 210 micron), and the discharge. The tube sample was collected by halting the flow and then flushing out a length of tube; thus, this sample collected equally from all radial locations. As the discharge sample was well mixed, it reflected the velocity field in the tube. Each reservoir sample was a traditional bulk collection. To ensure that the results represented the physical effects of flow on regional platelet concentration and could be interpreted with simple mass balance relationships, strong anticoagulation (sodium citrate and heparin) and platelet inhibition (prostaglandin E1) were used. Results for all tube diameters and for reservoir hematocrits from 5.5 to 77% and wall shear rates from 80 to 8000 sec-1 show that tubular platelet concentration is greater than reservoir or discharge platelet concentrations, which are equal. For platelet-rich plasma the tubular platelet concentration is decreased compared to the reservoir or discharge values. Mass balances show that the elevated tubular platelet concentration is due to an excess of platelets in radial locations with below average speeds; coupled with the need for red cells, this suggests that excess platelets have a near-wall location. Nonparametric statistical tests show that wall shear rate is a significant variable at a 0.05 confidence level; inner diameter is not found to be a significant variable, probably because of the limited diameter range studied and the experimental errors involved in determining platelet concentrations.

Separation and quantification of prostaglandins E1 and E2 as their panacyl derivatives using reverse phase high pressure liquid chromatography

Separation and quantification of prostaglandin E1 (PGE1) and prostaglandin E2 (PGE2) were achieved using reverse phase high performance liquid chromatography (HPLC). Panacyl bromide (p-(9-anthroyloxy)phenacyl bromide) (PAB) derivatives of PGE2 and PGE1 were prepared. Reverse phase HPLC using a linear gradient of 56% to 80% acetonitrile in water containing 0.10% acetic acid gave baseline resolution of the two derivatives. A 3 um diameter particle, C18 column provided good resolution and reproducible recoveries. Human synovial tissue cells were incubated with the precursor fatty acids for PGE1 or PGE2 and stimulated with a crude Interleukin 1 (IL-1) preparation. Cells grown in the presence of dihomogammalinolenic acid (DGLA), the precursor for PGE1, made significantly more PGE1 than cells grown in control medium or in the presence of arachidonic acid, precursor for PGE2. PGE2 synthesis was reduced when DGLA was added to cells (resting or IL-1-stimulated).

Haemodynamic effects of intra-arterial and intravenous administration of prostaglandin E1 in patients with peripheral arterial disease

The purpose of this study was to compare the haemodynamic effects of intra-arterial and intravenous prostaglandin E1 (PGE1) both injected and infused into ischaemic legs. Continuous intra-arterial infusion of PGE1 induced a significantly greater increase in skin temperature and blood flow than did intravenous drip infusion. Furthermore, intra-arterial infusion caused no steal phenomenon in the toe as indicated by skin temperature. On the other hand, toe skin temperature decreased during intravenous drip in 33 per cent of the legs tested. Continuous intravenous infusion also produced a significantly greater increase in toe skin temperature than did brief intravenous drip. In three of ten ulcers healed by continuous intra-arterial infusion, no definitive effect was obtained from continuous intravenous infusion even when it was repeated up to three times before continuous intra-arterial infusion. Intra-arterial injection of PGE1 caused no significant increase in toe skin temperature.

Misoprostol clinical pharmacology. Establishment of activity in man

Misoprostol has been evaluated in healthy subjects for both antisecretory and pharmacological activity. Doses used were determined initially from acute and chronic tolerance testing in healthy subjects. In the single dosage range of 50-200 micrograms, misoprostol inhibits gastric acid secretion in a dose-related manner both in the basal state and after stimuli such as histamine and standard test meals. The 200 micrograms dose differs significantly from placebo as an antisecretory agent. A preliminary study in six subjects suggested that the 400 micrograms dose does not produce a substantial increase in activity over the 200 micrograms dose. Furthermore, side-effects such as diarrhea and abdominal cramps appear to be dose related. The antisecretory action of misoprostol is maximal one hour after drug administration and is negligible after 4-5 hours. These factors have until now dictated a 50-200 micrograms q.i.d. dosing regimen for misoprostol in clinical trials against peptic ulcer. Misoprostol does not significantly affect platelet function in terms of ADP-, collagen- and thrombin-induced platelet aggregation. Measurements of FEV1, vital capacity, and peak expiratory flow rate have revealed that misoprostol has no significant bronchodilating or bronchoconstricting effect. Studies of endocrine function revealed only a slight rise within the normal range in serum cortisol in women.

The effect of prostaglandin E2 on histamine-stimulated calcium mobilization as a possible explanation for histamine tachyphylaxis in canine tracheal smooth muscle

Isolated strips of canine tracheal smooth muscle rapidly lost their responsiveness to histamine when placed in a zero calcium Krebs buffer. Responsiveness to acetylcholine, however, was not rapidly lost, and following 120 min of incubation in zero calcium buffer with frequent washes, 10% of the contractile response still remained. The kinetics of each loss of response suggest that primarily a loosely bound source of calcium is mobilized by histamine and a more tightly bound source is mobilized by acetylcholine. Consistent with these data were the effects of the calcium antagonist verapamil. In normal calcium Krebs solution, dose-response curves to histamine were markedly reduced by verapamil while acetylcholine responses were relatively unaffected. In calcium depleted tracheal strips, indomethacin potentiated the calcium dose-response curve, determined by incremental readdition of calcium in the presence of histamine (10(-4) M), with comparatively little effect on the calcium dose-response curve in the presence of acetylcholine (10(-6) M). Also, in indomethacin pretreated tracheal strips, a reduction in the histamine-calcium dose-response curve could be produced by exogenous addition of 2.8 X 10(-9) M and 2.8 X 10(-8) M PGE2. In the acetylcholine-calcium responses there was a significant reduction only at 2.8 X 10(-8) M PGE2. These data suggest that histamine mobilizes primarily a loosely bound, possibly extracellular source of calcium necessary for contraction, and this histamine-stimulated calcium mobilization is sensitive to the effects of PGE2.

Comparison of the vasodepressor action of ZK 36 374, a stable prostacyclin derivative, PGI2 and PGE1 with their effect on platelet aggregation and bleeding time in rats

ZK 36 374, a new, chemically stable prostacyclin derivative, was compared with PGE1 and PGI2 with respect to its action on platelet aggregation in vitro, on bleeding time and on arterial blood pressure in conscious rats. The time of occlusion of a hole in a polyethylene (PE) tube of an AV-shunt between the left carotid artery and the right jugular vein by a microthrombus was considered as an index of bleeding time. All three substances inhibited the ADP-induced aggregation of human and rat platelets. In human PRP, ZK 36 374 was 17 times more active than PGE1 and 2 - 5 times as potent as PGI2. In contrast, in rat PRP, PGI2 was 9.2 and 3.4 times as potent as PGE1 and ZK 36 374, respectively. Similar differences in potency were found in the in vivo experiments where these substances given by an intravenous infusion to conscious rats prolonged bleeding time and depressed mean arterial pressure in a dose-dependent manner. ZK 36 374 was also orally active. At oral doses of 1, 2 and 3 mg/kg this new compound caused a dose-dependent prolongation of bleeding time and a fall in arterial blood pressure. In conclusion, the results show that ZK 36 374 is an intravenously and orally active prostacyclin derivative which may be of therapeutic value for occlusive peripheral vascular diseases.

Prostaglandin E1 as a hypotensive drug during general anaesthesia

Hypotension induced by prostaglandin E1 (PGE1) infusion (100-150 ng/kg/minute) during halothane anaesthesia to reduce operative blood loss during mastectomy was investigated. PGE1 decreased systolic arterial pressure approximately 34% from pre-administration values. The duration of induced hypotension was about 75 minutes. When the infusion was stopped, blood pressure returned to within 15% of the control with 15 minutes. Heart rate did not change significantly during PGE1 infusion; the pre-ejection period and left ventricular ejection period were shortened. Renal function during the hypotensive period was well maintained. Blood loss during surgery was significantly decreased. These findings suggest that PGE1 can be used safely to control arterial pressure during surgery.

Thrombocyte aggregation in hereditary spherocytosis

Thrombocyte function was studied in seven splenectomized patients and one unsplenectomized patient with hereditary or congenital spherocytosis (HS). Adenosine diphosphate (ADP) concentrations, which trigger the aggregation of control thrombocytes, induced only a release reaction in thrombocytes from six of the HS patients. Collagen-induced thrombocyte aggregation was also diminished in two patients, and epinephrine-induced thrombocyte aggregation in one patient. Two patients whose thrombocytes responded normally to ADP, collagen and epinephrine, were identical twins with spherocytosis of equivocal hereditary. Ristocetin-induced aggregation was normal in all the patients studied. Xanthines (pentoxifylline, theophylline) had no effect on the aggregation of thrombocytes from HS patients or controls. Half-life of thrombocytes was normal in the two splenectomized patients studied. The results demonstrate that not only red cells but also thrombocytes are defective in HS.

Effect of PGE1, PGE2 and PGI2 on ventricular arrhythmias during myocardial infarction in conscious dogs: relation to infarct size

The relation between the effect of vasodilator prostaglandins on ventricular arrhythmias during myocardial infarction and infarct size was studied in conscious dogs. Two infarct-limiting drugs, nitroglycerin and ibuprofen, were also studied for comparison. Infusions were given between 20 and 380 minutes after occlusion of the left circumflex coronary artery: intravenously for saline (N = 27), ibuprofen (N = 14), and nitroglycerin (N = 14); left atrially for PGE1 (N = 11), PGE2 (N = 12) and PGI2 (N = 18). Doses of prostaglandins and nitroglycerin were adjusted to decrease mean arterial pressure by 5%. Pathologic infarct size was measured 2 days post-occlusion. During the infusion period, ventricular fibrillation (VF) deaths were nil with PGI2 (p less than 0.05) and nitroglycerin (p less than 0.1), ventricular premature beats (VPB's) were less (p less than 0.01) with PGI2, PGE2 and nitroglycerin, and collateral blood flow (microspheres) increased with PGE1, PGI2 and nitroglycerin but did not change with saline, PGE2 and ibuprofen. Infarct size, as percent of left ventricle or occluded bed, was less (p less than 0.05) with PGE1, PGI2, nitroglycerin and ibuprofen but similar with PGE2 and saline. Thus, PGE2 diminished VPB's despite no effect on flow or infarct size. In contrast, both PGE1 and PGI2 diminished VPB's, increased flow and decreased infarct size, but PGI2 also reduced VF mortality.

Prostaglandins in myocardial: with emphasis on myocardial preservation

Various therapies during early hours of acute myocardial infarction (AMI) have been suggested to protect ischemic myocardium and reduce infarct size. Despite reports that prostaglandins (PGs) are released during myocardial ischemia, and that prostacyclin (PGI2) and thromboxane A2 (TXA2) have opposing effects on vasomotion and platelet aggregation, the physiologic roles of PGs, PGI2 and TXA2 in AMI have not been clearly defined. However, in pharmacologic doses, experimental evidence suggests that vasodilator PGs might be beneficial, and vasoconstrictor PGs might be deleterious, in AMI. Recent recognition that coronary spasm is frequent in AMI has led to the notion that an increased PGI2/TXA2 ratio might be desirable. Thus, exogenous PGE1, exogenous PGI2 or tis more stable analogs, drugs that stimulate PGI2 release, and inhibitors of TXA2 and harmful PGs are potential agents for protective therapy in AMI.

Influences of prostaglandins on electrophoretic mobility and aggregation of rabbit platelets

Influences of prostaglandin (PG)s on electrophoretic mobilities and aggregation of rabbit platelets were studied. The PGs studied (PGI2, PGE1, PGD2, PGF2 alpha, PGA2 and PGA1) had no effect on platelet electrophoretic mobility. However, both PGE1 and PGI2 in 0.3 and 3.0 muM inhibited ADP-induced aggregation and ADP-induced decrease in the mobility. PGD2 in 0.3 and 3.0, and PGE2 in 30 microM inhibited the aggregation but did not depress the ADP-induced decrease in the mobility. PGF2 alpha, PGA2 and PGA1 had no effect on the decrease in electrophoretic mobility and on the aggregation caused by ADP.

On the multiplicity of platelet prostaglandin receptors. I. Evaluation of competitive antagonism by aggregometry

Methods for the evaluation of competitive interactions at receptors associated with platelet activation and inhibition using aggregometry of human PRP have been developed. The evidence supports the suggestion that PGE1 and PGI2 share a common receptor for inhibition of platelet reactivity, but only a portion (if any) of the aggregation stimulation associated with PGE2 is the result of PGE2 binding (without efficacy) to this receptor. PGE2 (at .3-20 microM) is an effective antagonist of PGE1, PGI2, and PGD2 producing a shift of about one order of magnitude in the IC50-values obtained from complete aggregation inhibition dose response curves. The antagonism of PGD2 inhibition is particularly notable, 80 nM PGE2 levels are detectable. This and other actions of PGE2 indicate another platelet receptor for PGE2. PGE1 acts at both the PGE2 and PGI2 receptor. Other substances showing PGI2-like actions only at high doses (1-30 microM), display additive responses with PGI2 indicative of decreased affinity for the I2/E1 receptor and the absence of PGE2-like aggregation stimulation activity. PGI2 methyl ester has intrinsic inhibitory action not associated with in situ ester hydrolysis. The methyl ester is dissaggregatory showing particular specificity for inhibition of release and second wave aggregation.

A defect in platelet aggregation in Bartter's syndrome

A defect in both the first and second phase of platelet aggregation was found in four subjects with Bartter's syndrome, although template bleeding times were normal. The platelet abnormality was exacerbated by restriction of dietary sodium and lessened by the administration of inhibitors of prostaglandin synthesis. The aggregation defect was not found in other hypokalemic patients or in sodium-restricted normal control subjects. Platelet rich plasma from the subjects with Bartter's syndrome had an abnormally high content of cyclic adenosine 5'-monophosphate (AMP), which may have been responsible for the disordered platelet function. Plasma of these subjects induced both the high content of cyclic AMP and the aggregation defect in normal platelets, whereas suspension of the subjects' platelets in normal plasma improved their aggregation. These findings describe a unique defect of platelet aggregation in Bartter's syndrome, which may be associated with the altered prostaglandin metabolism found in this condition.

13-Azaprostanoic acid: a specific antagonist of the human blood platelet thromboxane/endoperoxide receptor

A newly synthesized 13-aza derivative of prostanoic acid (13-APA) specifically inhibited human platelet aggregation induced by arachidonic acid, prostaglandin H2, or the stable endoperoxide analog (15S)-hydroxy-9 alpha,11 alpha-)epoxymethano)-prosta-5Z,13E-dienoic acid. 13-APA also inhibited [14C]serotonin release in response to arachidonic acid, ADP, or thrombin, but did not inhibit primary aggregation induced by ADP or thrombin. 13-APA completely blocked prostaglandin H2-induced aggregation in indomethacin-treated resuspended platelets but did not inhibit thromboxane synthesis. We therefore conclude that 13-APA acts as a direct antagonist of the platelet thromboxane/endoperoxide receptor.