Electron paramagnetic resonance study on nitric oxide production during brain focal ischemia and reperfusion in the rat

The production of nitric oxide (NO) during brain focal ischemia and reperfusion was measured using diethyldithiocarbamate (DETC)/Fe-citrate, NO trapping reagents, and electron paramagnetic resonance spectroscopy. The NO production is potentiated after 5 min of ischemia, and is continued during 60 min of ischemia. During the reperfusion period after 60 min of ischemia, NO was also produced. However, its production during reperfusion was not observed when the ischemia time was less than 15 min. The NO signal during reperfusion after 60 min of ischemia decreased after 15 min of reperfusion. These results suggest that NO production during ischemia is a physiological reaction for increasing cerebral blood flow, while NO production during reperfusion may be related to cellular damage.

Protective effects of an aged garlic extract on doxorubicin‐induced cardiotoxicity in the mouse

Protective effects of an aged garlic extract on the cardiotoxicity of doxorubicin (DOX) was evaluated using the mouse. DOX (1.5 mg/kg body wt i.p.) was administered three times per week for 40 days. An aged garlic extract, WG-1 (a preserved stock solution; Wakunaga Pharmaceutical) was administered intraperitoneally six times weekly. DOX caused changes in the electrocardiogram. In the control mice, the width of the QRS complex was 20 +/- 2.8 milliseconds, the R-R interval was 130 +/- 2.8 milliseconds, and the P-Q interval was 30 +/- 1.4 milliseconds. In mice treated with DOX for 40 days, the width of the QRS complex was 50 +/- 10 milliseconds (p < 0.05), the R-R interval was 240 +/- 30 milliseconds (p < 0.05), and the P-Q interval was 45 +/- 1.0 milliseconds (p < 0.01). These values were significantly smaller in mice treated with WG-1 + DOX than in mice treated with DOX. The width of the QRS complex was 29.3 +/- 5.8 milliseconds (p < 0.05), the R-R interval was 145.8 +/- 17.9 milliseconds (p < 0.01), and the P-Q interval was 37.8 +/- 3.5 milliseconds (p < 0.05). The lipid peroxidation in the heart homogenates prepared from DOX-treated mice, as measured by thiobarbituric acid-reactive substance (TBARS, nmol malondialdehyde/100 mg protein) was 332.5 +/- 67.0, which was significantly larger than that in the control mice (186.6 +/- 42.2) (p < 0.05). WG-1 decreased the level of TBARS in DOX-treated mice significantly. In the mice treated with WG-1 + DOX, TBARS was 221.3 +/- 31.6, which was significantly smaller than that of DOX-treated mice (p < 0.05). Histological study demonstrated that the heart treated with DOX had vacuolization in muscle cells, disrupted myofibrils, and swollen mitochondria. Mice that received WG-1 + DOX had no significant pathological lesions in the heart.

Beneficial effects of a non-protein diet on renal function of rats exposed to ischemic and nephrotoxic insults

We investigated the effects of a non-protein diet on renal recovery in rats following 45-minute renal ischemia and mercuric chloride (3 mg/kg BW:S.C.) poisoning. The rats were fed a non-protein diet for one week before the renal insults. Renal functions were measured 24 hours after renal ischemia or 6 hours after mercuric chloride administration. In the ischemia investigation, the glomerular filtration rate (GFR), the renal plasma flow rate (RPFR) and the percent fractional sodium excretion (%FENa) of rats fed a regular diet (19.6% protein) were 25 +/- 7 microliters/min/g KW, 0.19 +/- 0.1 ml/min/g KW and 14.8 +/- 2.0, respectively. These values in the rats fed a non-protein diet showed better recovery, returning to a GFR of 114 +/- 32 microliters/min/g KW, an RPFR of 0.37 +/- 0.1 ml/min/g KW, and a %FENa of 2.43 +/- 0.6, respectively (p < 0.05). Furthermore, the seven-day survival rate was improved from 17% in the regular diet group to 100% in the non-protein diet group. In the mercuric chloride investigation, the renal functions in rats on a regular diet were shown by a GFR of 461 +/- 51 microliters/min/g KW, an RPFR of 1.91 +/- 0.2 ml/min/g KW, and a %FENa of 2.22 +/- 0.5. One-week feeding with a non-protein diet ameliorated the decrease in renal function, resulting in a GFR of 604 +/- 84 microliters/min/g KW, an RPFR of 2.15 +/- 0.5 ml/min/g KW, and a %FENa of 2.20 +/- 0.6. Consequently, there was a distinct beneficial effect on the survival of these rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Potentiation of nitric oxide formation following bilateral carotid occlusion and focal cerebral ischemia in the rat: in vivo detection of the nitric oxide radical by electron paramagnetic resonance spin trapping

We have directly demonstrated in vivo that nitric oxide (NO) is produced in the ischemic rat brain. Using diethyldithiocarbamate and Fe as spin-trapping agents, NO spin adducts were detected by cryogenic electron paramagnetic resonance. The cerebral cortex which was exposed to focal ischemia or bilateral carotid artery occlusion generated an increased amount of spin-adducts of NO radicals (g = 2.039, a hyperfine coupling constant aN = 13 gauss). This signal disappeared by the preischemic administration of NG-nitro-L-arginine methylester, a NO synthase inhibitor.

Reversal of chloroquine resistance in murine malaria parasites by prostaglandin derivatives

An oligomeric ester of prostaglandin B2 (OC-5186) was found to reverse chloroquine resistance in the murine malarial parasite Plasmodium berghei. When mice were infected with either chloroquine-sensitive or -resistant P. berghei on day 0 (by intraperitoneal injection of 1 x 10(6) parasitized erythrocytes), they died before day 23. When treated with 15 mg/kg/day of chloroquine for the first four days of infection, all mice infected with the sensitive-strain survived, while all those infected with the resistant strain died before day 23. When OC-5186 (3-12 mg/kg/day) was administered in combination with chloroquine for the first four days, 60% of the animals infected with the resistant strain survived. The differences in the survival rate between the group treated with chloroquine only and the group treated with a combination of drugs (chloroquine plus 3-12 mg/kg/day of OC-5186) were significant. There was also a significant inhibition of parasitemia in the group treated with the combination of drugs. The combinations of chloroquine and a monomer ester of prostaglandin B2 (OC-5181) had some antimalarial activity, but the differences between the chloroquine-treated group and the combination treatment group were not significant in terms of both the parasitemia and the survival rate. Another oligomeric ester of prostaglandin E1 (MR-356) as well as unesterified monomer prostaglandins (PGA2 and PGB2) were ineffective by themselves and in combination with chloroquine.

EPR spin-trapping study of nitric oxide formation during bilateral carotid occlusion in the rat

The formation of nitric oxide (NO) radicals was demonstrated by electron paramagnetic resonance spectroscopy in the rat during varying degrees of brain ischemia. Diethyldithiocarbamate and Fe-citrate were used as in vivo spin-trapping reagents. The signal of NO spin adducts increased in accordance with the degree of ischemic insults. The formation of NO radicals was inhibited by NG-nitro-L-arginine methyl ester.

Inhibition of lipid peroxidation by some dihydropyridine derivatives

The efficacy of dihydropyridine derivatives in inhibiting lipid peroxidation was studied using modified Buege and Aust's method. The method first involves keeping a decapitated rat head at 37 degrees C for 30 min in order to induce global ischemia. Then, the cortex is removed and homogenized, and the homogenate is subsequently exposed to air for 30 min for reoxygenation. Finally, the amount of thiobarbituric acid-reactive substances (TBAR) is measured. With this method, nisoldipine, nimodipine, nitrendipine, nifedipine and nicardipine were all shown to have an antioxidant activity that correlated with their lipophilicity, which was determined by their octanol/water partition coefficients.

Protein-restricted diet prior to renal insult improves the recovery of renal function following ischemia

The effects of a protein-restricted diet on renal recovery following renal ischemia were studied. The renal function was assessed by measuring the inulin clearance (CIN), the p-aminohippurate clearance (CPAH), and the percent fractional sodium excretion (%FENa) 24 h after 45 min renal ischemia. In rats fed with a regular diet (containing 19.6% protein), CIN was 10.0 +/- 2.2 microL/min/100 g body weight (BW), CPAH 0.08 +/- 0.02 mL/min/100 g BW, and %FENa 14.8 +/- 2.0, 24 h after renal ischemia. In contrast, feeding rats with a no-protein diet (0% protein) for 1 week prior to the ischemic insult significantly improved renal recovery (CIN 48.0 +/- 9.3 microL/min/100 g BW, CPAH 0.16 +/- 0.04 mL/min/100 g BW, and %FENa 2.43 +/- 0.58). Feeding rats with a no-protein diet for 3 weeks prior to ischemic insult further improved the renal recovery (CIN 113 +/- 30 microL/min/100 g BW, CPAH 0.47 +/- 0.17 mL/min/100 g BW, and %FENa 1.55 +/- 0.29). When rats fed with a regular diet were exposed to 45 min of ischemia, the survival rate on day 7 was 16.7%. In rats fed with the no-protein diet for 1 week and for 3 weeks, the 7-day survival rate was 100% in each case. The survival rate of rats fed for 3 days instead of 7 days with the no-protein diet was 87.5%. When a no-protein feeding was shortened to 1 day, no beneficial effects were observed and survival rate was 14.3%. (ABSTRACT TRUNCATED AT 250 WORDS)

Protective effects of a prostaglandin E1 oligomer on taurocholate-induced rat pancreatitis

Effects of prostaglandin E (PGE) on acute pancreatitis have been controversial. This study shows the effects of PGE1 oligomer, MR-356, on trypsin-taurocholate-induced acute pancreatitis in rats. Divided intraperitoneal doses of 0.6 mg/rat were administered, which increased 24 h survival rates when the oligomer was given both at 1 h before and after (group A) and immediately and 3 h after (group B) induction of pancreatitis. In group A MR-356 significantly improved the survival rates at 18 h (94 vs 61%, P < 0.05) and 24 h (68 vs 33%, P < 0.05) when compared with controls. MR-356 improved the survival rates dose-dependently up to 0.6 mg/rat when given by the same protocol of group A. In group B MR-356 also improved the survival rate (72 vs 39%, P < 0.05) only at 24 h, while other parameters failed to improve. The present results suggest that the PGE1 oligomer may play a beneficial role in bile-induced pancreatitis, probably through its proposed effects of stabilization of lysosomal membranes, maintenance of microcirculation and inhibition of protease in the pancreas.

Free radical formation during splanchnic artery occlusion shock

Free radical (FR) formation in the rat intestinal lumen was measured using the spin-trapping technique and electron paramagnetic resonance spectroscopy. Intestinal ischemia was produced by occluding the celiac and the superior mesenteric arteries for 30 min followed by reperfusion. The lumen was filled with a solution of PBN (N-tert-butyl-alpha-phenyl-nitrone) and the intestine was squeezed to enhance the interaction between the PBN solution and the intestinal mucosal cells. Free radicals were produced upon reperfusion, with peaks at 5 and 90 min. Post-ischemic treatment with superoxide dismutase (20 mg.kg(-1)) inhibited the increase of FR production during the second peak by 36%. In a single study in a group of leucocytopenic rats (WBC < 1500/mm(3)), the increase of FR production during the second peak was decreased by 80%. However, these treatments did not inhibit the FR production during the first peak in either group. In contrast, pretreatment with allopurinol (40 and 100 mg.kg(-1) injection at 24 and 3 hours before ischemia, respectively) inhibited the FR production during the first peak by 76%, but did not inhibit during the second peak. The changes in lipid peroxidation in the intestinal mucosa, specific gravity of the intestine and in the hematocrit were correlated to the FR production in the second peak. These results suggest that a major cause of tissue injury after reperfusion in the ischemic intestine may largely be produced by neutrophils.

Protective effect of a prostaglandin oligomer on liver mitochondria in situ: time-shared measurements of fluorescence and reflectance in the cold-preserved rat liver

The protective effect of a new oligomeric derivative of prostaglandin B2, known as OC-5186, was evaluated using time-sharing spectrofluorometry in the cold-preserved rat liver. Experiments were divided into three groups: in group A, a 5000 ng dose of OC-5186 was administered via the peripheral vein, 1000 ng via the portal vein, and 200 ng/ml in University of Wisconsin (UW) solution; in group B, the OC-5186 dosage was ten times greater than that in group A; in group C (control group), liver procurement and storage were performed without OC-5186. At 0, 12, and 24 h after cold preservation at 4 degrees C, the liver was perfused for 30 min at 12 degrees C with oxygenized Krebs-Henseleit solution, after which the perfusate was switched to deoxygenized Krebs-Henseleit solution. Time sharing spectrofluorometry was used to follow NADH fluorescence at 450 nm with a 360-nm excitation wavelength, as well as the reflectance of cytochrome aa3 with 605 minus 620 nm from oxidation to reduction. Rate constants of NADH fluorescence and cytochrome aa3 reflectance were used as indices of integrity of the mitochondrial respiratory chain. In group C, the rate constant of NADH fluorescence decreased significantly (P < 0.05) from the control value of 8.31 +/- 0.21 x 10(-3) (sec-1) to 4.97 +/- 0.15 x 10(-3) and 5.58 +/- 0.16 x 10(-3) (mean +/- SEM) at 12 and 24 h after cold preservation, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of lipid peroxidation by prostaglandin oligomeric derivatives

The inhibition of lipid peroxidation by oligomeric derivatives synthesized from prostaglandin E1 (PGE1) and PGB2 was studied using two rat models. In an in vitro model, the brain was exposed to decapitation-ischemia, the cortex was removed and homogenized, and the formation of thiobarbituric acid reactive substances (TBAR) was measured after exposing the homogenate to in vitro reoxygenation either in the presence or absence of oligomers. It was found that these oligomers could inhibit lipid peroxidation, and that their activities were higher than that of superoxide dismutase (SOD). In an in vivo administration model, either the oligomer or the vehicle was injected i.p. 30 min before decapitation. The brain was exposed to decapitation-ischemia, the cortex was homogenized and exposed to 'in vitro' reoxygenation, after which TBAR value was determined. Ester-type compounds had a greater activity than free-acid type compounds in inhibiting lipid peroxidation. A possible mechanism of the protective effect of these oligomers in ischemia/reperfusion injury may be to scavenge oxygen free radicals.

Inhibitory effect of prostaglandin oligomeric derivatives on 9,10-dimethyl-1,2-benzanthracene-induced hamster lingual carcinomas

The inhibitory effects of prostaglandin oligomeric derivatives OC-3186 and OC-5186 were examined in hamster lingual carcinoma induced by 9,10-dimethyl-1,2-benzanthracene (DMBA). These compounds caused a regression of 40-90% in the size of lingual carcinomas in the hamster within several days after systemic or local administration.

Biologically significant physico-chemical properties of antioxidative prostaglandin derivatives

A monomeric derivative and several oligomeric derivatives were synthesized from prostaglandin B2. Their lipid solubility was studied by measuring their octanol-water partition coefficients. With EPR spectroscopy, the oligomeric derivatives were shown to have g = 2 signal, indicating these compounds have intrinsic free radicals. Measuring the rate of adenochrome formation, it was shown that these derivatives could scavenge superoxide anions. Using a spin-trapping technique employing DMPO, we found that these oligomers could also scavenge hydroxyl radicals. The calcium chelating activity of these compounds were also studied. In an in vitro rat model, these compounds inhibited lipid peroxidation as measured by the production of thiobarbituric acid reacting substances. Other prostaglandin oligomeric derivatives synthesized from PGE1 were also studied, and their properties were compared with these new compounds. Results suggest that both the water solubility and the chelating activity for calcium ions may not be related to their protective effects in ischemic or traumatic injury.

Chronic alcoholism impedes the recovery of renal function following renal ischemia

The recovery of renal function following renal ischemia was studied using rats fed for 1-, 3-, and 5-week periods with an alcoholic diet (ethanol provided 36% of total calories). Renal ischemia was produced by clamping the renal artery and vein for 20 min. Renal function was determined 24 hr after the ischemia. In the absence of ischemic insult, the renal function of rats fed with an alcoholic diet for 1, 3, and 5 weeks was not significantly different from those of nonalcoholic rats. In nonalcoholic rats, renal function (24 hr postischemia) were: glomerular filtration rate (GFR) 430.4 +/- 29.6 microliters/min/g KW (kidney weight), renal plasma flow rate (RPFR) 1.4 +/- 0.17 ml/min/g KW, and fractional sodium excretion (FENa) 2.0 +/- 0.04% (mean +/- SE). Postischemic renal function of rats on 1- and 3-week alcoholic diets were essentially the same as that of the control rats. However, the 24-hr postischemic renal function of 5-week alcoholic diet rats was significantly depressed. The values were only 117.2 +/- 35.2 microliters/min/g KW (p less than 0.05) for GFR, 0.31 +/- 0.12 ml/min/g KW (p less than 0.05) for RPFR, and 7.46 +/- 3.59% for FENa. The present results demonstrate that the rat kidney subjected to prolonged alcohol ingestion was more susceptible to renal insult than a nonalcoholic kidney.

Relationship between free radical production and lipid peroxidation during ischemia-reperfusion injury in the rat brain

Forebrain ischemia was produced in the rat by bilateral occlusion of the common carotid arteries combined with hemorrhagic hypotension (30 mmHg). The whole cerebral cortex was homogenized in the presence of the spin trap agent N-tert-butyl-alpha-phenyl-nitrone, followed by a Folch extract. Spin-adducts were detected using electron spin resonance spectroscopy. The lipid peroxidation was estimated from both the amount of thiobarbituric acid reactive substance and the formation of conjugated diene. After 10 or 20 min of ischemia, reperfusion was initiated which induced an abrupt burst of free radical formation. The formation peaked at 5 min, and the peak value increased with the ischemia time. The degree of lipid peroxidation, which was measured after 20 min of reperfusion, also increased with the ischemia time. The results suggest that the lipid peroxidation may be the direct consequence of the action of free radicals formed during ischemia and reperfusion periods.

[31P]MRS study of the protective effects of prostaglandin oligomers on forebrain ischemia in rats

Two ester-type prostaglandin oligomeric compounds were synthesized, one from prostaglandin E1 (termed MR-356) and the other from prostaglandin B2 (termed OC-5186). Using in vivo [31P]MRS, the protective effects of these oligomers on forebrain ischemia (15 min) were evaluated in a rat model. Forebrain ischemia caused a decrease in intracellular high energy phosphates and intracellular pH (pHi) in the control and compounds-treated groups, but changes of these values in the OC-5186-treated group were significantly smaller than those in the control group. Moreover, the cerebral energy metabolism of the OC-5186-treated group returned to the preischemia level more rapidly than in the control group after forebrain ischemia. MR-356 had some effects, but the differences were not significant.

Why does halothane relax cardiac muscle but contract malignant hyperthermic skeletal muscle?

We have studied the question of the possible role of sarcoplasmic reticulum (SR) in the interaction of volatile anesthetics (such as halothane, enflurane and isoflurane) with muscle. We used two cardiac muscle models, i.e., isolated rat myocytes and Langendorff perfused rat hearts. We compared the results with those for skeletal muscle SR from rabbits, rats and pigs susceptible to malignant hyperthermia (MH). In both skeletal and cardiac muscle SR, volatile anesthetics enhanced the calcium release from the SR. In cardiac muscle, these agents are known to decrease contractility (negative inotropism). We found that caffeine, a well-known agent which releases calcium from the SR, also had a negative inotropic effect in cardiac muscle, raising the possibility of an unexpected link between the potentiation of calcium release and mechanism underlying the observed negative inotropism. Current understanding of anesthetic mechanisms does not include this possibility. We further found that both volatile anesthetics and caffeine decrease the content of calcium in the SR, suggesting that the increase of calcium permeability results in the decrease of calcium ions in the SR which are available for excitation-contraction (E-C) coupling. In MH-susceptible skeletal muscle, a similar increase in calcium permeability does not cause a decrease of contractility, but rather may contribute to a fatal syndrome of temperature increase provoked by abnormal contracture. This difference may be because in skeletal myoplasm calcium ions recycle internally, while in the cardiac muscle cell they are in dynamic equilibrium with extracellular calcium ions.

Protective effect of a new anti-oxidant on the rat brain exposed to ischemia-reperfusion injury: inhibition of free radical formation and lipid peroxidation

A new oligomeric derivative was synthesized from prostaglandin B2 and ascorbic acid, and its effect on rat brain ischemia-reperfusion injury was studied. Brain ischemia was produced in the rat by the combination of bilateral common carotid artery occlusion and hemorrhagic hypotension (30 mmHg, 20 min). The cerebral cortex was homogenized in the presence of the spin trap agent, N-tert-butyl-alpha-phenyl-nitrone (PBN). Spin-adducts were detected using an electron spin resonance spectrometer (EPR). Lipid peroxidation was estimated from the amounts of both thiobarbituric acid reactive substances (TBAR) and conjugated diene. In control experiments, reperfusion induced a burst of free radical formation which peaked at 5 min reperfusion time (238 +/- 41%). Lipid peroxidation increased significantly after 20 min of reperfusion (TBAR, 161 +/- 50%; conjugated diene, 160 +/- 29%). When the oligomeric derivative was administered (9 mg/kg i.p. 30 min before ischemic insult), it significantly reduced both spin adduct formation (103 +/- 13%) and lipid peroxidation (TBAR, 109 +/- 14%; conjugated diene, 97 +/- 33%).

Studies on the permeability of potassium ions across the dura and arachnoid mater of the rat spinal cord

A combined impounder-surface K+ electrode was developed to measure change in K+ ion concentration of the cerebrospinal fluid (CSF) across the dura and arachnoid maters. To determine whether K+ permeability of the rat dura and arachnoid maters is due to an intrinsic permeability, a study was conducted using an atraumatic laminectomy model. Dorsal laminectomy was performed at T7-8, T12, and L1. Artificial CSF containing 4.2 mM, 24.2 mM, or 54.2 mM of K+ was administered by anterograde subdural infusion into the subarachnoid space from the proximal laminectomy site (T7-8), with effluent overflow at the distal laminectomy site (L1). K+ concentration on the dorsal aspect of the central laminectomy site (T12) was measured. It was found that changes in K+ concentrations of the infused solution were detected by the epidural surface electrode. This suggests that the intact rat spinal cord dura and arachnoid maters may be permeable to K+ in this laminectomy model. This study supports the use of the combined impounder-K+ electrode for measuring changes in K+ ion concentration of the CSF that can result from spinal cord trauma and ischemia.

Pharmacologic protection of perfused rat heart against global ischemia

Using a Langendorff rat heart model, studies were performed on the effects of three drugs in protecting the heart against global ischemia. The drugs used were: (a) MR-256, a prostaglandin oligomeric derivative, which is a calcium chelating agent and at the same time, is an inhibitor of phospholipase A2 activity, (b) chlorpromazine which is not a calcium chelator, but is a calmodulin antagonist and is an inhibitor of phospholipase A2 activity, and (c) BAPTA/AM, a calcium chelating agent, but which is not an inhibitor of phospholipase A2 activity. The perfused heart was exposed to 15 minutes of global ischemia. In control experiments (no drug), the ventricular pressure recovered to 26.4 +/- 6.7% (n = 22) of the original level. With pretreatment of (a) MR-256 (b) chlorpromazine, and (c) BAPTA/AM, maximum recoveries were 0.5 +/- 6.7% (n = 5), 88.7 +/- 8.5% (n = 5), 45.3 +/- 26.6% (n = 5), respectively. MR-256 and chlorpromazine were found to react with free radicals. The modes of action of these three different types of drugs are discussed.

Effects of membrane acting-drugs on plasmodium species and sickle cell erythrocytes

The effects of several membrane-acting drugs on malaria and sickle cell anemia was studied. In the initial experiments, propranolol and W-7 were shown to increase red cell density. In vitro, these drugs inhibited the growth of P. falciparum. However, in vivo experiments using the murine malarial parasite, P. vinckei, demonstrated little, if any, anti-parasite activity with the doses of drugs employed. Subsequently, prostaglandin oligomeric derivatives were found to inhibit the growth of P. falciparum in vitro and P. vinckei in vivo. Since prostaglandin oligomers inhibited the formation of dense, dehydrated cells (irreversible sickle cells), they may also have therapeutic efficacy in sickle cell anemia.

Prostaglandin oligomeric derivatives inhibit in vitro formation of dehydrated cells from sickle red cells

Two types of oligomeric derivatives of prostaglandin E1 were synthesized, a free-acid type and a lipophilic ester type. Neither compound inhibited sickling of red blood cells from sickle cell anaemia patients. However, both were found to inhibit the in vitro formation of dehydrated, dense cells (DC) caused by repeated cycles of sickling and unsickling of sickle cells. Both inhibited the formation of DC in a dose-related manner, but the ester type compound was more effective than the acid-type compound. Concentrations at which these compounds inhibit the DC formation by 50% were 5.2 microM and 40 microM for ester and free-acid compounds, respectively. A possible inhibition mechanism is discussed.

Inhibition of ischemic brain edema formation by post-ischemic administration of a prostaglandin oligomer

We studied the efficacy of an oligomeric derivative of prostaglandin E1 in protecting the rat brain against focal ischemia. The degree of ischemic damage was evaluated from three parameters, namely, the degree of edema formation, reduction of motor performance, and memory disturbance as measured by a passive avoidance test. The pre-ischemic administration of the drug (6 mg/kg i.p.) had some effects, but the differences were not significant. The post-ischemic administration (6 mg/kg i.p.) produced significant improvement in all three parameters. The increase of water content of the ischemic hemisphere was reduced (p less than 0.05); the total motor score was improved (p less than 0.01); and the memory disturbance as estimated by the passive avoidance test was reduced (p less than 0.01). A possible mechanism of protection is discussed.

Studies of the cation binding properties of an oligomeric derivative of prostaglandin B1

The ionophoretic activity of PGBx, an oligomeric mixture synthesized from 15-dehydro PGB1, with different cations was measured using arsenazo III-entrapped liposomes. The order of ionophoretic activity was Zn2+ greater than Co2+ greater than Mn2+ greater than Cu2+ greater than Ca2+ greater than Ba2+ greater than Sr2+ greater than Mg2+. The intrinsic fluorescence of PGBx was quenched by the binding of divalent cations as well as by La3+ and H+. Quenching by K+ and Na+ was minimal. The order of quenching strength of divalent cations was Zn2+ greater than Co2+ greater than Cu2+ = Mn2+ greater than Ca2+ greater than Ba2+ greater than Sr2+ greater than Mg2+. Binding affinities of these cations determined by a murexide indicator method were in good agreement with that determined by the fluorescence quenching reaction. The cation binding affinity of PGBx in aqueous solutions correlates with the ionophoretic activity in liposomes. The binding affinity for K+ was estimated from the inhibition by K+ of Ca2+ binding by PGBx. Although PGBx has a lower selectivity for divalent cation binding than the ionophore A23187, the characteristics of the binding affinity of these two compounds for various ions were similar. The pK of PGBx as determined by fluorescence quenching was 6.7. The molecular weight of the divalent cation binding unit was estimated to be about 680, with each PGBx molecule having three such binding sites. The binding of Ca2+ to such a site is one-to-one.