Jadwiga Robak

The effect of 4-acetamidophenol on prostaglandin synthetase activity in bovine and ram seminal vesicle microsomes

Abstract The effect of paracetamol (4-acetamidophenol) on PG synthetase activity was tested in bull (BSVM) and ram (RSVM) seminal vesicle microsomes. In the presence of glutathione (165 μM) and hydroquinone (45 μM) in BSVM paracetamol (up to 67 μM) had no effect or inhibited ( IC 50 = 1500 μ M ) the enzymic activity. In the absence of cofactors paracetamol (67–667 μM) stimulated the generation of PGs in BSVM. Also in RSVM paracetamol (33–333 μM) stimulated PG and malondialdehyde generation as well as oxygen consumption, provided that the exogenous cofactors were omitted from the incubation mixture. Hydroquinone (150 μM) was able to abolish the stimulatory effect of paracetamol on the enzymic activity. We conclude that paracetamol can replace hydroquinone and other cofactors for cyclo-oxygenation of arachidonic acid in BSVM and RSVM. The inhibitory effect of paracetamol on PG synthetase activity occurs only in the abundance of exogenous cofactors in the microsomal preparation.

Thrombolytic action of ticlopidine: possible mechanisms

Ticlopidine (Ticlide), an anti-platelet drug with a broad scope of clinical applications, is claimed to be an antagonist of adenosine diphosphate on platelet receptors. In vitro this antagonism cannot be demonstrated. Ex vivo it is detectable many hours after oral administration of the drug, perhaps subsequently to its biotransformation to an unknown metabolite. Here, we report for the first time that in patients with peripheral arterial disease and in cats with extracorporal circulation ticlopidine evokes instantaneous thrombolytic or fibrinolytic effects which are not associated with inhibition of platelet aggregation. Shortening of euglobulin clot lysis time and increase in plasma levels of tissue plasminogen activator were observed 1-2 h after oral ingestion of ticlopidine at a single dose of 500 mg. In cats ticlopidine produced instantaneous anti-thrombotic and thrombolytic effects at doses of 0.3-1 mg/kg and 10-15 mg/kg i.v., respectively. Thrombolysis by ticlopidine (10 mg/kg i.v.) was comparable to that by prostacyclin at a dose of 0.3 microgram/kg i.v. Ticlopidine at a concentration of 100 microM increased endothelial thromboresistance in vitro. The drug did not inhibit the activity of cyclooxygenase-1 or 12-lipoxygenase while it inhibited lipid autooxidation (IC50 = 18 microM) in rat liver microsomes. Our data point to a possibility that the therapeutic efficacy of ticlopidine might be associated not only with its delayed anti-platelet effects but also with its immediate thrombolytic action which is likely to be mediated by endothelial prostacyclin and tissue plasminogen activator rather than by platelet mechanisms.

Relationship between lipid peroxidation and prostaglandin generation in rabbit tissues

Abstract Lipid peroxides are formed non-specifically from unsaturated lipids and specifically in the course of prostaglandin biosynthesis. Both kinds of peroxidation were found to be interrelated in homogenates of the renal medulla, lungs and spleen of rabbits but not in homogenates of the renal cortex and brain. Lipid peroxidation was increased by ascorbic acid and ferrous ions, especially in the renal cortex, brain and renal medulla homogenates. Arachidonic, but not oleic, acids increased lipid peroxidation in the renal medulla, but this augmentation is inhibited by indomethacin. Arachidonic, as well as oleic, myristic and linolenic acids, markedly depressed lipid peroxidation in the renal cortex. It is concluded that lipid peroxidation in the renal medulla is mainly specific and in the renal cortex mainly non-specific.

The influence of saturated fatty acids on prostaglandin synthetase activity

Abstract Saturated fatty acids (C10, C12, C14, C16 and C18) as well as lauryl sulphate inhibit the microsomal prostaglandin synthetase of bovine seminal vesicles (BSVM). The most potent inhibitors are lauryl sulphate, lauric and myristic acids ( ic 50 = 250 μ M ). The last two acids are strong ligands to hydrophobic sites of albumin. Indomethacin is also strongly bound to the hydrophobic sites of albumin; however, indomethacin inhibits the generation of prostaglandins at a concentration approximately 2500 times lower than the most active fatty acid inhibitor. The inhibitory action of fatty acids and indomethacin on prostaglandin synthetase activity has been measured by estimation of either PGE2 or malondialdehyde, which are generated from arachidonic acid by BSVM. The former procedure is more reliable and reproducible than the latter.

Adjuvant-induced and carrageenin-induced inflammation and lipid peroxidation in rat liver, spleen and lungs

Abstract Lipid peroxidation in homogenates of spleen, liver and lungs of rats was tested by the thiobarbituric acid method in the presence or in the absence of exogenous ferrous ions and ascorbic acid. A mild increase of stimulated lipid peroxidation was observed in liver of rats with carrageenin hind paw edema only 3 hr after the injection. In the Freunds adjuvant treated rats a dramatic suppresion of liver but not spleen and lungs lipid peroxidation was found at days 1–21 after the injection. This phenomenon was not correlated with the observed splenohepatomegaly. It is probably the result of the damage of an enzymic or non-enzymic mechanism which induces lipid peroxidation in the liver.

The influence of some 3-amino-2-pyrazoline derivatives on cyclooxygenase and lipoxidase activities

The influence of 3-amino-1-[m-(trifluoromethyl)-phenyl]-2-pyrazoline (BW 755C), 1-(3,3-diphenylpropyl)-3-amino-5-methyl-2-pyrazoline (KD 785) and 1-(3,3-diphenylpropyl)-3-amino-2-pyrazoline (KD 679) on cyclooxygenase and lipoxidase activities has been studied. All three compounds inhibited soybean and platelet lipoxidase activity. BW 755C was a much stronger inhibitor than KD compounds. The tested compounds stimulated oxygen consumption by cyclooxygenase from ram seminal vesicle microsomes in the presence of 100 microM of arachidonic acid in the range of concentrations between 30 and 300 microM and increased PGE2 generation in these experimental conditions. Radiochemical studies showed that BW 755C had been a stimulator of cyclooxygenase in higher (100 microM) substrate concentrations but, in agreement with a previous report it acted as an inhibitor of this enzyme when substrate concentration was 1.6 microM. Probably this component acted as a free radical scavenger.

Mesoionic Oxatriazoles (MOTA): NO-Donating Characteristics and Pharmacology

Biological role of nitric oxide (NO), functioning of isoforms of NO synthetases (NOS) and pharmacology of principle NO-donors were reviewed. NO donating characteristics and pharmacology of 23 mesoionic oxatriazoles (MOTA) were compared with those of 5-morpholinosydnonimine (SIN-1), S-nitroso-N-acetylpenicillamine (SNAP), sodium nitroprusside (NaNP) and glyceryl trinitrate (GTN). It is concluded that in vitro NO donating profile of MOTA hardly can be used as a predicting measure for their pharmacological activities either in vitro or in vivo. If anything, fast NO releasers seem to be stronger vasorelaxants than MOTA with slow NO releasing properties. Still, among representatives of this last category of MOTA one may find efficient antithrombotic and thrombolytic agents. For instance, MOTA 5-oxides were more potent thrombolytics than SIN-1, SNAP or NaNP. Also MOTA with potent anti-platelet action in vitro seem to be potent relaxants of tracheal strips. In summary, by manipulating the chemical structures of MOTA one may obtain relative selectivity towards vasorelaxant, anti-platelet, thrombolytic or tracheorelaxant properties. Thus different categories of MOTA might be designed with a hope of achieving hypotensive, antithrombotic, thrombolytic or anti-asthmatic drugs.

The influence of propranolol, inpea, iproveratril and some 1-naphthylethylamine derivatives on the myocardial phosphorylase activity☆☆☆

Abstract The antiarrhythmic or negative inotropic and chronotropic response to drugs may be the result of β-adrenergic blockade or the result of the quinidine-like action. The influence of the cardioactive drugs on the isoprenaline-induced phosphorylase activity in the cardiac muscle is decisive in this respect. The influence of propranolol, INPEA, iproveratril and two 1-naphthylethylamine derivatives on the isoprenaline induced phosphorylase activity was studied. Rat hearts were perfused by the method of Langendorff during 20 min. The compounds were infused alone in the range of 0.5–500 μg doses and also 2 min after 0.1 μg isoprenaline (IP) was injected into the perfusion system. Samples of the muscle were taken 30 sec afterwards and the phosphorylase activity was determined. Control hearts were treated with IP alone. IP increased significantly the phosphorylase activity in cardiac muscle as compared with the control. Propanolol completely prevented the effect of IP on metabolism and reduced the mechanical effect of IP. d (—)N- isopropyl -p- nitrophenyl-ethanolamine d(—) INPEA (5 μ g ) and l(+) INPEA (50 μg and 500 μg) were ineffective against the IP-induced stimulation of the heart. d (—)INPEA at 50 and 500 μg reduced the effect of IP on phosphorylase activity and blocked completely the pharmacodynamical action of IP on the heart muscle. α-isopropyl-α-[(N-methyl-N-homoveratryl)-α-aminopropyl]-3,4-dimethoxyphenylace-tonitrile (Iproveratril) at 0.5 and 2.5 μg depressed the cardiac activity but not the mechanical or metabolic effects of IP. N-isopropyl-α-methyl-β-1-naphthylethylamine (S-870) (5 μg) and N-propyl-α-methyl-β-1-naphthylethylamine (S-931) (5 μg) did not influence the phosphorylase activity in the heart or the effects of IP.

Binding of the membrane active drugs to bovine serum albumin and human erythrocyte membranes

Abstract The binding of 14 non-steroidal anti-inflammatory drugs, 3 beta-adrenolytics and 8 miscellaneous drugs to bovine serum albumin (BSA) and human erythrocyte membranes (HEM) was investigated by using 8-anilino-1-naphthalene sulphonate (ANS) as a fluorescent probe. Anionic drugs which are known to protect proteins against denaturation strongly quench the fluorescence of the ANS-BSA complex, and to a lesser extent the fluorescence of the ANS-HEM complex. None of cationic or nonionic drugs tested so far are able to displace ANS from the ANS-BSA complex but some of them, known as “membrane active” agents, intensify the fluorescence of the ANS—HEM complex. Within the group of nonsteroidal anti-inflammatory drugs only those drugs which are inhibitors of prostaglandin biosynthesis have been found to quench the fluorescence of the complexes of ANS with BSA or HEM. Both anionic and cationic “membrane active” drugs protect erythrocytes against hypotonic hemolysis but the mechanisms of this effect are different.

Influence of INPEA, pindolol and propranolol on the chronotropic and metabolic responses to β-adrenergic stimulation in intact rats

Abstract A study was made of the effect of isoprenaline given intraperitoneally to rats on the chronotropic effect and the activation of myocardial phosphorylase. Pretreatment with three β-blocking agents: pindolol, propranolol and INPEA was carried out to separate metabolic and chronotropic effects of isoprenaline on heart. Isoprenaline at 0.01–40 mg/kg augmented heart rate, but the activation of phosphorylase started only from the dose of 0.02 mg/kg. Metabolic effect of isoprenaline reached the maximum at a lower dose (0.1 mg/kg) than chronotropic effect of isoprenaline did (1 mg/kg). Pindolol at 0.03 mg/kg, propranolol in doses 0.5–5 mg/kg and INPEA at a dose of 50 mg/kg slowed heart rate but did not influence phosphorylase activity. INPEA in doses 0.5–5 mg/kg, accelerated heart rate, but did not activate myocardial phosphorylase. β-Blocking potency of all three drugs was nearly the same with respect to metabolic and chronotropic response to isoprenaline, but only when measured at the level of 50 per cent of inhibition. 1050 were: pindolol —0.006 mg/kg, propranolol —0.33 mg/kg and INPEA —2.8 mg/kg, however distinct differences between metabolic and chronotropic blockade in other doses of propranolol and INPEA were found. Linear dose dependent β-adrenergic blockade was induced with respect to metabolic and chronotropic effects by pindolol, with respect to chronotropic effect by propranolol and in respect to metabolic effect by INPEA. The blockade of metabolic effect by propranolol and the blockade of chronotropic effect by INPEA occurred abruptly from the zero level to maximal level when the dosage of these drugs was doubled.