Effects of arachidonic acid and bradykinin on the coronary flow, release of PGI2 and cardiac functions in the perfused guinea-pig heart

The contribution of prostacyclin (PGI2) to the coronary vasodilating action of arachidonic acid (AA) and bradykinin (BK) was examined in isolated perfused guinea-pig hearts. The injection of Aa (100 to 1,000 ng) and BK (1 to 100 ng) into the heart resulted in a dose-dependent increase in the total amount of coronary flow and a release of 6-keto-prostaglandin F1alpha, a stable metabolite of PGI2. Both AA and BK showed weak positive chronotropic effects. In addition, higher doses (300 and 1,000 ng) of AA caused a transient reduction in the coronary flow rate, left ventricular systolic pressure, and left ventricular dp/dt. The changes in coronary flow, release of PGI2, and all cardiodynamic parameters induced by AA were abolished by pretreatment of the preparation with diclofenac-Na. On the other hand, the BK-induced increase in coronary flow rate was only partially reduced by diclofenac-Na when the release of 6-keto-prostaglandin F1alpha was completely inhibited. It is concluded that in isolated perfused guinea-pig hearts, BK has both PGI2-independent and PGI-2-dependent coronary vasodilating actions; the latter action is less than 25%, and the coronary vasodilating action of AA is mainly mediated via PGI2.

Morphological changes of isolated rat hepatocytes induced by imipramine

Effect of imipramine on freshly isolated rat hepatocytes was investigated by scanning and transmission electron microscopy. Soon after the treatment of the cell with imipramine, marked changes in plasma membrane and mitochondria were found. Amitriptyrine, a structurally related drug, produced similar changes in the hepatocytes. On the other hand, Triton X-100, a nonionic surfactant, damaged the cell surface but little influence the features of the organelles.

[Determination of bromine contents in the blood and hair of workers exposed to methyl bromide by radioactivation analysis method]

The bromine contained in blood and hair samples obtained from workers exposed to methyl bromide was analyzed by non-destructive activation analysis. The samples were irradiated for 1 min in pneumatic irradiation facility of Kyoto University research reactor with an estimated thermal neutron flux density at 2 X 10(13)n X cm-2 X sec-1. The irradiation was counted with Ge(Li) detector. The duration of measurement of radionuclide bromine in blood and hair was 200 sec within 2-10 min after irradiation. The bromine content of serum sample obtained from a worker suspected of methyl bromide poisoning was found to be 412 micrograms/g on 13 days apart from exposure to methyl bromide. The biological half-life of bromine in this case was found to be about 16 days. Then bromine contents in serum and hair samples obtained from workers exposed to methyl bromide were found to be 1.7 and 2.6 times higher respectively than those of nonexposed workers. Any correlations of bromine contents were not observed between serum and hair samples obtained from workers exposed to methyl bromide, nor between bromine amount in the serum of workers exposed to methyl bromide, and the terms exposed to it, but statistically significant positive correlation was observed between bromine amount in the hair of workers exposed to methyl bromide and the terms exposed to it.

Hepatic bile acid elution by albumin and bile acid content in isolated rat hepatocytes

Bile acid contents were determined for isolated rat hepatocytes. During the course of isolating the hepatocytes, perfusion of rat liver with buffer containing 2% albumin eluted a significant amount of bile acids. The elution was proportional to the volume of the buffer and attributable to albumin in the buffer. The isolated hepatocytes prepared by perfusion with 0.1% albumin buffer, which eluted a negligible amount of bile acids, contained 95 +/- 12 micrograms/10(8) cells of bile acids. The major bile acids were cholic acid (22%), beta-muricholic acid (34%) and hyodeoxycholic acid (10%). Levels of the other bile acids were less than 3%. Peak 8, unidentified but presumed to be a trihydroxycholanoic acid, accounted for 19%.

Coronary circulatory failure and thromboxane A2 release during coronary occlusion and reperfusion in anaesthetised dogs

Attempts were made to demonstrate release of vasoactive substances from the heart during coronary occlusion (for 60 min) and reperfusion (for 60 min), and to clarify the pathophysiological significance of them. Vasoactive substances were detected by superfusion of rabbit aortic and dog coronary arterial strips with great coronary venous blood. Plasma thromboxane (TX) B2 was radioimmunologically assayed. Gradually developing, sustained contraction of both vascular strips was noted during coronary occlusion and reperfusion, while a transient contraction in rabbit aortic and relaxation in dog coronary arterial strips were seen immediately after reperfusion. The TXB2 released into the great coronary venous blood significantly increased during occlusion and reperfusion. Indomethacin treatment of the dog abolished the sustained contraction of both vascular strips and TXB2 release. The transient contraction of rabbit aorta after reperfusion was inhibited by phenoxybenzamine. Reactive hyperaemia following a 60 min occlusion was significantly depressed, as compared with that following 30 s to 30 min occlusion, and the depression was alleviated by indomethacin and imidazole. These results suggest that catecholamine(s) and TXA2 are released during coronary occlusion and reperfusion, and that the latter might be responsible for the coronary circulatory failure during reperfusion of irreversibly damaged myocardium.

Biochemical evidence for the coexistence of monomorphic and polymorphic N-acetyltransferase activities on a common protein in rabbit liver

New Zealand White rabbits were classified as rapid or slow acetylators by measuring the N-acetylation half-life of i.v. administered sulfadiazine, by pedigree analysis and by determination of liver N-acetyltransferase (NAT) activity in vitro. Slow acetylator rabbits were found to have significantly lower levels of p-aminobenzoic acid NAT activity in vitro than did rapid acetylator rabbits, demonstrating genetic covariation of p-aminobenzoic acid (monomorphic) and isoniazid (polymorphic) NAT activity. Monomorphic and polymorphic NAT activities could not be separated by two extensive purification procedures involving sequential centrifugation, fractional precipitation with ammonium sulfate, ion-exchange chromatography on DEAE-cellulose, gel filtration on Sephadex or Sephacryl and isoelectric focusing or electrophoresis on polyacrylamide gels. In addition, indistinguishable heat inactivation patterns were demonstrated for the two NAT activities utilizing highly purified NAT preparations at two different temperatures. Each of these findings support the coexistence of monomorphic and polymorphic NAT activities on a common protein.

Effect of 2-phenylaminoadenosine (CV-1808) on ischemic ST-segment elevation in anesthetized dogs

The effect of 2-phenylaminoadenosine (CV-1808) against myocardial ischemia was studied in anesthetized dogs. During intravenous infusion of CV-1808 (0.25 and 0.5 microgram/kg/min for 10 min) the ST-segment elevation in the epicardial ECG induced by a 5-min occlusion of a coronary arterial branch was occasionally enhanced in association with cardiac acceleration. In a dose of 0.5 microgram/kg/min, the agent inhibited the ST elevation 30 and 60 min after administration. The same dose did not change myocardial blood flow in the ischemic area despite significant systemic hypotension. In hearts with continuous coronary occlusion, CV-1808 (0.3 and 1.0 microgram/kg, i.v. bolus) increased the retrograde blood flow from the ischemic area immediately after administration, suggesting a collateral vasodilating action. Nifedipine (0.5 and 2.5 microgram/kg/min, i.v. for 10 min) and nitroglycerin (0.5 and 5.0 microgram/kg/min, i.v. for 10 min) had no influence on the ischemic ST-segment elevation, while a significant inhibition was seen with propranolol (0.5 mg/kg, i.v.). A moderate hypotension was induced by CV-1808, nifedipine, and nitroglycerin, while a significant reduction in cardiac function was seen after dosing with propranolol.

[Hematochemical characteristics of miniature pig Göttingen (miniature pig G) (author's transl)]

The biochemical components, enzymes, and other items from the sera and plasma of normal male and female Göttingen miniature pigs from 3 to 20 months of age were investigated. The data were compared with the normal biochemical values of rhesus monkeys, beagle dogs, and JCL: SD rats. The following characteristics were noted. 1. Activities of serum enzymes were higher and their normal ranges wider than in the other experimental animal sera. 2. Of lipid components measured, total cholesterol and phospholipid showed strikingly lower values than in the monkey and the dog. 3. The serum urea nitrogen levels were lower than in the other experimental animal sera. 4. Serum creatinine and potassium were present at relatively high levels, with wide normal ranges. 5. There was a tendency with advancing age toward lower alkaline phosphatase and higher total protein and creatinine. 6. Leucine aminopeptidase was higher while total cholesterol and phospholipid were lower, in the male than in the female. 7. The electrophoretic patterns of serum protein and lipoprotein differed markedly among the species.

Distribution study of a synthetic ACTH analogue in rat tissue

Tissue distribution of (Aib1, Lys17, 18, 19)-corticotrophin-(1-19)-nonadecapeptide amide (690024-S), iv injected to hypophysectomized rats, were surveyed by bioassay. Among the tissues examined. the largest amount of 690024-S was found in the liver during 3 h of search for the injection, while a higher concentration of the peptide per tissue weight was found in kidney. Though a small amount of 690024-S was detected in spleen, heart and lung at an early stage, it was not detectable in other tissues such as brain, stomach, small intestine, thigh muscle, fat or foetus. The peptide was found to be excreted into bile for the duration of about 2 h. It was also found that the elimination of 690024-S in blood followed biphasic first order kinetics.

Sulfoconjugation and glucuronidation of salicylamide in isolated rat hepatocytes

Sulfoconjugation and glucuronidation of salicylamide by isolated hepatocytes were examined with various concentrations of salicylamide and sodium sulfate. The ratio of sulfate to glucuronide formed changed markedly, depending on the concentrations of salicylamide and inorganic sulfate in the medium. The apparent Km value of sulfoconjugation for salicylamide was 0.006 mM, while its Vmax value varied depending on the concentration of inorganic sulfate (e.g., 2.1 and 0.5 nmoles/min/10(6) cells at 1.2 and 0.5 mM inorganic sulfate, respectively). The Km and Vmax values of glucuronidation for salicylamide were 0.19 mM and 1.28 nmoles/min/10(6) cells, respectively, in the absence of sodium sulfate. Glucuronidation was suppressed in the presence of inorganic sulfate. The suppression could be attributable to the competitive consumption of salicylamide by sulfotransferase. Additional in vivo experiments revealed that an extra amount of salicylamide markedly lowered the blood inorganic sulfate levels of rats. The significance of the finding is discussed in conjunction with the variation of the Vmax value of sulfoconjugation with the inorganic sulfate concentration.

Metabolism of isoniazid and free hydrazine formation in isolated rat hepatocytes

Isoniazid (INH) was incubated with isolated rat hepatocytes, and the amounts of acetyl-INH, monoacetylhydrazine, diacetylhydrazine and hydrazine formed were determined by gas chromatography-mass spectrometry (GC-MS). Subsequent analyses of kinetic parameters of metabolic pathways and enzymological study of rat liver homogenate revealed that hydrazine was formed preferentially from INH, catalyzed by soluble hydrolytic enzymes.

An enzyme marker to ensure reliable determinations of human isoniazid acetylator phenotype in vitro

Human liver N-acetyltransferase (NAT) activity undergoes rapid inactivation after death. Thus, in vitro determination of acetylator phenotype in liver autopsies may be unreliable. In the present investigation, the relative stabilities of monomorphic and polymorphic NAT activity were compared in situ in human and rabbit liver of rapid and slow acetylator phenotype. In both phenotypes, the monomorphic NAT activity was considerably less stable than the polymorphic, enabling it to be utilized as an enzyme marker to assure reliable in vitro phenotype classification.

Effects of external cations on calcium efflux from single cells of the guinea-pig taenia coli and porcine coronary artery

1. Single smooth muscle cells were prepared from the guinea-pig taenia coli and the porcine coronary artery by treatment with collagenase, in order to measure the 45Ca flux with special reference to the effects of external cations. 2. In excess [K]o solution, cell suspensions prepared from both tissues showed an increased 45Ca uptake within 3-5 min. In Na-free solution, the cells prepared from taenia coli, but not from coronary artery showed an increased 45Ca uptake. The Ca uptake of the cells paralleled with the tension increase recorded from tissues of both species. 3. The efflux of 45Ca into Ca-free EGTA containing solution was markedly increased by [Na]o in cells from the taenia coli, but not in cells from the coronary artery. 4. The [Na]o-activated 45Ca efflux from cells of the taenia coli was slightly larger in Ca-free solution than in the Ca-containing (10)-4) M) solution. Depolarization of membranes produced by excess [K]o did not effect the [Na]o-activated 45Ca efflux. 5. Increase in [Na]i by treatment with K-free solution suppressed the [Na]o-activated 45Ca efflux in the taenia coli. Re-addition of [K]o reactivated the [Na]o-activated 45Ca efflux. This re-activation was blocked by ouabain. 6. The efflux of 45Ca was slightly activated by [Ca]o in cells from the taenia coli. This [ca]o-activated 45Ca efflux was larger in Na-free solution than in Na-containing solution, thus suggesting interactions between [Na]o and [Ca]o on the Ca efflux. 7. In cells from the taenia coli, 45Ca efflux could still be observed in nominally Na-and Ca-free solution. This residual 45Ca efflux made a large contribution to the total 45Ca efflux. 8. When 45Ca uptake was measured in Na-free (Tris) solution, the [Na]o-activated, [Ca]o-activated and residual 45Ca effluxes of cells from the taenia coli were accelerated, non-selectively. 9. These results obtained with cells prepared from the guinea-pig taenia coli are comparable to the Ca2+ efflux mechanism seen in the squid axon. However, maintenance of low concentrations of [Ca]i seems to require not only the above three 45Ca efflux mechanisms, but also Ca sequestering mechanisms in the cell.