[Anti-inflammatory activity of benzo(c) phenanthridine derivatives and possible mechanisms of action (author's transl)]

Of five newly synthesized benzo[c]phenanthridine derivatives tested, the two compounds, BPD-I and BPD-II were found to have potent anti-edematous activity with intraperitoneal administration to S.D. rats. BPD-I showed a marked inhibitory effect against acute inflammation such as induced rat paw edema and leucocyte emigration and protein exudation by means of CMC pouch method and capillary permeability enhancement induced by various phlogists. This compound also inhibited subacute and chronic inflammatory responses such as granuloma formation induced by croton oil or cotton pellet. The anti-inflammatory activities of this compound resembled those of hydrocortisone. The inhibitory effects of carragenan edema and capillary permeability enhancement by ATP were strikingly reduced in adrenalectomized rats suggesting involvement of the hypophysis-adrenal systems. Rat serum corticosterone level and hepatic tyrosine aminotransferase activity (TAT) were then measured after BPD-I injection. The serum corticosterone level was increased and shortly after the elevation of corticosterone, hepatic TAT levels also increased. Thus it is concluded that the corticosterone release from adrenal gland plays a role in the anti-inflammatory action of BPD-I.

Possible regulation of thiamine diphosphatase activity in rat brain microsomes by lipids

The effects of various treatments, which affect membrane structure, on microsomal thiamine diphosphatase and thiamine triphosphatase activities of rat brain, were examined. The treatment of micorosomes at alkaline pH caused a 2-fold activation of the thiamine diphosphatase, this being related to a change in membrane structure which was evidenced by a decrease of the turbidity of the microsomal suspension. Repeated freezing and thawing after hypo-osmotic treatment also increased the activity of microsomal thiamine diphosphatase. In addition, the thiamine diphosphatase activity was enhanced by treatment of the microsomes with phospholipase C or acetone. This lipid depletion resulted in a marked reduction in the apparent Km value of the thiamine diphosphatase with a corresponding loss in heat stability of the enzyme. We found further that brain thiamine diphosphatase was solubilized by Triton X-100. This decreased the phospholipid content in the preparation, but did not affect the apparent Km value and heat stability of the enzyme. In contrast with thiamine diphosphatase, thiamine triphosphatase was inactivated by treatment at alkaline pH or with acetone. However, treatment with phospholipase C did not affect the activity of thiamine triphosphatase.

Tissue distribution and characteristics of xanthine oxidase and allopurinol oxidizing enzyme

Tissue distribution and levels of allopurinol oxidizing enzyme and xanthine oxidase with hypoxanthine as a substrate were compared with supernatant fractions from various tissues of mice and from liver of mice, rats, guinea pigs and rabbits. The allopurinol oxidizing enzyme activities in liver were quite different among the species and the sex difference of the enzyme activity only in mouse liver. In mice, the highest activity of allopurinol oxidizing enzyme was found in the liver with a trace value in lung, but the enzyme activity was not detected in brain, small intestine and kidney, while the highest activity of xanthine oxidase was detected in small intestine, lung, liver and kidney in that sequence. The allopurinol oxidizing enzyme activity in mouse liver supernatant fraction did not change after storage at -20 degrees C or dialysis against 0.1 M Tris-HCl containing 1.15% KCl, but the activity markedly decreased after dialysis against 0.1 M Tris-HCl. On the contrary, the xanthine oxidase was activated 2 to 3 times the usual activity after storage at -20 degrees C or dialysis of the enzyme preparation. These results indicated that allopurinol was hydroxylated to oxipurinol mainly by the enzyme which is not identical to xanthine oxidase in vivo. A possible role of aldehyde oxidase involved in the allopurinol oxidation in liver supernatant fraction was dicussed.

Thiamine diphosphatase in rat small intestine

TDPase is located mostly in the proximal portion of the small intestine and its activity, like that of ALPase, decreased markedly in thiamine deficiency. The decreased enzyme activities were restored after thiamine or vitamin D3. Kinetic and other studies of the purified enzyme indicated the identity of the two enzymes.

Effect of taurine on responses to noradrenaline, acetylcholine and ouabain in isolated auricles from digitalized guinea pigs

Responses of the isolated heart from the guinea pig treated chronically with digitoxin until the T wave had disappeared were studied. The development of the abnormal ECG pattern was abolished by a simultaneous injection of taurine and digitoxin. Taurine also inhibited the change by digitoxin of the responses to acetylcholine and ouabain but not to noradrenaline. The causal relationship between the inhibitory effect of taurine and prevention of the development of arrhythmias remains obscure.

Effects of various drugs on serum free and total tryptophan levels and brain tryptophan metabolism in rats

Various drugs known to bind to serum albumin were examined to determine whether or not they influenced the level of free tryptophan in serum in vitro and in vivo. Possible relationships between the serum free tryptophan level and serotonin (5-HT) synthesis in the brain and the hypothermic effects of these drugs were investigated. Of the drugs examined, sodium salicylate, sodium benzoate and indomethacin caused a significant increase in the concentration of serum free tryptophan and stimulated the synthesis of 5-HT in the brain. Hypothermia induced by salicylate and indomethacin was potentiated by pretreatment with pargyline, a monoamine oxidase inhibitor. Administration of benzoate did not cause any change in body temperature, but after pargyline a hypothermia did occur. However, pretreatment with parachlorophenylalanine, an inhibitor of 5-HT synthesis, did not influence the hypothermia induced by salicylate and indomethacin. Relationship between the hypothermic effect and the increase of 5-HT synthesis in the brain after a large dose of salicylate and indomethacin is discussed.

Effects of reducing and oxidizing agents on the action of bleomycin

The effects of reducing agents, such as 2-mercaptoethanol, dithiothreitol, L-ascorbic acid, or sodium borohydride, and oxidizing agents, such as hydrogen peroxide or dehydroascorbic acid, on the in vitro action of bleomycin were investigated. After the incubation of DNA with a low concentration of bleomycin and a reducing or oxidizing agent, single strand breaks were mainly caused in the DNA molecules. The degradation of DNA was largely prevented by the removal of oxygen, or by the addition of divalent cations or of S-(2-aminoethyl)isothiuronium bromide hydrobromide, a radical scavenger, to the incubation mixture. Preincubation of bleomycin with these reducing or oxidizing agents reduced the DNA-degrading activity of the antibiotic. However, this reduction in activity was observed even in the absence of oxygen, or in preincubation mixture supplemented with radical scavenger.

Effects of extracts of rat tissues on the action of bleomycin

The cell sap (105 000 times g supernatant) of various tissues of rats caused DNA degradation in the presence of bleomycin. The activity was fractionated into two peaks by column chromatography on Sephadex G-25. The activity in Peak A (excluded fraction) appeared to be due to some proteinaceous entity, while that recovered in Peak B (retarded fraction), constituting about 90% of the total activity, seemed to be due to ascorbic acid, judging by results of further gel filtration and the effect of treatment with ascorbate oxidase. Incubation of bleomycin with Peak A or B caused loss of the ability of the antibiotic to degrade DNA. It is proposed that the action of bleomycin on DNA, and its inactivation by tissue extracts, depend, at least in part, on the presence of ascorbic acid.

Effect of various nucleotides and drugs on microsomal thiamine diphosphatase activity in rat brain

The basic properties of microsomal thiamine diphosphatase (TDPase) in rat brain were examined. It was mainly localized in the microsomal fraction. Microsomal TDPase showed an absolute requirement for divalent cation which was best satisfied by Ca++. Theophylline (1 mM), NADP (0.1 mM) and NADPH (0.1 mM) significantly inhibited its activity. However, caffeine, theobromine, NAD and various putative neurotransmitters did not affect the enzyme activity. UDP was inhibitory and IDP was a competitive inhibitor, but ATP had no effect on the enzyme activity.

[Inhibitory effect of taurine on ouabain-induced arrythmia]

Myocardial taurine level was found to be greater in the rat than in the guinea-pig. Taurine inhibited the development of arrhythmias caused by the i.v. infusion of ouabain in the rat. When ouabain induced arrhythmias, the myocardial taurine level decreased. Both effects were blocked by pretreatment of propranolol. The uptake of taurine into the heart did not necessarily result in the reversal of the PR interval prolonged by ouabain. The protecting effect of taurine against ouabain toxicity was not dependent upon the change in myocardial total ATPase activity.