Biomedical subjects
Publications and source records attributed to H Kitagawa.
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Male rats more than seven weeks old showed significantly higher activity of hepatic cytosolic glutathione S-transferase (GST) than females. This sex-related difference in GST activities might be explained by the difference in subunit composition of the enzymes between males and females. The relative proportion of subunit composition of GST between adult male and female rats was as follows: Ya, female greater than male; Yb(Yb'), male much greater than female; Yc, female greater than male. Since phenobarbital (60 mg/kg, i.p. for seven days) induced the Yb subunit as well as Ya subunit, the enzyme activity was more increased in males than in females and the sex difference became more marked. 3-Methylcholanthrene (20 mg/kg, i.p. three times) caused an increase of Ya subunit alone, and then the increased extent was greater in females than in males, and resulted in the disappearance of sex difference.
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14C-N-Ethylmaleimide-S-cysteinylglycine was used to investigate the role of dehydropeptidase-I in the metabolism of glutathione conjugates. The dipeptide was rapidly hydrolyzed to 14C-N-ethylmaleimide-S-cysteine in isolated rat renal cells, and subsequently acetylated to 14C-N-ethylmaleimide-S-N-acetylcysteine. Cilastatin, a specific inhibitor of dehydropeptidase-I, strongly inhibited the hydrolysis of the dipeptide by the isolated cells. In rat kidney homogenates, the marked inhibitory effect of cilastatin was also observed on the hydrolysis of cystinyl-bis-glycine and leukotriene D4, which are dipeptide intermediates in the biotransformation of oxidized glutathione and endogenous glutathione conjugate, respectively. In contrast, the inhibitory effect of bestatin, a potent inhibitor of aminopeptidase-M, was much smaller than that of cilastatin on the hydrolysis of these dipeptides by the renal cells and homogenates. These results suggest that dehydropeptidase-I plays a more important role in the metabolism of glutathione and its conjugates than aminopeptidase-M does.
The effects of oral administration of ketoprofen, indomethacin, (0.1, 1.0 and 3.0 mg/kg), naproxen, flurbiprofen, (0.1 and 1.0 mg/kg), and acetylsalicylic acid (10 and 100 mg/kg) on release of prostaglandin F2 alpha (PGF2 alpha) from isolated pregnant Sprague-Dawley rat uterus and on plasma PGF2 alpha' 17 beta-estradiol and progesterone levels were studied comparatively. The plasma PGF2 alpha level and the rate of release of PGF2 alpha from isolated rat uterus increased progressively from day 18 to 20 of gestation. Ketoprofen, indomethacin, flurbiprofen, naproxen and acetylsalicylic acid reduced the release of PGF2 alpha from the isolated rat uterus and the rise in plasma PGF2 alpha level, and the effects seem to be dose-dependent. A comparative study with intramuscular ketoprofen (0.1 and 1.0 mg/kg) was also carried out. The inhibitory effect of ketoprofen on uterine PGF2 alpha release with intramuscular route was 15.9 times more profound than that with oral route. The anti-inflammatory drugs tested except acetylsalicylic acid were also found to hinder the drop of plasma progesterone level in the late stage of pregnancy but not affect the plasma 17 beta-estradiol level. These results suggest that reduction of PGF2 alpha release from the uterus induced by treatment with these nonsteroidal anti-inflammatory drugs might result in the delay of spontaneous delivery.
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The immunopotentiating activity of heptaminol AMP amidate (HAA), a new derivative of 5'-AMP, was examined in experimental animals. Anti-SRBC PFC activity and antibody titer values augmented for both of single and 4 days consecutive administrations in ICR male mice. The dose of 10 mg/kg was found to cause the maximum enhancement. In spontaneously hypertensive rats, with a state of immunosuppression, 10 days consecutive administrations of HAA at the dose of 10 mg/kg was found to increase significantly the anti-SRBC PFC and antibody titer values. From these results, it is tempting to suggest that HAA may possess an immunopotentiating activity.
The activity of dehydropeptidase I in rat tissues decreases in the order of lung greater than kidney greater than liver-spleen greater than other tissues, while aminopeptidase activity is high in the kidney, and lower in the lung than in other tissues. Dehydropeptidase I was solubilized from the membrane fraction of rat lung by treatment with papain and purified by DEAE-cellulose column chromatography, affinity chromatography on concanavalin-A-Sepharose and high-performance liquid chromatography gel filtration. The purified preparation was found to be homogeneous on sodium dodecyl sulfate/polyacrylamide gel electrophoresis. The relative molecular mass was estimated to be 150,000 by gel filtration, comprising a homodimer of two 80,000-Mr subunits. The enzyme activity was inhibited by cilastatin, o-phenanthroline and ATP. This enzyme catalyzed the hydrolysis of S(substituent)-L-cysteinyl-glycine adducts such as L-cystinyl-bis(glycine) and N-ethylmaleimide-S-L-cysteinyl-glycine, as well as the conversion of leukotriene D4 to E4. Furthermore it catalyzed a hydrolytic splitting of L-Leu-L-Leu, but not S-benzyl-L-cysteine p-nitroanilide, which is a good substrate for aminopeptidase. Our enzyme preparation was immunologically identical to the rat renal dehydropeptidase I. The physiological significance of the pulmonary dehydropeptidase I on the metabolism of glutathione and its adducts is discussed.
B16 mouse melanoma cell lines (B16F1, B16F10 and B16BL6) were able to induce platelet aggregation, and concomitant release of ATP in heparinized platelet-rich plasma (PRP). In citrated PRP, these tumor cells did not induce platelet aggregation. Addition of heparin to citrated PRP enabled these tumor cells to induce aggregation. In heparinized PRP, platelet aggregates induced by B16F10 cells were dissociated by the addition of either 4 mM EDTA, 10 mM CaCl2 or 0.1 micrograms/ml protamine sulfate. B16F10-induced aggregation in heparinized PRP was inhibited by preincubation with anti-fibronectin antibody, but not with antifibrinogen or anti-von Willebrand factor antibodies. B16F10 cells induced aggregation in washed platelet suspension with the addition of heparinized platelet-poor plasma (PPP). Cryoprecipitate from human plasma showed the same effect in the presence of heparin if substituted for PPP. The mixture of purified fibronectin, von Willebrand factor, fibrinogen and heparin were less effective than cryoprecipitate on B16F10-induced aggregation of washed platelets. The results suggest that an interaction between fibronectin and heparin may be important in tumor cell-induced aggregation.