We established here the experimental asthma model in unanesthetized rat, based on the observation of breathing. The effect of disodium cromoglycate (DSCG) was compared between the passive cutaneous anaphylaxis (PCA) model in rat and our experimental asthma model. The systemic anaphylaxis was elicited, in the rat passively sensitized with reaginic antibodies (reagin) against DNP-As in response to challenge with antigen. The longer duration of expiration than that of inspiration was observed in the thoracic breathing of antigen-treated rats. The proportion of animals showing this respiratory distress in thoracic breathing (RDTB) was related to the concentration of antiserum used for the sensitization. The relation between RDTB and the concentration of antiserum was more manifest when the degree of RDTB was considered as a score. Inhibition of DSCG was dose-dependent on RDTB and reagin-induced PCA at more than 1 mg/kg. The maximal inhibition of DSCG (20 mg/kg, i.v.) on RDTB or PCA was observed when it was given 30 s before the challenge with antigen. The effect on RDTB decreased gradually with time after dose, and lasted beyond 60 min similar to the inhibitory activity of DSCG on antigen-induced asthmatic reaction in patients. Whereas, the effect on PCA decreased rapidly, and disappeared within 30 min after dose. These results indicate that RDTB is a principal indicator of respiratory distress induced by reagin, and that the effect of DSCG in asthmatics may be explained by its inhibitory activity on RDTB rather than that on PCA.

View full abstract

The effect of repeated treatment with indomethacin (IND) on the disposition and intestinal absorption of the drug and microsomal drug-metabolizing enzyme activities were studied in comparison with coadministration of the drug and magnesium silicate or dicyclomine in male Wistar rats. The plasma decay curve of IND following a rapid i.v. injection (6 mg/kg) was found to be biexponential. The elimination rate constant (β) of β phase was 0.138±0.015 h^-1. The β after the multiple dosing of IND (6 mg/kg/d for 7 d, p.o.) was significantly decreased as compared with that after a single dosing. In the multiple dose group coadministered magnesium silicate (0.6 g/kg), the AUC_0→∞ was 2 times that after the multiple dosing of IND alone. The repeated administration (8 times every 16 h) with IND (4 mg/kg) alone and IND plus the antacid respectively gave the results similar to those in the multiple dosing. In the multiple treated group with IND alone, the durg-metabolizing enzyme activities were significantly decreased (32-43%) as compared with the control, however, the coadministration of magnesium silicate partly protected the decrease. The intestinal absorption rate constant of IND determined by in situ method was decreased after the multiple dosing of IND alone, but the constant was recovered to the control value after coadministration of the antacid. Following the multiple dosing of IND alone, the centrilobular necrosis in liver and a partial omission of the villi of intestinal epithelium were observed, but the concurrent dosing of magnesium silicate did not produce histopathological changes.

View full abstract

Effects of clofibric acid, probucol, niceritrol, di-(2-ethylhexyl) phthalate (DEHP) and dibutrylphthalate (DBP) on the binding capacities of fatty acid binding protein (FABP) and ligandin fractions in rat liver were investigated. The binding capacity of FABP fraction in male rat liver to oleic acid was increased remarkably on clofibric acid-feeding for 7 d. The administration of either probucol or niceritrol had little influence on the binding capacity of FABP. Both DEHP and DBP increased the binding capacity of FABP in liver of male rats, but the extent of the increase was somewhat less significant in DEHP- or DBP -fed rats compared to that in clofibric acid-fed rats. Sex-related difference in the increase in the binding capacity of FABP fraction to oleic acid by either clofibric acid or DEHP was observed and the extent of the increase in female rats feeding clofibric acid or DEHP was about half of male rats. Effects of any drugs and agents tested here on the binding capacity of ligandin in liver to bromosulfophthalein (BSP) were little if any. The increase in the binding capacity of FABP fraction, but not ligandin in liver was confirmed in vivo by intravenous administration of BSP to rats which had been fed DEHP. In spite of marked increase in the binding capacity of FABP fraction in liver from clofibric acid-fed rats, no remarkable increase in the incorporation of radioactive oleic acid into esterified lipids was observed in vivo.

View full abstract

In order to ascertain the significane of the hydrophobic region in the carrier protein responsible for the D-leucine transport reported previously, the effects of p-chloromercuribenzene sulfonate (PCMBS) were investigated on the transport of D- and L-leucines in Ehrlich ascites tumor cells. The uptake of D-leucine in the presence of PCMBS was inhibited more strongly than that of L-leucine. K_m values for D-leucine uptake increased with increasing concentration of PCMBS, while those for L-leucine showed only a little increase. D-Leucine uptake was restored considerably from the PCMBS inhibition by washing with buffer, whereas L-leucine uptake was only slightly affected. The inhibition of D-leucine exit by PCMBS was also higher than that of L-leucine. These results suggest that the binding site of PCMBS for the carrier protein of Ehrlich cells is involved in its hydrophobic region that would be more significant for the binding of alkyl side chain of D-leucine than that of L-leucine.

View full abstract

Effects of dibenamine on cocaine-induced supersensitivity of isolated vas deferens of guinea pig were examined. Dibenamine at 1.0×10^-7-1.0×10^-5 M attenuated the degree of cocaine-induced increase in sensitivity to acetylcholine without any effect on acetylcholine-contraction. The degree of dibenamine-induced inhibition was dependent on the concentration of dibenamine and inversely related to the concentration of cocaine. Dibenamine at the concentration capable of inhibiting the contractile response to norepinephrine did not affect the degree of the increase in sensitivity to norepinephrine induced by cocaine. Dibenamine diminished the degree of cocaine-induced increase in sensitivity to potassium in standard Tyrode solution and that in maximum response to calcium in partially depolarized vas deferens. Dibenamine at the concentration of 3.2×10^-7 M did not affect acetylcholine-contractions and attenuated potassium-contractions of the preparations exposed 5 min to calcium-free Tyrode solution, but the degree of cocaine-induced potentiation of contractile response in calcium-free Tyrode solution was not affected by dibenamine. These results suggest that cocaine-induced increase in calcium influx from extracellular fluid is selectively inhibited by dibenamine.

View full abstract

Effects of cocaine on the isotonic contractions of isolated vas deferens of intact and reserpinized guinea pigs to acetylcholine were examined. Both cocaine-induced increase in sensitivity to acetylcholine and cocain-induced increase in maximum response of Ca²⁺-contraction was attenuated remarkably by reserpine. However, cocaine-induced increase in acetylcholine- and K⁺- contractions in Ca²⁺-free Tyrode solution were not prevented by reserpine. Acetylcholine-contraction, but not K⁺-contraction, in the preparation exposed for 5 min to Ca²⁺-free Tyrode solution were inhibited by reserpine. Cocaine did not inhibit the cholinesterase activity of vas deferens of guinea pig. These results suggested that presynaptic mechanisms of cocaine-induced supersensitivity are excluded and that inhibitory effect of reserpine on cocaine-induced supersensitivity might be due to the inhibition of cocaine-induced increase in calcium-influx into smooth muscle cells of vas deferens.

View full abstract

1, 3, 3, 5, 5-Pentaziridino-1-thia-2, 4, 6-traiza-3, 5-diphosphorine-1-oxide (SOAz), a new antitumor agent, was evaluated for antitumor activity against various mouse- and rattumor systems. The optimal treatment regimens of SOAz (i.p.) gave 262% and 134% increase in life span (ILS) in mice P338 leukemia and L1210 leukemia implanted intraperitoneally, respectively, and 239% ILS in rats with Yoshida sarcoma of which 86% survived for 60 d after intraperitoneal tumor implantation. The compound showed a definite activity against Lewis lung carcinoma implanted intravenously. The compound also exhibited 80-100% inhibition of tumor local growth in all of four experimental tumor systems used in the present study. In contrast to cyclophosphamide, SOAz was active against B16 melanoma and Meth A, and demonstrated high activity against a subline of L1210 leukemia resistant to cyclophosphamide.

View full abstract

The correspondence of conjugative metabolism rates in vivo and in vitro was studied in rat using p-nitrophenol (PNP) as a model compound. In PNP-glucuronide conjugation, the hepatic intrinsic clearance calculated from K_m and V_max obtained in the isolated liver cells was approximately three times larger than that calculated by the in vivo blood concentration on the basis of the linear pharmacokinetic concepts, but this difference was not considered essential. On the other hand, in PNP-sulfate conjugation, some inhibition in the isolated liver cells, which was not expected in the in vivo blood concentration, was found at more than 5 μM PNP. Such inhibition mechanism could not be elucidated by the inorganic sulfate concentration in the reaction medium. Accordingly, it was suggested that some unknown reaction mechanism still remained to be studied for the applicability of the conjugation rates in the isolated liver cells, especially sulfation rates, to the pharmacokinetic study in vivo.

View full abstract

The level of colony stimulating factors (CSF) in mouse serum was elevated by a single intrapertoneal injection of PSK, a host-mediated antitumor protein-bound polysaccharide obtained from Basidiomycetes. The assay for CSF activity was performed by employing a semisolid methylcellulose culture method using mouse bone marrow cells, and the activity was estimated by an equation well matched with the dose response curve obtained in the CSF assay. A temporary increase of CSF activity within 10 h after the injection of an antitumor polysaccharide, Krestin (PSK) (250-1000 mg/kg) was followed by a fast decline in the activity, but no significant increases were detected in cases of 62.5 and 125 mg/kg PSK injection. The CSF activity in PSK (500 mg/kg)-treated mouse serum was separated into two active fractions by DEAE ion-exchange chromatography, and both fractions were found to induce colonies comprised of cells with the properties of macrophage in regard to morphology, cytochemistry of non-specific esterase, phagocytic function and expression of Fc receptors on the cell surface. The elevation of the serum CSF level due to administration of socalled host-mediated antitumor agents might be one of the tumor-defense mechanisms in vivo.

View full abstract

The effect of furosemide on the elimination, anticoagulant effect and the in vitro and in vivo protein bindings of warfarin was examined in rats. The pharmacokinetic parameters of warfarin and prothrombin complex activity (PCA) after a single i.v. coadministration with warfarin (1.2 mg/kg) and furosemide (1.67 mg/kg) were not significantly different as compared with those in the group injected warfarin alone; however when coadministered with 5 mg/kg of furosemide, the elimination rate constant was significantly increased and PCA was markedly enhanced beyond 60 h after administration. The concurrent treatment with warfarin and a higher dose (10 mg/kg) of furosemide caused an increase in the anticoagulant effect of warfarin even at earier periods after administration. Both the unbound warfarin concentration in serum at 30 min and the amount of warfarin extracted into liver at 2 h after a single i.v. dosing in the coadministered group were significantly increased as compared with those in the group received warfarin alone. Results from in vitro binding studies using bovine serum albumin and rat plasma showed a typical competitive nature of protein binding of warfarin and furosemide at the same binding sites. These results suggest that the interactions, such as the displacement of warfarin binding at albumin binding sites, between warfarin and furosemide are produced, when a high dose of furosemide was coadministered.

View full abstract

Antitumor activities of harringtonine (HA) and homoharringtonine (HO) both belong to cephalotaxus alkaloids were compared with those of vinca alkaloids, vincristine (VCR) and vinblastine (VLB). HA and HO had significant activities against P388 leukemia, L1210 leukemia and B16 melanoma by intraperitoneal injection comparable to VCR and VLB. The therapeutic index (LD₁₀/ED₅₀) of HA and HO in B16 melanoma system was 1.90 and 2.31, while those of VCR and VLB were 1.38 and < 1.00, respectively. The oral administration of these cephalotaxus alkaloids evoked a significant antitumor activity but that of vinca alkaloids induced no activity against P338 and B16 melanoma. The efficacy of HO on various tumor systems was equal or greater than that of HA when comparison was made between these two cephalotaxus alkaloids. In contrast to VCR and VLB, HA and HO demonsrated moderate activity against P388/VCR, a subline of P388 resistant to vincristine. The intraperitoneal injection of VCR or VLB produced an increase in the mitotic index of P388 cells as compared with the control values, but HA or HO decreased it. HA and HO, cephalotaxus alkaloids are a new class of active compounds of plant origin which may differ from the vinca alkaloids in the mechanism of antitumor activity.

View full abstract