The interactions of rat mast cells with a variety of stimuli results in the secretion of a number of mediators through intracellular biochemical events. Calcium and cyclic AMP appear to be two major biochemical factors for the control of cellular activities and are known to activate protein kinases. Another line of evidence indicates that extracellular stimuli induce phospholipid turnover in their target cells. In this article, the author reviews protein phosphorylation and phospholipid metabolism, especially that of inositol phospholipid, during mediator release from stimulated rat mast cells.

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The uptake and the release of [³H] epinephrine ([³H]E) and the release of endogenous E in slices of guinea pig hypothalamus were investigated. [³H]E rapidly accumulated in the slices incubated in Krebs-Ringer solution containing [³H]E. Kinetic analysis indicated two components of E accumulation, one representing a high (K_m1, 7.7×10^-8M and V_max1, 0.13 pmoles/mg/10min) and the other a low (K_m2, 1.8×10^-6M and V_max2, 1.4 pmoles/mg/10min) affinity uptake system. Endogenous E released in response to electrical stimulation was estimated using gas chromatography and mass spectrometry. The electrical stimulation produced a release of both [³H]norepinephrine ([³H]NE) and [³H]E from hypothalamic slices preloaded with [³H]NE. With electrical stimulation of the slices, there was an efflux of [³H]E from tissues preloaded with [³H]E, in a current and frequency-dependent manner. Electrically stimulated release of [³H]E from the slices was inhibited by tetrodotoxin (10^-6M) and by a calcium-free medium containing EGTA (10^-4M), in cases of up to 1 mA of intensity of electrical stimulation. The release of [³H]E induced by electrical stimulation was enhanced by yohimbine, and this effect was suppressed by clonidine. These results provide strong evidence for the neurotransmitter role of this catecholamine in the hypothalamus and suggest the possible existence of a presynaptic regulatory mechaism of E release, through the presynaptic α₂ receptors on the E nerve terminals.

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The number of spleen-rosette forming cells (RFC) and thymus-RFC was assayed on day 4 after immunization with 5×10⁸ sheep red blood cells (SRBC) in BALB/c mice. The number was decreased significantly by oral administration of cyclophosphamide (20 mg/kg) on days −1 and 0. The decrease in spleen-RFC and thymus-RFC by the pretreatment with cyclophosphamide was significantly restored or had a tendency to be restored by traxanox at doses of 3 and 30 mg/kg (p.o.). In addition, traxanox (30 mg/kg, p.o.) protected the reduced number of RFC in mice treated with cyclophosphamide (3 mg/kg, p.o.). Traxanox (30 mg/kg, p.o.) restored the decreased number of spleen-RFC and thymus-RFC in mice pretreated with dexamethasone (0.1 mg/kg, p.o.), and protected the decrease in the RFC in mice treated with prednisolone (10 mg/kg, p.o.). Also, phagocytosis of SRBC by the spleen adherent cells obtained from mice treated with dexamethasone (0.1 mg/kg, p.o.) was inhibited markedly in comparison with that by the spleen adherent cells of untreated mice. The transfer of the spleen adherent cells treated with dexamethasone into syngeneic recipient mice had no effect on the number of spleen hemolytic plaque forming cells (HPFC). On the other hand, the inhibition of phagocytosis of SRBC by spleen adherent cells of mice pretreated with dexamethasone was restored by the addition of traxanox (10 and 30 μM). The transfer of the spleen adherent cells treated with traxanox resulted in an increase in HPFC number. Traxanox (30 mg/kg, p.o.) protected the decrease in spleen-RFC and thymus-RFC in mice treated with indomethacin (1 mg/kg, p.o.) or acetylsalicylic acid (300 mg/kg, p.o.). Traxanox (3 ?? 30 mg/kg, p.o.) restored the decreased number of HPFC, spleen-RFC and thymus-RFC in mice pretreated with carrageenan (0.03 mg). The suppression of phagocytosis of SRBC by spleen adherent cells was restored by the treatment with traxanox (3 and 30 μM). The transfer of the spleen adherent cells treated with traxanox also resulted in an increase in HPFC count. These results strongly suggest that traxanox restores the artificially suppressed immune responses via macrophages.

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Influences of the new compound MY-5116: isoamyl 5, 6-dihydro-7, 8-dimethyl-4, 5-dioxo-4H-pyrano (3, 2-C) quinoline-2-carboxylate and its metabolites were investigated on 48-hr rat homologous PCA (PCA) and the release of histamine from rat peritoneal mast cells induced by antigen antibody reaction (histamine release). MY-5116 (30 mg/kg) inhibited PCA significantly from 10 min to 2 hr after oral administration, and its ID50 (30 min) was 19.1 mg/kg. The inhibitory effect of its main metabolite, MY-1250, was the most potent among all the metabolites, 7HPQ, 8HPQ, 7CPQ and 8CPQ on the PCA (i.v.). Effect of MY-5116 suspended in 1 % CMC on the PCA increased gradually after intravenous administration, but MY-1250 suppressed PCA immediately after intravenous injection. MY-5116 dissolved in DMSO in the concentration of 10^-7 ?? 10^-6 g/ml didn't inhibit the histamine release, but the metabolite MY-1250 inhibited the histamine release. On the other experiment, MY-1250 inhibited the histamine release (IC50: 1.4×10^-7 g/ml), and MY-1250 was 17 times more potent than DSCG (2.4×10^-6 g/ml). From these results, it is suggested that MY-1250 is the main active metabolite of MY-5116.

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The relationship between concentrations of anticonvulsive drugs in the brain and various parameters of maximal electroshock seizures was investigated in mice. Maximal electroshock seizures were elicited with a current intensity (60 Hz, 50 mA for 0.2 sec) through corneal electrodes. Convulsive movements were detected by an accelerometer, amplified and recorded by a polygraph. Concentrations of anticonvulsive drugs in the whole brain were determined by the method of enzyme immunoassay. With various doses of phenobarbital (PB: 5 ?? 35 mg/kg, i.p.), duration of tonic flexion (TF) was prolonged, whereas duration of tonic extension (TE) and clonic convulsion (CL) was shortened in a dose-dependent manner. The correlation coefficient between the PB concentration and the duration of TF, TE or CL was 0.680, −0.882 or 0.409, respectively. The correlation coefficient between the PB concentration and the intensity of TE or CL, measured by the integrated curve of the accelerometer, was −0.847 or 0.440. The correlation coefficient between the PB concentration and the ratio of TE-duration/TF-duration (TE/TF ratio) was −0.901. After administration of phenytoin (PNT), carbamazepine (CBZ) or valproic acid (VPA), a highly negative correlation between the drug level in the brain and the TE/TF ratio was also obtained. In the case of diazepam, clonazepam, ethosuximide or trimethadione, the TE/TF ratio was decreased dose-dependently, but the slope of the dose-response regression line was less steep than that obtained by the administration of PB, PNT, CBZ, VPA or primidone. These results suggest that the TE/TF ratio may be the most reliable parameter for drug evaluation of the anticonvulsive efficacy against tonic-clonic seizures in human patients.

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Single and combination chemotherapies of VP 16-213, a new antitumor agent, were evaluated for its antitumor effect against several murine tumors. Dose-dependent antitumor effects were observed when VP 16-213 was administered via any of the three routes, i.p., i.v. and orally, on days 1 and 5 after i.p. or s.c. inoculation of Ehrlich carcinoma and sarcoma 180. The drug also proved effective against i.v. inoculated EL-LP-12 (subline of Ehrlich carcinoma), i.p. or s.c. inoculated P388 and B16 melanoma, i.p. inoculated colon 26, and s.c. inoculated colon 38 and Lewis lung carcinoma. However, oral administration of the drug was not effective against B16 melanoma, colon 26 and Lewis lung carcinoma despite the fact that the doses employed for this route was higher than those employed for i.v. and i.p. routes. The optimum dosing schedule was also investigated with oral administration of the drug against s.c. inoculated Ehrlich carcinoma. A single dose (day 1) or two doses (days 1 and 5) were more effective than three doses (days 1, 3 and 5) or five consecutive daily doses. VP 16-213 showed additive and more than additive effects in combination with the antitumor agents, cyclophosphamide, BCNU, mitomycin C or cisplatin aganist s.c. inoculated Ehrlich carcinoma and i.v. inoculated EL-LP-12.

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Physiological role of the adrenal medulla was evaluated in the rat with special reference to the age. The adrenal medulla of Wistar-Imamichi male and female rats was enucleated (AdMx) or sham-operated at 3 or 12 weeks of age. Blood pressure was determined by the tailcuff method. 1) Systolic blood pressure in immature and adult-AdMx rats increased progressively 5 ?? 6 weeks after the operation. Plasma renin activities in the AdMx male and female rats tended to be lower than those in controls. 2) There was no significant difference in the pressor response to 50 μg/kg l-adrenaline (s.c.) between control and AdMx groups. 3) Isoproterenol induced a greater decrease in blood pressure in immature AdMx rats. 4) Administration of 200 μg/kg tyramine resulted in a marked increase in blood pressure in the immature AdMx males and in a less marked response in adult AdMx and sham-operated rats. 5) In 24 hr-reserpinized immature AdMx male rats, blood pressure was maintained at approximately 110 mmHg, and tyramine induced a slight increase in the blood pressure. In immaure control male rats, blood pressure showed a decrease to 80 mmHg 24 hr after reserpinization, and no response to tyramine was evident. The results indicated that the lack of an adrenal medulla from the prepuberal age, particularly in male rats, develops alterations in the regulatory system of peripheral noradrenaline release.

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The general pharmacological studies of VP 16-213, an antitumor agent, in the peripheral system were carried out by oral and i.v. administration with laboratory animals. VP 16-213 had no effect on the resting tone and spontaneous motility of all the isolated smooth muscle organs tested at concentrations of up to 10^-5 g/ml. VP 16-213 showed no significant influences on the neuromuscular transmission in the sciatic nerve-tibial muscle preparation of rabbits, on renal function in dogs and rats, on blood sugar level in rabbits, and on charcoal meal transport in mice. At a dose of 20 mg/kg, i.v., VP 16-213 reduced gastric secretion in rats. Antiinflammatory, local irritation and hemolytic effects were not observed after the administration of the drug. Single administration of VP 16-213 had orally no effect on the excretion of serum BSP in rats. However, successive administration of the drug (20 mg/kg/day) once daily for 10 days significantly depressed it. VP 16-213 decreased the number of hemolytic plaque forming cells in the spleens of immunized mice.

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The effect of THS-201, a new intra-articular steroid, on inflammations was examined using acute, subacute and chronic experimental models, and the antiinflammatory action of THS-201 was compared with those of reference steroids such as triamcinolone acetonide (TA), methylprednisolone acetate (MPA), hydrocortisone acetate (HA) and halopredone (HP). Reference steroids, which were given s.c. or locally, dose-dependently inhibited carrageenin-induced foot-pad edema, sodium carboxymethyl cellulose-induced leukocyte migration, cotton pellet granuloma and carrageenin granuloma pouch in rats. Although the inhibitory effects of reference steroids on such inflammations were unrelated to their administration routes, the inhibitory potency decreased in the following order: TA>MPA>HA=HP. THS-201 even at a dose of 100 mg/kg had no inhibitory effects on such inflammations when given s.c. By contrast, THS-201 given locally had anti-inflammatory actions: the inhibitory potency of THS-201 in chronic models was higher than that of TA, but was lower in the acute models than that of HA. In antigen-induced arthritis in rabbits, the inhibition of swelling of inflamed joints by intra-articular injection of THS-201 (2 mg/joint) persisted more than 30 days, suggesting that the elimination of THS-201 from the injected site was very slow. In contrast to the finding of reference steroids, THS-201 showed no systemic adverse reactions in all experiments. The results, which are in agreement with the findings of labeled THS-201 into arthritic joints, indicate that THS-201 can strongly inhibit recurrence of inflammation as compared with reference steroids tested. Thus, THS-201 may be useful for the treatment of rheumatoid arthritis when it is applied intra-articularly.

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