The experiments were conducted in order to examine the mechanism of hyperthermia induced by l-ephedrine in rats. β-Adrenoceptor agonists have been known to enhance normal body temperature. Therefore, the effect of various β-adrenoceptor agonists on body temperature in rats was examined to clarify the mechanism of action of l-ephedrine. The results showed that drugs with β₂-adrenoceptor agonist activity and l-ephedrine caused hyperthermia in rats and this effect was selectively inhibited by pretreatment of animals with propranolol (a mixed β-adrenoceptor antagonist) or butoxamine (a selective β₂-adrenoceptor antagonist). These results suggest that hyperthermic action of l-ephedrine may largely be due to its effect on β₂-adrenoceptors.

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Camazepam (CZ), a benzodiazepine, was biotransformed to more than ten metabolites. After intravenous and oral administration of these metabolites to rats, CZ, tempazepam (TZ), oxazepam (OZ), and hydroxy CZ (M₅) were found to possess pharmacological activities. The brain-to-plasma concentration ratios of CZ and these active metabolites were essentially constant with time after oral administration of CZ. Thus the brain, target organ, was kinetically included in the plasma compartment. The extent of binding of these compounds to plasma protein was independent of concentration tested. Plasma levels of an unchanged drug and its active metabolite (s), and muscle relaxation effect (the impairment of rota rod performance) were measured at 0.5 to 8 h after oral administration of 2 to 3 doses of CZ, TZ, and OZ to rats. When the effect and plasma level data were computer-fitted to a simple Hill equation or a modified Hill equation including competitive factors, the modified Hill equation was found to be adequately applicable to the concentration-effect relation. The parameter values thus obtained could predict the contribution of the administered drug and its active metabolite (s) to the observed pharmacological effect after administration.

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Kinin level in the rat brain was determined using a highly sensitive radioimmunoassay with a purified tracer. Monoiodinated Tyr⁸-bradykinin (BK) was separated from the non-iodinated peptide by paper chromatography, using 0.2M ammonium acetate as the developer. This purification method resulted in a ligand with a highly specific radioactivity (2200 μCi/nmol), which raised the radioimmunoassay sensitivity about 5-fold and enabled to determine the brain kinin level in the rat. The brain extract competed with iodinated antigen for an antibody binding site in the same manner as did authentic BK, indicating the immunological idintity of them. Brain kinin level was estimated to be 139±79 fmol BK eq/g (n=7) in an adult male rat of the Sprague-Dawley strain.

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p-Nitrophenyl vinyl ether (NPVE) was metabolized to p-nitrophenol and glycolaldehyde via an epoxide by rat hepatic microsomes. The cofactor requirment and effects of monooxygenase inhibitors indicated that the oxidative metabolism of NPVE was mediated by microsomal cytochrome P-450. Epoxide hydrolase plays a minor role, because a strong epoxide hydrolase inhibitor, 3, 3, 3-trichloropropene oxide, showed a weak inhibitory effect on the p-nitrophenol formation. The epoxy intermediate is so labile that the hydrolysis of the epoxide proceeds mostly nonenzymically even at a neutral pH. Induction experiments suggested that NPVE was susceptible to a wide varieties of cytochrome P-450 species. Thus, a convenient and sensitive method for the assay of olefinic epoxidase activity in hepatic microsomes was developed with NPVE as a substrate.

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The transport mechanism of amino-β-lactam antibiotics across in vitro rat ileum was examined using the electrophysiological technique in comparison with that of dipeptides. The changes in the transmural potential difference (PD_t) induced by a series of amino-β-lactam antibiotics were correlated with the absorption percentage of these antibiotics from the in situ rat intestinal loops. On the contrary, β-lactam antibiotics without α-amino group such as dicloxacillin, methicillin and cefazolin did not induce such a stable change of PD_t. The changes in PD_t induced by cyclacillin (ACPC), cefadroxil (CDX) and glycylglycine (Gly-Gly) became saturable when the concentration of the substances increased. The half saturation concentration for ACPC, CDX, and Gly-Gly estimated from the changes in PD_t was nearly identical with that determined from influx of the substrates in the everted intestinal sacs. The mutual inhibition between amino-β-lactam antibiotics and Gly-Gly was observed in their induced PD_tS. The changes in PD_t induced by amino-β-lactam antibiotics were independent of those of glucose, glycine, and cefazolin. By the removal of Na⁺ from the mucosal solution, the PD_t decreased one-fifth of the PD_t induced in the presence of Na⁺. These results suggest that amino-β-lactam antibiotic-induced PD_t relates to the Na⁺ ion fluxes as reported for dipeptides.

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Oral acute toxicity of medium chain glyceride (MCG) was studied in mice and rats. In mice and rats, clinical signs such as irregular respiration, laxity of movement, staggering gait and loss of righting reflex appeared after single oral administration of MCG at a relatively large dose. The LD₅₀ values determined in male and female mice were 26.9 and 28.5 ml/kg, and in male and female rats were 27.4 and 26.7 ml/kg, respectively. In order to evaluate the biological safety of MCG suppository of cefmetazole sodium (CMZ), its local irritation on the mucous membrane was studied. Primary eye irritation of MCG suppository of CMZ was studied in rabbits. Although mild irritation was seen in conjunctivae, no remarkable changes were observed in cornea and iris. Furthermore, primary effect of MCG suppository of CMZ on the rectal mucous membrane was studied macro- and micro-scopically. It was observed that remarkable histological changes of rectal mucous membrane by MCG suppository of CMZ were not observed in all animals used.

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The mechanisms of the promoting effect of medium chain glyceride (MCG) containing glyceryl mono-, di- and tri-caprylate on rectal absorption of water soluble drugs were investigated. It was found that the solubility behavior of the drugs in mucosal fluids on the surface of the membrane are critical factor for the enhanced rectal absorption. Moreover, the drugs to be readily absorbed from MCG base may be ones of low partition coefficients to MCG phase as well as high solubility in water. And it was found that MCG can't be absorbed from the rectum, different from oral administration, suggesting an interaction of MCG with absorption membrane, rather than the carrier effect of MCG itself. Furthermore, from the results in the pretreatment experiments and additional administration of MCG alone, it was suggested that the interactions of MCG with the membrane components, as well as the induction of biological or physiological changes, may be at least partly responsible for the promoting effect of MCG.

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The promoting effects of medium chain glyceride (MCG) on the rectal absorption of β-lactam antibiotics were compared among various experimental animals (such as rats, rabbits and dogs). The plasma levels of cefmetazole (CMZ) after rectal administration, when MCG was used as the vehicle, significantly increased in all animals, but the bioavailability of CMZ was greatly varied among the animal species ; the bioavailability of CMZ in dogs was apparently less than those in other animals (rats=rabbits > dogs). However, in dogs, the promoting effect of MCG on the rectal absorption of CMZ increased by addition of nonionic surfactants such as ether-type (Brij 30^[○!R] and Brij 35^[○!R]) and ester type (Nikkol MYL-10^[○!R]). And the promoting effect of surfactants in the MCG vehicle is not always correlated with blood hemolysis, suggesting contribution of other physicochemical or biological factors.

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The effect of synthetic surfactants and their binary mixture with a physiologic one, sodium taurocholate (STC), on the intestinal absorption of drugs was examined in rats by using the in situ recirculation technique. Synthetic surfactants investigated in this study were nonionic polysorbate 80 (PS-80), cationic cetyltrimethylammonium bromide (CTAB), and anionic sodium lauryl sulfate (SLS). The surfactant action on the mucosal membrane seemed to be the same magnitude as the stronger one of the two components, except in the case of CTAB, as estimated by the enhancement effect on sulfaguanidine absorption. The action of CTAB was increased in the presence of STC. The action of surfactants in the aqueous solution, an intraluminal action, was examined by using quinine as a model drug. The micellar interaction of the drug with an ionic surfactant, CTAB or SLS, was reduced by the addition of STC, whereas, that with a nonionic surfactant, PS-80, was increased as estimated by a dynamic dialysis technique. The inhibitory effect on quinine absorption was approximately proportional to the degree of the micellar complex formation. Two other model drugs, imipramine and sulfadimethoxine, were further examined and the possible mechanisms of these effects were discussed.

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The alterations of various enzymes responsible for drug metabolism and heme metabolism were examined in the liver of female rats treated with Bacillus Calmette-Guerin (BCG) and Corynebacterium parvum (CP). Hepatic drug metabolizing enzyme activities and microsomal cytochrome P-450 and b₅ content were significantly decreased for up to 15 and 10 d by a single i.v. administration of BCG and CP, respectively. In contrast, microsomal heme oxygenase activity was markedly increased after BCG and CP treatment and the increased enzyme activity was sustained in parallel with the decrease of drug metabolizing enzymes. Both BCG and CP also caused a significant decrease of δ-aminolevulinic acid synthetase activity shortly after their administrations. The decreased enzyme activity returned to normal levels by 12 h after the treatment of rats with BCG and CP. In addition, hepatosplenomegaly was observed in BCG and CP treated rats. Dose related changes of these microsomal enzymes were seen following the administration of BCG and CP. Additionally, there were sex differences in the effects of BCG and CP on the alteration of microsomal enzymes, female rats being more sensitive than male rats. These results suggest that the decrease of cytochrome P-450 and b₅ content and drug metabolizing enzyme activities by BCG and CP could be related, at least in part, to the prolonged increase of heme oxygenase activity, that may lead to the increased breakdown of heme available for the synthesis of these hemoproteins.

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Uridine diphosphate (UDP)-glucuronosyltransferase (GT) active on androsterone (AD) and 4-nitrophenol (NP) was solubilized from male rat liver microsomes of the Wistar strain. The precipitate obtained in the 60%-satd. ammonium sulfate was purified by diethylaminoethyl (DEAE)-cellulose chromatography and affinity chromatography on UDP-hexanolamine Sepharose 4B. DEAE-cellulose chromatography showed the existence of two peaks of GT active on AD and NP. Peak I was found in rats with the high-activity and low-activity phenotypes in terms of AD glucuronidation and had high NP-GT and low AD-GT activities. In contrast, peak II was found only in rats with the high-activity phenotype, corresponded to high AD-GT activity and had comparatively low NP-GT activities. The corresponding peak in rats with the low-activity phenotype had only NP-GT activity. Comparison of K_m values for AD obtained from microsomes and purified enzymes provides evidence that AD-GT isoenzyme should be deficient in Wistar rats with the low-activity phenotype and that AD glucuronidation should be catalyzed poorly by other GT isoenzyme in these rats.

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FI-302, N-(3-piperidinopropyl)-4-methyl-6-trifluoromethyl-furo [3, 2-b] indole-2-carboxamide, is a new non-steroidal anti-inflammatory compound. The analgesic effect of FI-302 was investigated in comparison with those of non-steroidal anti-inflammatory drugs (NSAIDs). In the tail pressure, hot plate and D'Amour and Smith methods, FI-302 showed a potent analgesic effect, its efficacy being about 2 to 7 times greater than those of aminopyrine, mepirizole and tiaramide. On the other hand, in these methods, aspirin, ibuprofen and phenylbutazone had little or no effect. FI-302 showed a potent inhibitory effect on the vocalization response produced by electrical stimulation. Moreover, the analgesic effect of FI-302 after intracerebroventricular injection was about 58 to 278 times more potent than those of tiaramide and ibuprofen, and about 1/6 that of morphine. However, the analgesic effect of FI-302 was not antagonized by levallorphan. From these results, it appears that FI-302 has potent analgesic effects which may be produced by both peripheral and central mechanisms, but it is a non-narcotic compound. Consequently, FI-302 should be suitably applicable for clinical purposes.

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