The mechanism of potentiation of 2-sec-butylphenyl N-methylcarbamate (BPMC) toxicity by O, O-dimethyl O-(3-methyl-4-methylthiophenyl) phosphorothioate (fenthion) in mice was investigated in relation to BPMC metabolism in the liver. Simultaneous administration of BPMC and either one of the thiophosphates (fenthion, its sulfoxide and sulfone) in a dose of 1/40 of its LD₅₀ resulted in a 2-to 3-fold potentiation. On the other hand, one hour pretreatment with these thiophosphates in the same dose resulted in a 7- to 9-fold potentiation of BPMC toxicity, but that with fenthion oxon resulted in only a 2-fold potentiation of BPMC toxicity, but that with fenthion oxon resulted in only a 2-fold potentiation. Plasma levels of BPMC were significantly increased by pretreatment with the thiophosphates, but not by the oxon. In an in vitro study, an inhibition of hepatic microsomal metabolism of BPMC and a decrease of cytochrome P-450 content by thiophosphates were observed at the concentration of 10 μM, but not by 25 μM of oxon. In an in vivo study, an inhibition of hepatic microsomal metabolism of BPMC, aminopyrine and aniline by the thiophosphates pretreatment were observed in doses of 1/40 of their LD₅₀'s, but not by the oxon in doses of up to 4/10 of its LD₅₀. Cytochrome P-450 content was decreased by the thiophosphates in doses of 4/10 of their LD₅₀'s, but not by the oxon. These results suggested that the inhibition of BPMC metabolism might be, at least in part, the mechanism for the fenthion-induced potentiation of BPMC toxicity and that desulfuration of fenthion might be responsible for the inhibition of BPMC metabolism.

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The effects of concanavalin A (Con A) on plasma and brain concentration of aspirin (Asp) were investigated in rats. When Asp was administered in rats treated with Con A, the plasma and brain concentration of Asp and its metabolites (salicylic acid (SA), salicyluric acid (SU) and gentisic acid (GA)) were increased. Distribution of Asp and its metabolites into the hippocampus, striatum and hypothalamus were increased by treatment with Con A. Asp esterase activities in the small intestinal mucosa, liver and brain were increased by pretreatment with Con A, but these enzyme activities were decreased by a high dose of Con A. The inhibitory effect of Asp, SA, SU and GA on the writhing induced by acetic acid in Con A-pretreated mice was stronger than that in the control. A lowering of rectal temperature, after the administration of Asp, was stronger in Con A-treated rats than in control rats. These results suggested that Con A facilitated the absorption of Asp and enhanced the transfer of SA into the brain, and increased Asp esterase activities in various tissues.

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One hundred and sixty-eight different specimens of human carcinoma of the lung were tested for in vitro drug sensitivity using the human tumor clonogenic assay (HTCA) originally described by Hamburger and Salmon. One hundred and twenty-two (73%) specimens grew adequately for chemosensitivity testing. Most tumors were resistant to chemotherapeutic drugs, but in vitro sensitivity, regardless of the type of drugs, varied markedly from specimen to specimen. Although response rates to individual drugs ranged between 9% and 23%, half the specimens tested were sensitive in vitro to at least one drug. A higher in vitro sensitivity rate was observed in small cell lung carcinoma (31%) than in non-small cell lung carcinoma (17%). The frequency of in vitro sensitivity was greater for patients who had received no prior chemotherapy than those who were in relapse. These in vitro results are similar to current clinical experience. There was a significant association between in vitro sensitivity of cells from a primary tumor as compared to its metastases. Overall HTCA appears to be useful in selecting appropriate chemotherapy for individual patients with carcinoma of the lung.

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In order to elucidate the dependency of pyrogenicity of lipopolysaccharide (LPS) on the lipid A structure, we investigated the pyrogenicity of both LPS and lipid A prepared from Mima polymorpha var. oxidans which is deficient in 3-hydroxymyristic acids linked to the 3-hydroxy group of other fatty acids. LPS and lipid A were also prepared as reference compounds from Escherichia coli UKT-B. Furthermore, the establishment of reliable indices for pyrogenicity was undertaken. The following results were obtained. 1) The correlation in linearity was demonstrated between maximal increase in body temperature (ΔT_max) and dose of LPS or lipid A complexed with bovine serum albumin (BSA). The dose-response curves based on ΔT_max were more reliable statistically than the Fever Index-4h representing the area under fever curves for 4 h. 2) The minimum pyrogenic dose (MPD) of E. coli LPS was 1.6×10^-3 μg/kg i.v. In contrast, the MPD of M. polymorpha LPS was 7.0×10^-3 μg/kg i.v. By intracisternal injection, the MPD of E. coli LPS was 2.5×10^-6 μg/kg and that of M. polymorpha LPS 1.0×10^-4 μg/kg. 3) The end points of Limulus amoebocyte lysate gelation were 10^-5 μg/ml in E. coli LPS and 10^-3 μg/ml in M. polymorpha LPS. 4) The MPDs of lipid A/BSA complexes by i.v. injection were 0.15 μg/kg in E. coli and 2.5 μg/kg in M. polymorpha. 5) The rabbits immunized with E. coli lipid A/BSA complex acquired pyrogenic tolerance to the parent LPS but the cross tolerance to M. polymorpha LPS was not observed. These results indicated that certain differences in lipid A structure may be dominant factors for LPS-induced fever. However, it was suggested that the polysaccharide regions of a LPS molecule may also play an important role in LPS-induced fever.

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The spleen cells in tumor-bearing and normal mice treated with Krestin (PSK), mitomycin C (MMC) or adriamycin (ADM) were analyzed by cell electrophoresis and flow microcytometry. In normal mice, the splenocyte electrophoretic mobility histogram was observed as a bimodal pattern, and low and high mobility cells (LMC and HMC) corresponded with B and T cells, respectively. In sacroma-180-bearing mice, an intermediate mobility peak (IMC) appeared between the low and high peaks. Although every anticancer drug depressed the IMC when the tumor was cured, MMC reduced the absolute number of splenic Ig⁺ and Thy-1⁺ cells, and ADM injured Ig⁺ cells in normal as well as in tumor-bearing mice. PSK, however, depressed splenomegaly by tumor-burden in spite of a slight increase in splenocytes of normal mice. In a previous paper, it was reported that the thymocyte mobility histogram was restored to a normal pattern by treatment with PSK in tumor-bearers, while it was made more abnormal by treatment with MMC because of injury to cortical thymocytes. From these results, it may be considered that an anticancer drug which restored the splenocyte mobility histogram to a normal pattern without damages to thymocytes is preferable for cancer therapy.

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In order to determine the relationship between structure and distribution in monoquaternary ammonium ions, the distribution of a series of ¹⁴C-labeled tetraalkylammonium and substituted trimethylanilinium ions in mice were comparatively studied by means of whole-body autoradiography and radioassay. The partition coefficient in n-octanol/water were also determined. With tetraalkylammonium, the concentration in blood and tissues decreased in the order of tetramethyl, tetraethyl and tetrapropylammonium, which was opposite to expectation based on their partition coefficient values, but was in the order of increasing steric hindrance at the cationic head. With substituted trimethylanilinium, the concentrations in the blood, skeletal and cardiac muscles, diaphragm and salivary gland after i.v. injection to mice increased in the order : m-NO₂<Cl<OCH₃<H<CH₃. This did not coincide with the order of increasing the partition coefficients, but coincided with the decrease of the Hammett σ-constants of the substituent. These results were interpreted on the basis of the assumption that the ion-pair formation of the cationic head with an anionic site of the tissue macromolecules played an important role in determining distribution. It was pointed out that although the lipophilic character of the molecule has been often cited as the most important factor determining the distribution of the drugs, the ionic character of the molecule or of the functional group can participate as a more important factor in determining tissue distribution.

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The intestinal absorption of tetramethylammonium (TMA) and its derivatives from rat jejunum has been investigated with an in situ loop method and an in vitro everted sac method. At a low concentration, TMA was absorbed rapidly from the in situ intestinal lumen without being metabolized in the tissue and the rate of absorption was dependent upon the concentration used. The profile of TMA absorption included two processes, i.e. saturable and non-saturable. The absorption of TMA was inhibited competitively by analogs that have a Ntrimethyl group in their structure. Among them, choline showed the strongest inhibition to TMA absorption. The inhibitory potency of these analogs was related to their chemical structure. Although TMA was not transported into the intracellular fluid of the everted intestine against a concentration gradient, the tissue accumulation of TMA was inhibited by 2, 4-dinitrophenol (2, 4-DNP), a metabolic inhibitor, and was highly dependent upon the incubation temperature. These findings demonstrate that TMA is absorbed through the rat small intestine by a carrier mediated transport system. An apparent K_t of 0.73 mM and a maximum V of 11.5 nmol/g tissue wet wt/min were determined by an in situ loop method. It was also suggested that the endogenous quaternary ammonium compound, choline, might be absorbed by the same carrier system.

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Forty-three different cardiac steroids having a doubly linked sugar and related compounds were tested for inhibition of Na⁺, K⁺-adenosine triphosphatase from guinea pig heart, and the structure-activity relationship has been discussed. The doubly linked glycosides showed higher activities than the respective genins. The inhibitory activities of these compounds were also dependent upon the presence of ring C substituents. The bufadienolide rhamnosides exhibited greater than three times the inhibitory activity of the parent genin, while the glucosyl residue exerted no significant activity.

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Using a mucolytic agent, N-acetyl-L-cysteine (NAC), the structure of rat gastric mucous glycoprotein (GP) and its participation in prostaglandin cytoprotection were studied. Treatment of the undegraded native mucous GP with 20% NAC resulted in a marked reduction in molecular weight as obtained in the case of treatment with 0.5 M β-mercaptoethanol. The amount of GP remaining in the gastric tissue, including the mucous layer after 3 h-incubation was defined as an indication of the mucous adhesiveness to the gastric mucosal surface. The adhesiveness was markedly decreased by the in vitro or in vivo treatment with NAC. The cytoprotective effect of prostaglandin E₂ was significantly reduced by pretreatment with NAC. Elution profiles of mucous GP on Sepharose CL-2B showed a good correlation between decrease in the amount of the undegraded native mucous GP and the severity of gastric damage. In addition, the collapse of the native mucous GP into its subunits resulted in a decrease in the adhesiveness. These observations suggest that the maintenance of the native mucous GP is an essential factor for prostaglandin cytoprotection.

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The treatment of AH130 cells with isoproterenol (IPN) resulted in an increase in the activity of cyclic adenosine 3' : 5'-monophosphate (cyclic AMP) phosphodiesterase with a low K_m value and a decrease in IPN-stimulated activity of adenylate cyclase. The activity of cyclic AMP phosphodiesterase was increased by IPN in a dose-dependent manner and reached a maximal increase at 30 min after the addition of 10^-4M IPN. The addition of mitomycin C (MMC) at 15 min after the initiation of the treatment with IPN inhibited the increase in the activity of cyclic AMP phosphodiesterase in a dose-dependent manner. The extent of the development of desensitization, which was observed as a decrease in IPN-stimulated activity of adenylate cyclase, was dependent on the treatment time with IPN and the concentration of IPN. Desensitization was also observed as a decrease in prostaglandin E₁-stimulated activity but not in basal and NaF-stimulated activity. The combined treatment with IPN and MMC showed a higher IPN-stimulated activity of adenylate cyclase than with a single treatment with IPN. This effect resulted from the enhancement of IPN-stimulated activity of the enzyme by MMC itself. These results show that the treatment of AH130 cells with IPN caused an induction of cyclic AMP phosphodiesterase and the development of desensitization of adenylate cyclase. Since the combined treatment with MMC inhibited both phenomena, the high intracelullar cyclic AMP level appeared to be maintained by the combined treatment for a longer term than by a single treatment with IPN.

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Isoproterenol (IPN)-stimulated activity of adenylate cyclase was enhanced in a dose-dependent manner by exposure of AH130 cells to mitomycin C (MMC). The enhancement was also observed in prostaglandin E₁-, guanine nucleotide analog-, NaF-, cholera toxin- and forskolin-stimulated activities of the enzyme but not in manganese-stimulated activity. In addition, even when the cells pretreated with islet-activating protein were exposed to MMC, IPN-stimulated activity of adenylate cyclase was enhanced. Anaerobic exposure of AH130 cells to MMC somewhat inhibited IPN-stimulated activity of adenylate cyclase in contrast with aerobic exposure. Exposure of cells to adriamycin also caused enhancement of IPN-stimulated activity of adenylate cyclase but exposure to nitrogen mustard inhibited the enzyme stimulation by IPN. The enhancing effect of MMC was lost by the combined treatment with α-tocopherol. From these results, it was shown that MMC modulated the activity of adenylate cyclase, probably through alterations in membrane structure.

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