Wagner proposed a new and simple method to predict dosage of drugs obeying simple Michaelis-Menten elimination kinetics. From his theory the following equation, D_n=D_o+1n (C_d/C_o)/S can be derived, which forms the basis of predicting the required dosage (D_n) to obtain a desired steady-state concentration (C_d), using initial steady-state concentration (C_o), obtained with initial dose (D_o) and a population value of S for the drug. We retrospectively investigated the value of S for phenytoin (PHT) in a population of 55 outpatients who had three or more reliable measurements of the steady-state concentration of PHT in serum, measured while they were taking different daily doses. The value of S for PHT was estimated to be 0.0122759 in Japanese patients. The predictive performance of this equation was compared with Bayesian feedback method (B) using retrospective data from 220 outpatients. This equation yielded mean error (ME) of 0.0, mean absolute error (MAE) of 30.7 and root mean squared error (RMSE) of 40.9 mg/d compared to ME of -2.5, MAE of 30.3 and RMSE of 40.1mg/d for B method, These results indicate that this equation may be a useful adjunct for prediction of PHT dosage as well as B method. Moreover, the simplicity of the equation allows calculation on a hand-held calculator.

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The application and usefulness of resealed erythrocytes as a cell carrier of porcine insulin were studied in rabbits. The insulin was loaded in rabbit erythrocytes by a dialysis method followed by isotonic resealing of the erythrocytes at 25 and 37°C. The amounts of insulin entrapped in the erythrocytes at these temperatures were 6.23±1.05 and 5.89±1.33IU/ml of packed cell, with efficiency of encapsulation being 6.0±1.2 and 5.8±2.0%, respectively. When the insulin loaded erythrocytes were incubated in phosphate buffered saline at 37°C, the insulin levels in the resealed cells declined according to a biexponential function. The in vitro stability of the cells resealed at 25°C was superior to that at 37°C. After subcutaneous (s.c.) administration of free insulin, the absorption rate constants in diabetic rabbits were larger than those of normal rabbits. The in vivo decline of insulin released from the loaded erythrocytes indicated a biexponential kinetics. Although the pharmacokinetic behavior of plasma insulin between normal and diabetic rabbits was similar, the hypoglycemic effect was very different between them. These insulin dosings, be they intravenous (i.v.) dosing of insulin or loaded cells or s.c. dosing of insulin, maintained the hypoglycemic effect in diabetic rabbits about twice as long as in a normal animal. Moreover, the effective period of insulin-loaded erythrocytes was longer than that of free insulin dosings. These results suggest that the insulin-loaded erythrocytes may be useful as a dosage form for treatment of patients with diabetes mellitus.

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In order to clarify the utility of resealed erythrocytes as a cell carrier of insulin the freezing stabilities of loaded cells encapsulating two different amounts of insulin (about 0.1 and 7.0 IU/ml of packed cells) were investigated in an anti-freezing reagent containing a high concentration of glycerol at -80°C. After storing for 1 week under the above condition the preparation was thawed at 37°C. Although the osmotic resistance of the loaded cells was lowered more than that of intact cells, the freezing and thawing treatment did not change the resistance of the loaded cells to osmotic shock. Recoveries of hemoglobin from loaded cells with a low insulin content (0.1IU/ml of cells) and the cell volume after freezing and thawing were similar to those from intact cells and the cells resealed without insulin. However, the recovery of insulin from the cells with a high insulin content (7.0IU/ml of cells) was the same as that from one with a low insulin content (about 16%). In the in vitro stability experiment at 37°C the insulin content in the loaded cells decreased according to a biexponential function. The considerable fraction of the loaded cells were lysed by freezing and thawing. In the in vitro stability experiment the decline curve of insulin in the cells showed apparently monoexponential kinetics. From these results, it was established that insulin-loaded erythrocytes may be stored in a high concentration of glycerol under freezing at -80°C, although a partial decrease in the stability of cells was observed after thawing.

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The effect of phenylbutazone (PBZ) on the in vitro binding of sulfadimethoxine (SDM) to serum or albumin was compared among rabbits, dogs and rats. In rabbits, a major metabolite of SDM, N⁴-acetylsulfadimethoxine (N⁴-AcSDM), markedly reduced the in vitro binding of SDM, and PBZ significantly increased the serum concentration of N⁴-AcSDM after SDM administration. PBZ did not affect the in vitro binding of SDM. These findings indicate that in rabbits, PBZ indirectly reduces the in vivo binding of SDM through the interaction of PBZ with N⁴-AcSDM. In dogs, both PBZ and N⁴-AcSDM caused the reduction in the in vitro binding of SDM. However, unlike rabbits, the contribution of N⁴-AcSDM to the in vivo binding of SDM appeared to be negligible in dogs. In rats, PBZ or N⁴-AcSDM had little effect on the in vitro binding of SDM. The co-administration of PBZ significantly increased the total body clearance and steady-state volume of distribution of SDM in rabbits. Such changes in pharmacokinetic behavior were not observed in dogs and rats.

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The effects of cholera and pertussis toxin on the release of noradrenaline (NA) were studied in the rat cerebral cortex. The cerebral cortical slices were incubated with cholera or pertussis toxin for 2 h, subsequently loaded with 1-[³H] NA and superfused continuously. The pretreatment with cholera toxin significantly (p<0.05) enhanced the 20mM KCl-evoked [³H] NA release. In contrast to a significant (p<0.05) increase in [³H] NA release by pertussis toxin, neither A-protomer nor B-oligomer of the toxin could affect the release. These results suggest that cholera and pertussis toxin-substrates, probably guanosine triphosphate-binding proteins, could be involved in the NA release in the central nervous system.

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We have previously reported that (±)-[6]-and (±)-[8]-gingerols potentiate prostaglandin (PG) F_2α-induced muscle contraction, and that other gingerol-related derivatives do not necessarily produce the same effect. The moiety necessary for potentiation was therefore investigated. 1) (±)-[8]-Gingerol potentiated PGF_2α-induced contraction to a greater extent than (±)-[6]-gingerol and (±)-hexahydrocurcumine (HHC), but [6]-shogaol produced inhibition ; 2) Noradrenaline (NA)-induced contraction was inhibited in the following order : [6]-shogaol>(±)-[8]-gingerol>[6]-gingerdione>(±)-[6]-gingerol>S-(+)-[6]-gingerdiacetate (GDA) >[6]-dehydrogingerdione (DHG), whereas (±)-HHC had no significant inhibitory action ; 3) [6]-gingerdione had different effects on PGF_2α-induced contraction, indicating inhibition just after preparation of the solution, no effect apparent after 2 h, and potentiation after 5 h ; 4) [6]-gingerdione showed a change in its chemical structure after 5 h as measured by the FeCl₃ reaction, and ultraviolet and ¹H nuclear magnetic resonance spectra. It was concluded that the aliphatic hydroxyl group present in gingerol derivatives is necessary for potentiation of PGF_2α-and the keto group for inhibition of NA-induced contraction.

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The uptake of CD-349 into the bovine intrapulmonary artery (BPA) and vein (BPV) was examined and characteristics of this newly synthesized 1, 4-dihydropyridine Ca²⁺ antagonist were compared with those of nitrendipine. One hundred minutes after initiation of incubation of the vessels, the uptake of [³H] CD-349 and [³H] nitrendipine reached a plateau. The concentrations of CD-349 inside the muscle cell of the BPA and BPV were 11.1 and 6.8 times higher than that of the incubation medium, respectively, and concentrations of nitrendipine in the BPA and BPV were 8.6 and 6.1 times higher, respectively. The degree of uptake was not influenced by the lowering the incubation temperature nor by adding 2, 4-dinitrophenol. The partition coefficient of CD-349 measured in the corn oil/Ringer and octanol/Ringer systems was greater than the partition coefficient of nitrendipine, independent of the concentration tested. These results suggest that CD-349 permeates smooth muscle membrane by passive diffusion and accumulates inside the muscle cells, much in the same manner as seen with nitrendipine. The lipid solubility of DC-349 presumably accounts for these events.

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The effect of heating on rat liver microsomal glutathione S-transferase activity was investigated. The microsomal glutathione S-transferase activity increased with an elevation of temperature and reached a maximal level at 50°C for 30 min, at which point the enhancement was 2.6-fold. The microsomal glutathione S-transferase activity had one low K_m value for 1-chloro-2, 4-dinitrobenzene at room temperature. However, two K_m values were observed in heated microsomes. N-Ethylmaleimide increased microsomal glutathione S-transferase activity 7.7-fold and a 2.5-fold increase in the activity was observed even after heating of microsomes at 55°C for 10 min. On the other hand, there was no additional activation in the heated-microsomal glutathione S-transferase by glutathione disulfide or diamide with glutathione. The increased activity of the microsomal glutathione S-transferase by heating was not reversed by dithiothreitol. These results indicate that the microsomal glutathione S-transferase activity is activated by heating through a mechanism different from the activation caused by sulfhydryl reagents.

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The effects of phenylethylamine (PEA) and related drugs, such as methamphetamine, phenelzine, methylphenidate, nomifensine and mazindol on the spinal monosynaptic reflex (MSR) were investigated in rats treated with 6-hydroxydopamine (6-OHDA) or 5, 6-dihydroxytryptamine (5, 6-DHT). PEA (1×10^-5mol/kg, i.v.) increased the amplitude of MSR in control rats, but decreased the amplitude in rats treated with 6-OHDA. Although PEA-related drugs increased the amplitude of MSR, they did not change the MSR amplitude in 6-OHDA-treated rats. In 5, 6-DHT-treated rats, PEA-related drugs increased the amplitude of MSR, whereas PEA produced a decrease. These results support our previous suggestion that the enhancement of MSR by these drugs might be mediated through release of noradrenaline or inhibition of noradrenaline uptake at the noradrenergic synapses.

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The optimum conditions of selenium administration to reduce the side effects of a single dose of cis-diamminedichloroplatinum (cis-DDP) in mice were examined. The best effects against lethal toxicity of cis-DDP was obtained when sodium selenite was administered subcutaneously (s.c.) to mice simultaneously with s.c. injected cis-DDP at a molar ratio of 1 to 3.5 (sodium selenite to cis-DDP) on the first day and the same amount of selenite was given daily for four subsequent days. This coadministration of selenite completely depressed not only lethal toxicity of cis-DDP but also its renal toxicity (indicated by increased blood urea nitrogen values) and intestinal toxicity (indicated by the incidence of diarrhea) which were usually observed in the mice treated with cis-DDP alone. Furthermore, coadministration of selenite did not compromise the antitumor activity of cis-DDP against several transplantable tumors in mice. Therefore, the administration schedule of selenite with cis-DDP described above may be useful for cancer chemotherapy.

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