Shozo Muranishi

Mitomycin C‐dextran conjugate: a novel high molecular weight pro‐drug of mitomycin C

A high molecular weight derivative of mitomycin C (MMC), mitomycin C‐dextran conjugate (MMC‐D) has been synthesized and its biological and pharmacological properties investigated. MMC is released from MMC‐D in vitro with a half‐life of 24 h. After intraperitoneal injection of MMC‐D, free MMC could be detected in plasma and urine of mouse for 5–8 h, while MMC administered as a free form was eliminated rapidly. After MMC‐D, given to mice bearing Ehrlich ascites carcinoma or B16 melanoma there was a reduction in toxicity and an increase in survival time compared with MMC. These observations suggest that the high molecular weight MMC‐dextran derivative is a kind of pro‐drug which persists in the body giving a sustained release of free MMC thus significantly increasing the antitumour activity of the parent drug.

Effect of fatty acids and monoglycerides on permeability of lipid bilayer

The effect of fatty acids and monoglycerides on barrier properties of liposomal membranes prepared from egg phosphatidylcholine was investigated. The incorporation of these lipids as liposomal membrane components induced the alteration of the permeability to less permeable liposomally entrapped drugs, sulfanilic acid and procainamide ethobromide (PAEB). Monoolein caused greatly increased permeability of both drugs and unsaturated fatty acids markedly enhanced the release rate of PAEB, while saturated fatty acids caused a small increase in the release rate. Electron spin resonance (ESR) investigation with 5-nitroxide stearic acid showed that fatty acids disordered the hydrophobic region of the lipid bilayer and the disordering effect of unsaturated fatty acids was greater than that of saturated ones. It was demonstrated that the incorporated fatty acids and monoglycerides interacted with the polar region of the membranes by ESR study with cholestane label and 1H-NMR study. These results indicated that the increase in the membrane permeability caused by fatty acids and monoglycerides associated with the disorder in the membranes interior and the interaction of the incorporated lipid with the polar head group of phospholipid.

Enhanced intestinal permeability to macromolecules II. Improvement of the large intestinal absorption of heparin by lipid-surfactant mixed micelles in rat☆☆☆

Abstract The effect of lipid-surfactant mixed micelles on the intestinal absorption of herapin was investigated in the loop of large intestine of rats. It was observed that large intestinal absorption of heparin was essentially very small in the absence of adjuvants. Monoolein-taurocholate, oleic acid-taurocholate and oleic acid-HCO 60 mixed micellar solutions promoted a remarkable absorption of heparin, whereas the surfactant micellar solutions alone did not enhance its absorption. The promoting effect of monoolein-taurocholate mixed micelles in the large intestine was larger than that in the small intestine, and the minimum concentration of the mixed micelles to produce the potentiation of absorption was approximately one-fourth of that required in the small intestine. The effect of monoolein or oleic acid incorporated in micellar solution on the absorption inducement of heparin and the concomitant movement of these lipids suggest that lipids play a critical role in the improvement of absorption of macromolecules.

Role of intramuscular administration of water-in-oil emulsions as a method for increasing the delivery of anticancer to regional lymphatics

Further work was undertaken to clarify the mechanism of enhanced delivery of anticancer agents into rat lymph nodes by water-in-oil (W/O) emulsions. Radiolabeled [131I] iodohippuric acid (IH, watersoluble model compound) and [14C]tripalmitin (TP, tracer of oil) were administered intramuscularly, and radioactive concentrations in blood, lymph nodes, and muscles were determined. Also, a new type of emulsion, gelatin-containing W/O (W/O-G) emulsion, was manufactured to be used as a delivery system for the anticancer agents. It was found that the rate of transfer of TP into lymph nodes was enhanced in the following order: oil, oil-in-water (O/W) emulsion, W/O emulsion, and W/O-G emulsion. The transfer of IH into lymph nodes was enhanced more effectively by W/O-G emulsion. The results of this study suggest the existence of a special transport mechanism through which drug and oil are delivered together.

An application of water-in-oil and gelatin-microsphere-in-oil emulsions to specific delivery of anticancer agent into stomach lymphatics.

The efficiency of water-in-oil (W/O) and gelatin-microsphere-in-oil (W/O-G) emulsions as drug delivery systems for achieving specificity into lymphatics was evaluated in the rat stomach. Following injection into the stomach wall, radioactivities of131I-labeled o-iodohippuric acid (IH, watersoluble model compound) and [14C]tripalmitin (TP, tracer of oil) in blood, regional lymph nodes, thoracic lymph, and stomach were determined. Since increased transfer of TP indicated the facilitation of lymphatic transport of IH following injection of W/O and W/O-G emulsions, the existence of a special transport mechanism through which drug and oil are delivered together was confirmed for this injection site. W/O and W/O-G emulsions increased the concentration-time curve (AUC) of IH in the regional lymph nodes (1.7 and 5.5 times that of aqueous solution injection, respectively), so the improvement of bioavailability was accomplished. In addition, a prolonged release of IH and decrease of its maximum blood concentration were obtained following injection of W/O-G emulsion. These results suggest that W/O and W/O-G emulsions satisfy many of the criteria of an ideal drug delivery system for cancer chemotherapy. An abundant supply of lymphatic vessels in the stomach wall exhibited the efficiency of these delivery systems more clearly than did thigh muscle.

The absorption from the gut of quinine and chlorpheniramine given with various anionic agents

The absorption of quinine and chlorpheniramine with anionic agents was examined in the rat rectum, small intestine and stomach. The enhancement of absorption was related to partition behaviour, to the organic solvent, and surface activity of ion‐pair complexes, but it seems that with results from these properties alone it is not possible to explain the apparent increase in the in situ absorption of amines. In the presence of anionic agents, the absorption of amines was enhanced at all sites examined and kinetically the uptake to the mucosal membrane was increased in the rectum and small intestine. The effect of anionic agents on the uptake of amines was greater in the rectum than in the small intestine and this may be related to differences in the nature of the gut wall.

Catalytic effect of cationic surfactants on degradation of cephalexin in aqueous solution.

Penicillins and cephalosporins have been known to undergo remarkably facile cleavage of their @-lactam bonds. Recently, Yamana & Tsuji (1976) reported the kinetics of the hydrolysis of six therapeutically useful cephalosporins. They showed the pH-rate profile of the degradation of cephalexin. Cephalexin is fairly acid stable and much more susceptible to hydroxide-ion catalysed degradation. At neutral pH, its degradation involves intramolecular-nucleophilic attack of the sidechain or-amino group on the ,8-lactam carbonyls. On the other hand, vigorous interest has been shown in the kinetics and mechanisms of organic reactions which occur in the presence of surface-active agents (Fendler & Fendler, 1970). The interactions between the substrate and the specifically oriented hydrophobic and hydrophilic parts of the micelle are chiefly responsible for the spectacular rate enhancements or inhibitions exhibited by micelles on organic reactions. We found that the degradation of cephalexin was subject to marked catalysis by hexadecyltrimethylammonium bromide (CTAB). We have investigated some of the characteristics of the degradation of cephalexin in the presence. of CTAB. Hydrolysis of cephalexin was at 37 and ionic strength 0.25 by using appropriate buffer systems. The rate of hydrolysis was determined by iodometric titration (Finholt, Jurgensen & Kristiansen, 1965) and/or by measuring the loss of the characteristic ultraviolet absorbance at 261 nm due to the 8-lactam bond. Good first order plots were obtained and the pseudo-firstorder rate constants were determined. The pseudo-first-order rate constant for the degradation of cephalexin in the absence of surfactant, k,, was 0.0450 h- at pH 6 3 . Its range of concentrations was 0.05-10m~ and in this range the observed rate constants did not vary, within the limits of experimental error, as a function of substrate concentration. The observed rate constants, k+, for the degradation of cephalexin at pH 6.5 in the presence of various additives are shown in Table 1. In the presence of cationic surfactants such as CTAB and benzalkonium chloride above their critical micelle concentrations (cmc), the degradation of cephalexin increased by a factor of about 9 to 14. On the contrary, in the presence of anionic surfactant, sodium lauryl sulphate (SLS), the degradation of cephalexin was slightly protected. Positively charged tetraethylammonium chloride did not alter the degradation of cephalexin. Consequently, it appears that the enhancement of the degradation of cephalexin is a specific effect of cationic micelles. * Correspondence. Table 1. Effect of various additives on the stabitit,, o/ cephalexin at p H 6.5, 37 and p = 0.25.

Black lipid membranes as a model for intestinal absorption of drugs.

Black lipid membranes were generated in isotonic buffer (pH 4·5 and pH 6·5) from egg phosphatidylcholine and intestinal lipid, and the permeability to salicylamide, salicylic acid, p‐aminobenzoic acid and tryptophan of these membranes was studied. Electrical resistance of intestinal lipid membranes was higher than that of phosphatidylcholine membranes. The presence of cholesterol produced an increase in the electrical resistance of black lipid membranes and a small decrease in the permeability of membranes to drugs. The permeability coefficient of salicylamide, an uncharged drug, was much larger than the coefficients of the charged drugs examined. The values for salicylic acid and p‐aminobenzoic acid were much larger than comparable values predicted from their partition coefficients. Intestinal lipid membranes were more permeable to acidic drugs than phosphatidylcholine membranes. It is suggested that phospholipids and other lipid components of the small intestine may play an important role in the membrane permeability to acidic drugs. This method may be of interest in studying the complex processes of drug absorption from intestine.

Pharmacokinetics of the hepatobiliary transport of bromphenol blue as a model of organic anionic compounds

A new pharmacokinetic model is proposed to explain the hepatobiliary transport of a nonmetabolized sulfonic acid dye, bromphenol blue, which is actively transported from the bloodstream into bile. This model has the advantage of taking into account the roles of the liver cytoplasmic Y- and Z- binding proteins and T binder.

The photodynamic action of riboflavine on erythrocytes

Abstract The photodynamic action of riboflavine and riboflavine phosphate on erythrocytes was studied. It was found that irradiation of rat erythrocyte suspension in the presence of riboflavine phosphate resulted in an enhancement in erythrocyte potassium losses. Also, in the presence of riboflavine and light the release of lactose isonicotinoyl-hydrazone entrapped in released mouse erythrocytes, was markedly increased. The delayed photosensitizing effect, after keeping the irradiated samples for 20 hours in the dark, was more pronounced. No significant photohemolysis of erythrocytes could be demonstrated. Products of lipid peroxidation were formed, and was assumed to be responsible for the alteration in membrane permeability.