The purpose of present study was to analyze the factors involved in the tissue distribution of vinblastine (VBL). The specific binding of VBL to mouse tissue cytosol determined by a charcoal method correlated well with the tissue concentration of tubulin, a target protein for the pharmacological activity of Vinca alkaloids. The calculated tissue-to-plasma partition coefficients (K_p) in various tissues, based on the VBL binding to 100000×g cytosols showed a good correlation with the corresponding in vivo K_p values of rats reported in the literature, however, the calculated K_p values were greatly underestimated. The total binding (including specific and non-specific bindings) to cytosols from the liver and kidney, determined with the ultrafiltration method, were approximately 5 times higher than those determined with the charcoal method for both tissues. However, the total bindings to cytosol cannot explain the high K_p values in vivo. Considering the intracellular distribution of VBL, it was found that cytosol is not the main binding component for VBL since approximately one-half of the VBL in the liver homogenate was associated with the nuclear fraction. The K_p value in the liver, calculated by considering the intracellular distribution, became close to the in vivo K_p value. It was concluded that the tissue distribution of VBL connot be accounted for only by the binding to tubulin. and that the bindings to other intracellular components should also be included.

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The effect of pentobarbital, which stimulates gastric acid secretion in urethane-anesthetized rats, on secretagogue-stimulated or electrically stimulated acid secretion was studied in the rat perfused stomach. 2-Deoxy-D-glucose (2-DG)-stimulated gastric acid secretion was markedly depressed by intravenous injection of pentobarbital, but was definitely increased by lateral cerebroventricular injection and was unaffected by injection into the fourth cerebroventricle. Bethanechol-stimulated secretion was augmented by intravenous injection of pentobarbital. In vagotomized rats, pentobarbital did not affect the bethanechol-stimulated or electrically vagally stimulated secretion. These findings indicate that pentobarbital produces both stimulatory and inhibitory effects on gastric acid secretion through a central mechanism, especially in the forebrain. It was proposed that the inhibitory response would result from some interaction of intravenous 2-DG and pentobarbital in the central regulatory system of gastric secretion.

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A Na⁺/H⁺ antiporter was solubilized with octyl-β-D-glucopyranoside from rat renal brush border membrane and reconstituted in egg phosphatidylcholine liposomes. The activity of the antiporter was determined by a new method. Reconstitution was performed in a solution containing a pH-sensitive fluorescence dye, fluorescein isothiocyanatc-dextran (FITC-dextran), at pH 5.5. The reconstituted vesicles, encapsulating FITC-dextran, were incubated at pH 8.0, and the intravesicular pH (pH_i) was determined by monitoring fluorescence change of the dye. An increase in the fluorescence intensity which corresponded to an increase in pH_i was observed. The rate of the increase was dependent on the concentration of the extravesicular Na⁺, and the efflux of H⁺ in the presence of 150 mM sodium gluconate was suppressed by the addition of amiloride. These results show that the Na⁺/H⁺ antiporter was functionally reconstituted and that its activity can be determined simply by the use of FITC-dextran.

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The effect of synthetic proteinase inhibitors (PIs) and proteinase substrates on chemotaxis of rat polymorphonuclear leukocytes (PMNs) was studied by using Boyden's method in vitro. Serine-PIs had a potent inhibitory activity on PMN chemotaxis. The relative potencies of the inhibitory action of PIs on the PMN chemotaxis in vitro were TPCK>inhibitor B≥TLCK>EACA hexyl ester>FR 45009. The experiments using serine-proteinase substrates suggest an important role of chymotrypsinlike proteinase of PMNs in the process of PMN chemotaxis. Leupeptin had no direct effect on PMN chemotaxis in vitro, but significantly suppressed the zymosan-mediated generation of a chemoattractant for PMNs in rat serum. Other PIs had no effect on the generation of PMN chemoattractant. These results suggest that the PIs except leupeptin suppress PMN infiltration in vivo as a result of a direct action on PMNs, while leupeptin indirectly suppresses PMN infiltration in vivo through the inhibition of the generation of a chemoattractant for PMNs.

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Secondary lysosomes (argentosomes) were isolated by centrifugation in a discontinuous sucrose density gradient from livers of rats administered colloidal silver. Compared to the crude homogenate, the purities of the argentosome preparations were 17.4-and 18.5-fold in terms of acid phosphatase and N-acetyl-β-glucosaminidase activities, respectively. By lipid analysis, the argentosomes were shown to have intermediate properties between normal lysosomes and tritosomes with regard to the contents of triglyceride and cholesterol. The phospholipid content in the argentosomes was also different from that in these two organelles. The cross-point of argentosomes shifted more to the acidic side than that of normal lysosomes. The data on the binding of tritiated p-biphenylmethyl-(dl-tropyl-α-tropiniun) bromide ([³H] BTTB) to argentosomes indicated that the degree of binding and/or incorporation of this basic compound to the organelles was much higher than that to normal lysosomes. These results suggested that the distribution of BTTB on or within argentosomes might be under the control of the surface charge of the argentosomal membranes.

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The effects of Tween 80 and liposomes on the corneal permeability of dexamethasone (DM) and dexamethasone valerate (DV) were investigated in vitro. A model based on diffusion theory could successfully be applied to analyzing the process by which DM penetrates the cornea from DM preparations. The penetration rate increased according to the concentration of free DM. Although the penetration rate was increased by pretreatment with Tween 80, it was not affected by pretreatment with liposomes. The steroid that penetrated through the cornea from DV preparations had been metabolized to DM. The transfer of DM across the cornea from DV preparations tended to slow down to some extent during the penetration process. Diffusion models were not applicable to this process, in contrast to the corneal penetration of DM from DM preparations. When liposome preparations of DV were applied, the penetration rate of DM across the cornea depended the concentration of free DV in these preparations. When DV aqueous preparations containing different concentrations of Tween 80 were applied, the penetration rate increased as the concentration of the surfactant was increased, even though the concentration of free DV in the suspensions was kept constant. These results suggest that the corneal permeability of anti-inflammatory steroids is not affected by liposomes, but is accelerated by Tweeen 80.

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Penetrations of latamoxef (LMOX) and cefaclor (CCL) into the aqueous humor after intravenous or oral administration were investigated in rabbits. Concentrations of antibiotics in plasma and aqueous humor after administration were determined periodically by microbiological assay. LMOX disappeared from plasma in a monoexponential manner with a half-life of 43 min after intravenous administraiton at a dose of 50 mg/kg. The maximum concentration of LMOX in aqueous humor (6.4 μg/ml) was observed 1 h after administration. When CCL was administered orally at a dose of 50 mg/kg, the maximum concentration of CCL in aqueous humor was 1.00 μg/ml 1.5 h after administration, whereas the maximum plasma concentration of 19.2 μg/ml was observed at 30 min. Pharmacokinetic analysis (simultaneous simulation) of plasma and aqueous humor concentration-time courses was made using the best fitted compartment model examined (modified two-compartment model). Prediction of the concentration of antibiotics in aqueous humor from the plasma concentration profile was also examined using the same compartment model in a separate experiment. The predicted concentration in aqueous humor was proved to coincide reasonably well with the measured concentration.

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The lymphatic transport of recombinant human tumor necrosis factor (rHu-TNF) was investigated after its administration via various routes in anesthetized rats. After intravenous (i.v.) administration, the level of rHu-TNF in the lymph reached a peak at 2 h, and thereafter decreased exponentially in a pattern similar to that of the elimination from plasma. Intramuscular (i.m.) and subcutaneous (s.c.) administrations resulted in low levels of rHu-TNF both in the plasma and in the lymph. On the other hand, intraperitoneal (i.p.), intra-stomach wall (s.w.) and intra-gut wall (g.w.) administrations gave high lymph levels of rHu-TNF. After the s.w., g.w. and i.p. administrations, the ratios of rHu-TNF recovered from the thoracic duct to the cumulative amount estimated from the rHu-TNF concentration in plasma were about 25, 32 and 8 times higher than in the case of i.v. administration, respectively. These results suggest that the routes of local administration of rHu-TNF such as s.w., g.w. and i.p. may be highly effective for the treatment of lymphatic metastasis of cancer.

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To investigate the influence of diabetes on the responsiveness of the cardiovascular system, we have examined the effects of various agents on the reactivity of the vascular smooth muscle of aortic strips obtained from age-matched control and diabetic rats. Norepinephrine (NE) contracted the aortic strips obtained from age-matched control and diabetic rats in a concentration-dependent manner, but maximal contraction of aortic strips in response to NE was enhanced in diabetic rats. The EC₅₀ value for NE in the diabetic aortic strips was similar to that in the aorta from age-matched controls. Ca-induced contracture of the aortic strips which were depolarized with isotonic K⁺ (60 mM) was potentiated in aortic strips from diabetic rats, when compared with those from age-matched controls. Ca-induced contracture of aortic strips, preincubated with 10^-6M NE and 10^-6M nicardipine in Ca²⁺-free Krebs-Henseleit solution (KHS), was not significantly different in age-matched control and diabetic rats. Bay K 8644, an activator of calcium channels, produced an increase in the force of contraction of the slightly depolarized aorta from diabetic rats. Phasic contraction induced by phenylephrine (PE) in the presence of 10^-6M nicardipine in Ca²⁺-free KHS was significantly enhanced in aortic strips obtained from diabetic rats. These results demonstrate that NE-induced contraction of the aortic strips obtained from diabetic rats was significantly enhanced, and that this increased contractile response of the aorta to NE may be due to an increased influx of extracellular calcium through the voltage-dependent Ca²⁺ channels, but not through the receptor-operated Ca²⁺ channels. Furthermore, this enhanced response may be responsible for an increased rate of turnover of phosphatidylinositol.

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