The dose-dependent first-pass hepatic metabolism and pharmacokinetics of 4-methylumbelliferone (4-MU) were studied at four dose levels (17.6μg-5.29 mg) in rats. 4-MU was given intravenously and intraportally to determine the availability of 4-MU. The availability increased from 0.18 to 1.31 when the dose was increased from 17.6 μg to 5.29 mg/rat. The total body plasma clearance of 4-MU was accounted for mostly by the hepatic conjugative metabolism. The contribution of renal clearance to total plasma clearance was 11-35%, depending on the dose. The marked dose-dependency of availability may thus be explained by the saturable conjugative metabolism of 4-MU.

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We attempted to determine whether there is a possible link between the effect of papaverine on p-aminohippurate (PAH) accumulation, on cyclic nucleotide content and on certain other cellular functional parameters in rat kidney cortical slices in vitro. Papaverine at a concentration of 0.1 mM almost completely inhibited PAH accumulation in the slices. However, cyclic guanosine 3', 5'-monophosphate (cyclic GMP) and cyclic adenosine 3', 5'- monophosphate (cyclic AMP) levels in the slices were not significantly affected by papaverine at 0.1 mM, though papaverine at a concentration of 1 mM increased the cyclic GMP level without affecting the cyclic AMP level. Papaverine (0.1 mM) produced a decrease in the sodium gradient and in the adenosine triphosphate (ATP) level in the slices. Calcium uptake by mitochondria, isolated from kidney cortex, was apparently decreased in the presence of 0.1 mM papaverine. These results suggest that the inhibition of phosphodiesterase probably does not explain the action of papaverine on PAH accumulation to the slices. The inhibition of PAH accumulation by papaverine is partly a reflection of the fall in the sodium gradient in the slices created with papaverine. In addition, a depression of ATP level in the slices and an inhibition of mitochondrial calcium uptake may be related to a possible mechanism of action of papaverine on PAH accumulation.

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Serum concentration-time courses of quinidine in humans were predicted by a physiologically based pharmacokinetic model developed from the rat using reported values for the serum protein binding, blood-to-serum concentration ratio, renal clearance and physiological constants, i.e. tissue volume and blood flow rate of each tissue. The tissue binding parameters of the rat were used for humans. The hepatic intrinsic clearance (CL_{H, int}) of quinidine for human was extrapolated by using the relation between CL_{H, int} of humans and those of the rat reported for antipyrine, phenytoin and hexobarbital. The predicted time course were comparable with the observed data in humans obtained from the literature, though slight differences were shown in the half-lives between the observed data and the predicted curves. It was suggested that the overestimation of the tissue binding parameters might be the cause of this difference.

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An in situ experimental model of rectal absorption was studied in rabbits compared with in vivo determination of drug concentration in the plasma of postcaval vein using indomethacin as drug. Pharmacokinetic parameters were similar between in vivo and in situ. When results from both studies were compared, 60% of the drug administered to the rectum was absorbed from the superior hemorrhoidal vein and the remaining 40% was absorbed from the inferior hemorrhoidal vein. When an aspirin suppository was used in this model, the amount of unaltered aspirin absorbed in the rectal mucosa or space was greater than the absorbed salicylic acid which was metabolized or degradated from aspirin. In the case of insulin, these differences were not seen in the insulin concentration of venous plasma between insulin physiological saline and surfactant suspension. However, using the in situ model, the surfactant effect on rectal absorption of insulin was observed. From the above results, it was concluded that this in situ experimental model of rectal absorption has advantages in that it can be used directly to measure the rectal absorption rate and to determine ratios of easily metabolized and poorly absorbed drugs. Therefore, this model appears to be useful in evaluation of rectal absorption.

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We studied the effects of pinacidil on renal hemodynamics and function in anesthetized dogs. An intravenous injection of pinacidil, at a dose of 0.25 mg/kg, resulted in a rapid and marked reduction of the mean systemic blood pressure (MSBP) accompanied by a significant increase in renal blood flow (RBF). There were no significant changes in glomerular filtration rate (GFR), urine flow (UF) and urinary excretion of electrolytes (UEE). When pinacidil was administered at a dose of 0.5 mg/kg, the hypotensive effect was more potent. RBF did not change, but GFR, UF and UEE significantly decreased. These antidiuretic effects were not influenced by renal denervation. Hydralazine, at doses of 0.5 and 2.0 mg/kg, caused a significant and sustained reduction of MSBP, but the effects were much less potent than those seen with pinacidil. A sustained increase in RBF was observed after hydralazine at both doses. The lower dose elicited increases in UF and UEE, although the GFR remained unchanged. The higher dose of hydralazine caused a reduction of GFR, accompanied by decreases in UF ancT UEE. These antidiuretic effects were abolished by renal denervation. Intravenous injection of pinacidil or hydralazine produced a significant increase in the renin secretion rate. Intrarenal arterial infusion of pinacidil (2.0 μg/kg/min) produced a more marked diuretic effect than hydralazine (20 μg/kg/min). These findings indicated that the hypotensive activity of pinacidil is more potent than that of hydralazine, and suggested that the antidiuretic action of i.v. pinacidil (0.5 mg/kg) is due to a reduction of renal perfusion pressure. Furthermore, this drug may exert an additional action in the kidney to cause diuresis.

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The absorption and lymphatic delivery of a new immunosuppressive drug, cyclosporin A (CsA), with the aid of lipid surfactant mixed micelles (MM) system using different administration routes were studied in the thoracic duct cannulated rat model at a dose level of 7 mg/kg. The rectal or intraperitoneal (i.p.) administration of CsA indicated a small amount of CsA in the plasma and in the lymph for 6 h. As oral routes, intrastomach (i.s.) and intraduodenal (i.d.) administration of CsA were performed and high lymph CsA levels were obtained. The i.s. administration of CsA resulted in the highest CsA levels in the lymph, 16 μg/ml, about twenty times higher than the rectal or i.p. administration. These results strongly support the usefulness of an oral CsA dosage form for the selective lymphatic delivery of CsA in clinical immunosuppressive therapy by means of a new mixed micelles system.

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One of the so-called LC components, the content of which is increased in the serum of PSK (antitumor polysaccharide) treated mice, was purified by repeated ionexchange column chromatography on DEAE-Sephadex A-50. The purified protein, designated as LC-2, was identified as a variant of mouse transferrin, which is a serum β₁-globulin having an iron-binding capacity. The absorption spectrum and ultraviolet circular dichroism (CD) curve of LC-2 were identical with those of mouse transferrin. The molecular weight, isoelectric point and amino acid composition of LC-2 were in good agreement with the results obtained previously for mouse transferrin. However, the carbohydrate content of LC-2 was different from that of mouse transferrin. This protein restored the depressed spleen cell response of tumor-bearing mice to concanavalin A (Con A) and promoted the metabolism of proteose-peptone induced peritoneal macrophages obtained from tumor-bearing mice. Furthermore, it had weak but definite antitumor activity against Sarcoma 180 cells in vivo.

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A potent platelet antiaggregant action of an antiarrhythmic peptide (AAP) was demonstrated to be a cause of the antithrombotic effect. AAP (10, 20 or 40 mg/kg, i. v.) inhibited ex vivo platelet aggregation induced by collagen in a dose-dependent manner. AAP also inhibited the platelet aggregation of platelet-rich plasma (PRP) induced by collagen, Ca-ionophore A-23187, adenosine diphosphate (ADP), thrombin or arachidonic acid in vitro. The IC₅₀ was 2.5 mM for collagen 1.7 mM for A-23187, 5 mM for ADP, 0.4 mM for thrombin and 0.15 mM for arachidonic acid. The aggregation inhibitory activity of the peptide on washed platelet (WP), in a Ca²⁺-free medium, was stronger than on PRP. The IC₅₀ was 1 mM for collagen and 20 μM for A-23187. No significant difference was found between antiaggregant activities of platelet-free plasma (PFP) from AAP-treated rats and PFP from normal rats supplemented with AAP. The direct action of AAP on platelets was also supported by the incorporation of AAP into platelet cytoplasma which caused a decrease of Ca²⁺-dependent 3' : 5'-cyclic nucleotide phosphodiesterase (Ca-PDE) activity. It was considered that AAP showed its platelet aggregation inhibitory activity by decreasing intracellular Ca²⁺ concentration through the inhibition of Ca-PDE activity.

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The combined effects of Shosaikoto, one of the Kampohozai (Chinese traditional medicine), and prednisolone were examined for suppressive actions on pituitary adrenocortical axis function and immune response induced by prednisolone using rats and mice. The administration of Shosaikoto, 1.2 g/kg p.o., for 45 d showed a tendency to increase adrenal weight. By the combined use of Shosaikoto, 0.12 and 1.2 g/kg p.o., and prednisolone, 0.016 g/kg p.o., for 45 d, the decrease of adrenal weight induced by the treatment with prednisolone was restored. The administration of Shosaikoto, 1.2 g/kg p.o., elevated the blood corticosterone level. In the case of combined use, Shosaikoto, 0.12 and 1.2 g/kg p.o., inhibited the decrease of blood corticosterone level induced by the treatment with prednisolone, 0.004 g/kg p.o., and Shosaikoto, 1.2 g/kg p.o., inhibited the decrease of blood corticosterone level induced by the treatment with prednisolone, 0.016 g/kg p.o. On the other hand, the administration of Shosaikoto, 1.2 g/kg p.o., for 7 d reduced the number of hemolytic plaque forming cells (HPFC) in spleen cells. But, Shosaikoto, 1.2 g/kg p.o., administered for 7 d inhibited the decrease of the number of HPFC induced by the treatment with prednisolone, 0.01 and 0.03 g/kg s.c., for 3 d. Furthermore, Shosaikoto, 1.2 g/kg p.o., restored the number of rosette forming cell (RFC) which decreased by prednisolone, 0.03 g/kg s.c. The decrease of 7S HA titer of the serum by the treatment with prednisolone, 0.01 g/kg s.c., was also inhibited by the combination with Shosaikoto, 1.2 g/kg p.o.

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The role of mandibular striated duct in salivary excretion of endogenous urea was studied by a technique of retrograde ductal injection of HgCl₂ and a stop flow analysis. (1) It was verified in this study that treatment with HgCl₂ markedly inhibited Na⁺ reabsorption in the striated duct so that water reabsorption driven by the Na⁺ reabsorption would be inhibited substantially. (2) The saliva/plasma concentration ratios (S/P ratios) of urea in HgCl₂-treated saliva (about 0.71) were significantly higher than those in untreated saliva (about 0.37). (3) The excretion rate of urea in HgCl₂-treated saliva (about 0.02 mg/min/kg) was also significantly higher than those in untreated saliva (about 0.01 mg/min/kg) despite the same flow rate for both saliva samples. Furthermore, (4) The S/P ratios of urea in the second (0.25 - 0.50 ml) poststop-flow saliva (about 0.65) were significantly higher than those in prestop-flow saliva (about 0.35). These results suggest a possibility that salivary urea is reabsorbed in the dog mandibular striated duct and that the enhancement of the S/P ratio as well as the salivary level of urea by the pre-treatment with HgCl₂ may be due to the inhibition of urea reabsorption.

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Neplanocin A is a cyclopentenyl analog of adenosine which has been isolated from the culture filtrate of Ampullariella reqularis. Antitumor activity of twenty three derivatives of neplanocin A was examined against L1210, sarcoma 180 and L5178Y. Neplanocin A showed a marked inhibition of growth of L1210 in vivo. Other derivatives which had a 2' or 3'-substituted cyclopentene group showed weak cytotoxicity against L5178Y cells in vitro. Neplanocin A inhibited the biosynthesis of ribonucleic acid (RNA) and protein, while 6-chloroneplanocin A, a new active derivative, showed a specfic inhibition of only RNA synthesis. The two hydroxy groups in the cyclopentene moiety with a ribose type structure are important for marked antitumor activity.

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An investigation on the effect of heparin on leukocytes in vitro was conducted. We have demonstrated that heparin and other mucopolysaccharides destroyed leukocytes as judged by macromolecule leakage. The cytotoxicity of heparin was suppressed by protamine. A medium which mimics intracellular ionic conditions was found to suppress the cytotoxicity of heparin. Macromolecule leakage induced by heparin is thought to be facilitated by passive ion flux. Mepacrine, a phospholipase inhibitor, suppressed the heparin-induced macromolecule leakage from leukocytes. Thus, the activation of phospholipase appears to be involved in the cytotoxicity of heparin. These results suggest that activation of phospholipase and passive movement of ions may be important steps for the heparin-induced leukocyte lysis in vitro.

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The uneven distribution of the glucuronidation and sulfation activity of acetaminophen (APAP) and p-nitrophenol (PNP) in liver was studied using centrilobular and periportal regions of isolated rat hepatocytes obtained by Percoll density gradient centrifugation, in a manner similar to that for harmol reported previously. The glucuronidation of APAP and PNP occurred predominantly in the periportal region. Glucuronidation activity of APAP in the centrilobular region was not detected. This finding may reflect the existence of different forms of uridine diphosphate-glucuronyltransferase (UDPGT) for APAP and PNP. The regional difference in K_m values was observed for PNP, but not for harmol as reported in the previous paper. This suggests the existence of multiple forms of UDPGT for PNP as well as the heterogeneous distribution of this enzyme in liver lobules. The sulfation rates of APAP and PNP in the centrilobular region were smaller than those in the periportal region. The regional difference of APAP sulfation was due to different V_max values. As shown in the harmol experiment, the predominant distribution of sulfation activity of APAP and PNP in the periportal region agreed with the results in the perfused liver previously reported by other investigators but that of glucuronidation activity was at variance with them.

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