Male Donryu Rats Research Articles

Colonization of H. Pylori in the stomach of rats with acetic acid-induced ulcers: Effects of antibiotics and acid pump inhibitors

It is generally believed that H. pylori cannot colonize the stomachs of normal rats. We examined the potential H. pylori colonization in the stomachs of rats with or without chronic ulcers and the effects of antibiotic drugs and acid pump inhibitors on H. pylori viability and ulcer healing. [Methods] Ulcers were produced by acetic acid (20%, 0.04ml) injection into the stomachs of male Donryu rats (7-wk-old). All rats were orally inoculated once with H. pylori (ATCC43504, 3 X 108CFU/rat). 2, 4, 6, 8 and 10 wk after the inoculation, the animals were killed and then H. pylori viability, ulcerated area, and rnyeloperoxidase (MPO) activity in the gastric mucosa were determined. Clarithromycin (CAM, 20, 40, 80mg/kg), amoxiciUin (AMX, 1, 3, 5mg/kg), metronidazole (MTR, 5 mg/kg), omeprazole (OME, 30mg/kg), leminoprazole (LEM, 80mg/kg), CAM+OME or CAM+LEM was orally administered for 1 or 2 wk. [Results] A single inoculation of 1-1, pylori could not colonize the intact rat stomach, ie., no ulcers. Even under complete suppression of gastric acid with omeprazole, no colonizatin was observed in the normal rats. In contrast, H. pylori did colonize the ulcerated stomach for up to 10 wk at an incidence > 80%; 1.2 x 105CFU/rat. MPO activity was significantly elevated in the gastric mucosa with ulcer (608.1 +-81.0 vs. 364.9 +46.4 pMH202/min in the 1-1. pylori non-infected group). CAM (2wk), AMX and MTR (lwk) significantly and dose-dependently eradicated H. pylori. While AMX and MTR had insignificant effect on ulcer healing, CAM at > 40mgkg significantly delayed ulcer healing. In contrast, OME and LEM tended to enhance ulcer healing. However, they significantly prevented the delay in ulcer healing caused by CAM. [Conclusion] H. pylori was unable to colonize the intact stomach of rats, but did colonize the stomach with ulcers. CAM significantly eradicated H. pylori, but delayed ulcer healing which was significantly prevented with acid pump inhibitors.

Thermoeffector thresholds and preferred ambient temperatures of the FOK rat.

The FOK is an inbred rat strain with a genotypic adaptation to hot environments. The present study compared the thermoeffector thresholds and preferred ambient temperatures (Tpref) of the FOK rat with those of other rat strains. Male FOK, WKAH, and Donryu rats were used. First, they were loosely restrained and placed individually in a metabolic chamber with an ambient temperature of 26.0 degrees C. Their hypothalamic temperature (T(hy)), tail skin temperature (Tsk), and heat production (M) were measured. After thermal equilibrium had been attained, the rats were gradually warmed and then cooled using an intravenous thermode. The threshold T(hy) values for tail skin vasodilation and cold-induced thermogenesis were defined as the points at which sharp increases in Tsk and M occurred, respectively. The two thresholds of the FOK rat were lower than those of the WKAH and Donryu rats. In a second set of experiments, the FOK and WKAH rats were placed individually in a thermocline. Their intra-abdominal temperatures (T(ab)) were measured by a biotelemetry system, and the rats' Tpref values were estimated with the thermal gradient. Mean T(ab) and Tpref over a 24-h period for the FOK rat were significantly lower than those of the WKAH rat. The results suggest that in the FOK rat the control ranges of autonomic and behavioral thermoregulation are lower than those of the other rat strains examined. This contributes to the maintenance of core temperature at low levels.

Remodeling of capillary network in left ventricular subendocardial tissues induced by intravenous vasopressin administration.

The question of whether the coronary vasospasm induced by intravenous administration of vasopressin produces any remodeling of the capillary network in the left ventricle was investigated. To this end, cardiac tissues obtained from vasopressin-injected rats were stained to allow capillary counting and for basic fibroblast growth factor (bFGF). Nine male Donryu rats were divided into three groups that received, respectively, 0.25 ml of saline containing 0, 0.5, or 1.0 U/kg vasopressin injected into the tail vein once daily for 4 days. Rats were killed 30 days after the last injection. Two additional rats each received a single intravenous injection of 1.0 U/kg vasopressin and were killed 24 hours later. The left ventricles were removed and 16- or 10-micron frozen sections were cut for differential staining and distribution of bFGF, respectively. Differential staining was used to classify the capillary portions, and bFGF was identified by immunohistological staining. Compared with the control group, total capillary density was increased in both vasopressin-treated groups, capillary to myocyte ratio was increased, and the capillary domain areas decreased in the three capillary portions. Arteriolar and intermediate capillary portions increased, while the venular capillary portion decreased. In rats killed 24 hours after vasopressin injection, a considerable amount of bFGF could be demonstrated immunohistochemically in the ventricular tissues, and the punctate distribution of bFGF was still found in rats killed 30 days after treatment. A remodeling of capillary network which would increase the oxygen transport capacity to cardiac tissues was produced in left ventricular tissues by intravenous injection of vasopressin. bFGF located around capillaries and in the interstitial space may have been involved in the capillary remodeling.

Glutamine and arginine metabolism in tumor-bearing rats receiving total parenteral nutrition

Arginine supplementation increases glutamine levels in muscle and plasma. Since glutamine production is increased in catabolic states, these observations prompted us to investigate whether the flux of arginine to glutamine was increased in tumor-bearing (TB) rats, and we measured the synthesis rate of glutamine from arginine in control versus TB rats receiving standard total parenteral nutrition (TPN) solution. Male Donryu rats (N = 36; body weight, 200 to 225 g) were divided into two groups, control and TB rats. Yoshida sarcoma cells (1 × 10 6) were inoculated into the back of the rats (n = 18) subcutaneously on day 0. The rats were given free access to water and rat chow. On day 5, all animals, including non-TB rats (n = 18), were catheterized at the jugular vein and TPN was begun. On day 10, TPN solution containing either U- 14C-glutamine (2.0 μCi/h) or U- 14C-arginine (2.0 μCi/h) was infused as a 6-hour constant infusion. At the end of the isotope infusion, plasma was collected to determine the glutamine production rate in rats receiving U- 14C-glutamine, and the ratio of specific activity of glutamine to specific activity of arginine was measured in rats receiving U- 14C-arginine. Only 2 g tumor caused a decrease in glutamine levels and an increase in glutamine and arginine production. The low flux rate of arginine to glutamine was observed in control rats (Arg to Gln, 41.0 ± 11.9 μmol/kg/h). On the other hand, TB caused a significant increase in Arg to Gln compared with the control (213.3 ± 66.1 μmol/kg/h, P < .01 v control). An increase in the flux rate of Arg to Gln was associated with an enhancement in the ratio of specific activity of ornithine to specific activity of arginine in TB rats (control 51.5% ± 10.9% v 77.4% ± 8.9%, P < .05). We conclude that (1) glutamine and arginine metabolism is altered with very small tumors, (2) although the flux of Arg to Gln was increased in TB and rats, the small increase in Arg to Gln cannot explain the observed large increase in Gln production.

A new model of delayed healing of acetic acid ulcers in rats by indomethacin via osmotic pump

Gastric ulcers were produced in male Donryu rats (8-weeks-old) by subserosal injection of 20 microliters of 20% acetic acid. Five days later, an indomethacin (IND)-filled osmotic pump (OP) was implanted into the dorsal subcutaneous space in the rats and maintained for 2, 3 or 4 weeks. The natural healing of the acetic acid-induced ulcers was significantly (P < 0.05) delayed by administration of IND via OP implanted for 4 weeks. Two, 3 and 4 weeks after OP implantation, the plasma IND levels was 1.87 +/- 0.13, 2.43 +/- 0.16 and 0.74 +/- 0.26 (micrograms/ml), respectively, showing that a steady state IND plasma level was maintained for 3 weeks. The gastric mucosal PGE2 levels in rats with ulcers for 3 weeks after implantation of OP were significantly (P < 0.05) reduced by IND (IND(-):576.6 +/- 83.9 pg/mg, IND(+):355.6 +/- 34.7 pg/mg). Repeated administration of enprostil, famotidine and rabeprazole at 25 micrograms/kg, 100 mg/kg and 10 mg/kg (p.o., b.i.d.), respectively, showed anti-ulcer activity. Teprenone and rebamipide had only slight anti-ulcer activity. These findings indicated that this model of delayed healing of acetic acid ulcers by IND using OP is useful for investigating the anti-ulcer activity of drugs.

Cathepsin B in the growth of colorectal cancer: suppressive effect of leupeptin on the growth of DMH-induced rat colon neoplasm.

Cathepsin B, a thiol protease, has been reported to be involved in cancer progression and metastasis. The suppressive effects of two kinds of protease inhibitors, leupeptin and dietary camostate (FOY-305), on tumorigenesis and progression in 1, 2-dimethylhydrazine (DMH)-induced rat colon neoplasm were examined in relation to tissue cathepsin B activity. Male Donryu rats were treated with leupeptin or FOY-305 during or after the administration of DMH. There were no significant differences in average tumor numbers among all DMH-treated groups. However, the percentage of small tumors was significantly higher in the group in which leupeptin was supplied during DMH administration. This trend was not recognized in the FOY-305-treated groups. The ratio of cathepsin B activity in the tumors to that in the tumor-bearing tissue (T/Tb) was significantly increased with increasing tumor size (P = 0.009). The cathepsin B activity levels in the tumor-bearing mucosa in the groups which received leupeptin or FOY-305 following DMH treatment were both significantly lower than that in the group which received neither protease inhibitor (P = 0.046 and P = 0.0067, respectively). The results obtained indicate that leupeptin may have suppressed tumor growth by lowering the tissue cathepsin B activity.

Oral Supplementation with Branched-Chain Amino Acids Improves Transthyretin Turnover in Rats with Carbon Tetrachloride-Induced Liver Cirrhosis

The hypothesis that dietary branched-chain amino acid (BCAA) supplementation improves the impaired protein turnover in male Donryu rats with carbon tetrachloride-induced liver cirrhosis was tested. We supplemented cirrhotic rats orally for 2 wk with BCAA solution [26.67 mg BCAA/(100 g body weight·d)], a conventional amino acid mixture [4.25 mg BCAA/(100 g body weight·d)] or saline and fed these three groups the AIN76 basal diet to have similar intakes of total energy and total nitrogen. Normal rats without liver cirrhosis were fed the basal diet similar to the above (noncirrhotic controls). After supplementation, rats were fed intravenous transthyretin (thyroxine-binding prealbumin) doubly labeled with 125I-tyramine-cellobiose and 131I. Kinetic indices including production rate of transthyretin were analyzed from plasma transthyretin disappearance curves. Tissue sites of transthyretin degradation were assayed using a trapped ligand technique by measuring 125I-tyramine-cellobiose levels. The production rate of transthyretin was significantly lower in cirrhotic rats supplemented with saline (mean 25.46 × 10-3·h-1) compared with noncirrhotic controls (45.08 × 10-3·h-1) (P < 0.05). This was corrected by supplementing cirrhotic rats with BCAA (37.05 × 10-3·h-1, P < 0.05) but not with conventional amino acid mixture (22.49 × 10-3·h-1). The accelerated degradation of transthyretin in muscles of cirrhotic rats was improved by BCAA (P < 0.05). In conclusion, dietary supplementation with BCAA improves the impaired transthyretin turnover in rats with liver cirrhosis.

Effect of endogenous hypergastrinemia on carcinogenesis in the rat esophagus.

We surgically prepared a hypergastrinemia model in rats and studied the effects of hypergastrinemia on chemically induced carcinogenesis in the esophagus. Operations were performed on 5-week-old male Donryu rats as follows: (1) truncal vagotomy plus pyloroplasty (group V), (2) segmental gastrectomy plus pyloroplasty (group G), (3) antrectomy (group A), and (4) no operation (group C) as a control. From the age of 6 weeks, the animals were given 0.003% N-methyl- N-amylnitrosamine (MAN) solution as drinking water for 8 weeks. After 20 weeks of MAN administration, the animals were bled and killed. The average serum gastrin levels in groups V and G were significantly higher than those groups C or A. There were significant differences between C and V in the incidence of carcinoma, and between V and A in the incidence of carcinoma including severe dysplasia. The incidence of histologically identified lesions per animal was determined, and significant differences were observed between C and both V and G in the incidence of carcinoma including severe dysplasia. Furthermore, we also detected gastrin receptors in the esophageal lesions produced by the oral administration of MAN to rats. The results of the present study suggest that endogenous hypergastrinemia has a positive influence on chemically induced carcinogenesis in the rat esophagus.

Effect of glutamine supplementation on protein metabolism and glutathione in tumor-bearing rats.

Since tumor-bearing rats are deficient in glutamine, we investigated whether (1) glutamine and glutathione deficiency occur in tumor-bearing rats, (2) glutamine supplementation caused an increase of glutathione levels in host tissues and tumor, (3) glutamine enhances protein synthesis in host tissues, and (4) glutamine stimulated the tumor to synthesize protein and DNA. Male Donryu rats were randomized into four groups: (1) non-tumor-bearing rat (NTB) + standard total parenteral nutrition (STPN); (2) NTB + glutamine-supplemented TPN (GTPN); (3) tumor-bearing rat (TB) + STPN; (4) TB + GTPN. On day 0 AH109A rat hepatoma cells were subcutaneously injected into the backs of rats to induce tumor. The animals were maintained on TPN for 6 days from day 10 through day 15. On day 15, 1-14C-leucine was given by a 5-hour continuous infusion (2.0 microCi/h per rat) to determine the fractional synthesis rate and endogenous leucine production. The levels of glutamine and glutathione were measured by HPLC. the tumor DNA synthesis was estimated by bromodeoxyuridine labeling index. Tumor development led to a significant weight loss, but this weight loss was significantly lessened by glutamine supplementation because of an increase in muscle protein synthesis. Glutamine did not enhance tumor weight, protein, and DNA synthesis in the tumor. Tumor development caused a significant reduction of glutathione in the muscle, jejunum, and liver, but supplemented glutamine increased the levels of glutathione in the jejunum. Glutamine supplementation is beneficial in preventing deficiencies of glutamine and glutathione and in improving protein metabolism in tumor-bearing rats.

Effect of methionine-deprived total parenteral nutrition on tumor protein turnover in rats.

Previous studies have shown that a methionine-lacking diet inhibited tumor growth in rats. The aim of this study was to determine how methionine free total parenteral nutrition (MTPN) can result in the inhibition of tumor growth on tumor protein metabolism in rats. On day 0, AH109A rat ascites hepatoma cells were implanted subcutaneously into male Donryu rats (n = 68, body weight, 200-225 gm). On day 10, a catheter for total parenteral nutrition (TPN) was placed and either MTPN or standard TPN solution was given for 5 days. On day 15, 1-14C-leucine was infused continuously to measure tumor protein synthesis. Tumor proteolysis was calculated from tumor regional blood flow, using the 85Sr-microsphere injection method. 1) Tumor weight was reduced with MTPN. 2) MTPN did not affect tumor protein synthesis, probably because endogenous methionine production was increased with MTPN (87.3 +/- 13.5 mumole methionine/kg/hour vs. 218.6 +/- 29.5, P < 0.01); however, MTPN caused an increase of tumor proteolysis (2.68 +/- 0.53 mumole leucine/g/hour vs. 3.79 +/- 0.73, P < 0.05). The enhanced tumor protein breakdown contributed to the inhibition of tumor growth that was found with the rats given the methionine free diet.

Effect of Glutamine Supplement and Hepatectomy on DNA and Protein Synthesis in the Remnant Liver

One of the physiological roles of glutamine is as a precursor for DNA synthesis. The aims of this study were to determine (1) whether glutamine-supplemented total parenteral nutrition (TPN) enhanced DNA and protein synthesis in the liver and (2) whether glutamine uptake was increased following partial hepatectomy in rats. Male Donryu rats ( n = 59; body weight, 250-275 g) were randomized into four groups: (1) sham operation + standard TPN solution (C-STPN); (2) C + glutamine-supplemented TPN (C-GTPN); (3) 70% partial hepatectomy + STPN (H-STPN); (4) partial hepatectomy + GTPN (H-GTPN). On Day 0, rats underwent either a sham operation or 70% partial hepatectomy and concomitantly were catheterized in the jugular vein. TPN was begun immediately after the surgery. GTPN was isocaloric and isonitrogenous with STPN and 25% of total nitrogen was given as glutamine. On Day 2, the animals were sacrificed after either a continuous infusion of 1- 14C-leucine or a bolus iv injection of bromodeoxyuridine. The rate of hepatic regeneration was enhanced with glutamine supplementation (H-STPN, 60.8 ± 1.6% vs H-GTPN, 66.3 ± 2.0, P < 0.05) due to an increase in protein synthesis in the liver (H-STPN, 134.0 ± 10.3%/day vs H-GTPN, 160.9 ± 6.9, P < 0.05) and DNA synthesis in hepatocytes (H-STPN, 23.1 ± 2.5% vs H-GTPN, 31.4 ± 2.9, P < 0.05). The uptake of glutamine by the liver was increased following hepatectomy with GTPN supplementation. In conclusion, glutamine supplement and partial hepatectomy stimulated glutamine uptake in the liver and this results in an enhancement of protein and DNA synthesis in the remnant liver.

Regulation of albumin synthesis after hepatectomy and in the acute inflammation phase of rat liver

Hepatic albumin synthesis is down-regulated after both inflammation and hepatectomy. The transcriptional control of albumin synthesis was investigated in models of both conditions to differentiate the underlying mechanisms. Male Donryu rats underwent 70% hepatectomy or turpentine injection. Serum albumin and mRNA levels of albumin and promoter binding proteins (D site binding protein [DBP] CCAAT/enhancer binding protein-α[ C EBP -α], -β , and hepatocyte nuclear factor-1 [HNF-1]) in the liver were measured from 0 to 96 hr. After hepatectomy, the albumin mRNA level decreased to 0.6 at 36 hr and then recovered. After turpentine injection, it decreased to 0.4 at 36 hr and then recovered. The serum level of albumin decreased in a time-dependent manner in both models. The C EBP -α mRNA level decreased to 0.5 at 6 and 12 hr after hepatectomy and to 0.6 at 24 hr after turpentine injection. The DBP mRNA level decreased to 0.3 at 6 hr, to 0.2 at 24 hr after hepatectomy, and to 0.3 at 30 hr after turpentine injection. The C EBP -β mRNA level increased to 1.7 at 3 hr after hepatectomy and to 1.5 at 12 hr after turpentine injection. On the other hand, HNF-1 mRNA levels showed no consistent change in either model. The change in mRNA of the nuclear factors ( C EBP -α, C EBP -β , and DBP) thus precedes that of albumin. In conclusion, transcriptional regulation of albumin synthesis in the regenerating and the acute inflammation phase of the liver can be assessed by monitoring the mRNA levels of nuclear factors. The mechanisms for down-regulation of albumin in both conditions share substantial similarities.

Effects of branched-chain amino acid infusion on protein metabolism in rats with acute hepatic failure

Branched-chain amino acids (BCAA) are known to improve hepatic encephalopathy as well as protein malnutrition in cirrhosis. However, such effects in acute hepatic failure (AHF) remain to be elucidated. The current study was conducted to investigate whether BCAA improves protein metabolism in AHF. AHF was induced in male Donryu rats weighing approximately 230 g by giving 60 mg/kg lipopolysaccaride intravenously and 800 mg/kg D-galactosamine hydrochloride intraperitoneally. From 18 hours after injection, AHF rats and control rats were given one of the following five solutions intravenously for 6 hours: 1) saline, 2) 10% glucose, 3) standard 10% amino acid formula with total nitrogen content of 12.2 g/L and BCAA/aromatic amino acid molar ratio of 37.05, 4) BCAA-enriched solution with nitrogen content of 21.9 g/L and the ratio of 148.2, or 5) an active placebo against BCAA-enriched solution with nitrogen content of 21.9 g/L and the ratio of 37.05. In parallel, each group was given a continuous infusion of 14C-leucine. After the plasma radioactivity of 14C-leucine and the expired 14CO 2 level reached a plateau, protein turnover was analyzed according to the kinetic model proposed previously by Waterlow. When compared with the control, rates of total protein turnover (total flux), oxidation, and breakdown all increased significantly in AHF. Infusion of standard 10% amino acid formula, BCAA-enriched solution or the placebo in AHF increased total flux and oxidation significantly as compared with the effect of saline or 10% glucose. Although saline, 10% glucose, standard 10% amino acid formula, and the placebo had no effect on synthesis rate, it was increased significantly with BCAA-enriched solution. Breakdown was not suppressed with any solution. These results suggest that rats with AHF are in a catabolic state and that any of the three amino acid solutions can be oxidized to provide energy in AHF. In addition, infusion of BCAA-enriched solution may have a specific protein-sparing effect by increasing the protein synthesis rate even with liver damage. Hence, it is conceivable that infusion of BCAA improves protein metabolism in AHF.

Effects of branched-chain amino acid infusion on protein metabolism in rats with acute hepatic failure

Branched-chain amino acids (BCAA) are known to improve hepatic encephalopathy as well as protein malnutrition in cirrhosis. However, such effects in acute hepatic failure (AHF) remain to be elucidated. The current study was conducted to investigate whether BCAA improves protein metabolism in AHF. AHF was induced in male Donryu rats weighing approximately 230 g by giving 60 mg/kg lipopolysaccaride intravenously and 800 mg/kg D-galactosamine hydrochloride intraperitoneally. From 18 hours after injection, AHF rats and control rats were given one of the following five solutions intravenously for 6 hours: 1) saline, 2) 10% glucose, 3) standard 10% amino acid formula with total nitrogen content of 12.2 g/L and BCAA/aromatic amino acid molar ratio of 37.05, 4) BCAA-enriched solution with nitrogen content of 21.9 g/L and the ratio of 148.2, or 5) an active placebo against BCAA-enriched solution with nitrogen content of 21.9 g/L and the ratio of 37.05. In parallel, each group was given a continuous infusion of 14C-leucine. After the plasma radioactivity of 14C-leucine and the expired 14CO2 level reached a plateau, protein turnover was analyzed according to the kinetic model proposed previously by Waterlow. When compared with the control, rates of total protein turnover (total flux), oxidation, and breakdown all increased significantly in AHF. Infusion of standard 10% amino acid formula, BCAA-enriched solution or the placebo in AHF increased total flux and oxidation significantly as compared with the effect of saline or 10% glucose. Although saline, 10% glucose, standard 10% amino acid formula, and the placebo had no effect on synthesis rate, it was increased significantly with BCAA-enriched solution.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of gomisin A on the promotor action and serum bile acid concentration in hepatocarcinogenesis induced by 3'-methyl-4-dimethylamino-azobenzene.

The effects of gomisin A, a lignan component of Schizandra fruits, on the promotion stage of hepatocarcinogenesis initiated by 3'-methyl-4-dimethylamino-azobenzene (3'-MeDAB) in male Donryu rats were investigated. When different types of tumor promotors, phenobarbital (PB) and deoxycholic acid (DCA), were administered for 5 weeks after initiation by 3'-MeDAB, preneoplastic alterations in the liver, determined by glutathione S-transferase placental form (GST-P), were markedly increased. Gomisin A significantly inhibited the increase in number and size of GST-P positive foci, regardless of the promotor. This lignan inhibited the increase in serum bile acid concentration by administration of DCA, but hardly influenced the serum bile acids in the PB-combined group. These results suggest that the inhibitory effect of gomisin A on the promotive action of DCA is based on improving bile acid metabolism, but regarding the action of PB, the effect could not be elucidated from the metabolism of bile acids.

Endotoxemia and Intestinal Mucosal Dysfunction after the Relief of Obstructive Jaundice by Internal and External Drainage in Rats

We studied the effects of external and internal biliary drainage on the development of endotoxemia in a rat model of obstructive jaundice. Male Donryu rats were allocated to four groups: sham operation, common hepatic bile duct ligation (BDL), internal or external biliary drainage after BDL, and biliary drainage after BDL with oral endotoxin administration. Portal and systemic blood endotoxin concentrations were measured and the histomorphology of the intestinal mucosa was examined. Portal endotoxemia was observed 7 days after BDL and both portal and systemic endotoxemia were observed after 14 days. Portal endotoxemia was reversed by both internal and external biliary drainage and systemic endotoxemia was prevented. The ratio of villous height to crypt depth in the mucosa of the terminal ileum was decreased in rats with external drainage. Oral administration of endotoxin induced marked disruption of the mucosal epithelium in rats with external biliary drainage, but not in rats with internal biliary drainage. Significant increases in portal and systemic blood endotoxin concentrations were observed only in the external drainage group after oral endotoxin administration. The relief of biliary obstruction effectively relieved portal endotoxemia. External biliary drainage, however, has the potentially deleterious effect of disrupting the intestinal mucosa, which may promote the development of endotoxemia. These findings have implications for the use of biliary drainage procedures to reduce postoperative complications in jaundiced patients.

Carcinogen daily dose-dependence of the biological features and development rate of hepatocellular carcinomas induced by 3'-methyl-4-dimethylaminoazobenzene in the rat.

Differences in biological features and the rate development of hepatocellular carcinomas (HCCs) induced with various daily doses of 3'-methyl-4-dimethylaminoazobenzene were investigated. Male Donryu rats at 21 days old were fed the carcinogen at concentrations ranging from 50 to 600 ppm in the diet continuously, or 600 ppm for 3 weeks followed by a dietary promoting regimen of 500 ppm phenobarbital. Large (> or = 10 mm) HCCs were monitored and the histological features and alpha-fetoprotein (AFP) production analysed. High doses of the carcinogen predominantly induced HCCs of high grade malignancy with AFP production in a short latent period whereas lower doses and the initiation-promotion protocol were primarily associated with low grade HCCs lacking AFP production and developing after long latent periods. Thus the experimental results clearly document that biological features of neoplasms, viewed as a spectrum, may markedly differ according to the daily dose of the carcinogen applied.

Effect of Glutamine and Chemotherapy on Protein Metabolism in Tumor-Bearing Rats

Supplemental glutamine prevents gut atrophy and enhances muscle protein synthesis in septic rats. This study investigated the effect of glutamine administration and mitomycin C treatment on protein turnover in tumor-bearing rats. AH109A rat ascites hepatoma cells (2 × 106) were subcutaneously implanted in the back of male Donryu rats (n = 32, body weight 150-200 g) on Day 0. The animals were then fed rat chow ad libitum for 10 days. On Day 10, the rats were catheterized for TPN and randomized into four groups according to diet and treatment. The groups were: (i) standard total parenteral nutrition (STPN) + saline; (ii) glutamine-supplemented TPN (GTPN) + saline; (iii) STPN + mitomycin C (MMC); (iv) GTPN + MMC. GTPN was isocaloric (250 kcal/kg/day) and isonitrogenous (1.5 gN/kg/day) with STPN. The animals were maintained on TPN for 5 days and received mitomycin C (0.5 mg/kg) via the catheter every day. On the fifth day of TPN, [1-14C]leucine was given via a 5-hr continuous infusion (2.0 μCi/hr/rat) to determine the fractional synthesis rate of muscle, gut mucosa, liver, and tumor. Also, endogenous leucine production (≑whole body protein breakdown rate) was calculated. Body weight loss during TPN was reduced with GTPN. GTPN enhanced muscle FSR in untreated animals (STPN: 10.8 ± 8.7%/day vs GTPN: 14.7 ± 0.6%/day, P < 0.05) and in mitomycin C-treated animals (STPN + MMC: 9.6 ± 0.9%/day, GTPN + MMC: 12.0 ± 0.8%/day, P < 0.05). The whole body protein breakdown rate was reduced with GTPN. Mitomycin C reduced the mucosal fractional synthesis rate and GTPN did not prevent this reduction. There was no effect of glutamine on tumor protein synthesis. These results showed that glutamine supplementation improved nitrogen retention in tumor-bearing rats during chemotherapy without enhancing tumor growth.

Effects of intravenous infusion of dopamine on tumor blood flow in rat subcutis.

To determine the effects of intravenous administration of dopamine hydrochloride (DA) on tumor blood flow (TBF), we measured the blood flow of normal subcutaneous tissue and subcutaneous tumor (LY‐80, a variant of Yoshida sarcoma) in enflurane‐anesthetized male Donryu rats using a hydrogen clearance method. Measurements were made before and during intravenous infusion of DA at a rate of 5μg/kg/min, while recording the mean arterial blood pressure of the rats. Under mild hypertension induced by DA, the blood flow of normal subcutis decreased and TBF increased significantly. SCH‐23390, an antagonist of the DA1 receptor, inhibited the enhancement of TBF by DA; while domperidone, an antagonist of the DA2 receptor, did not modify the effects of DA. In experimental chemotherapy against the tumor using adriamycin (ADM) 5 mg/kg i.v., only the combination of DA and ADM significantly inhibited the tumor growth. Moreover, DA reduced the weight loss caused by ADM. These results indicate that DA could have a role in increasing TBF and possibly enhance drug delivery to tumors. Moreover, it appears that the DA1 receptor contributes, at least in part, to the enhanced blood flow in rat subcutaneous tumor following DA administration.

Parvalbumin expression in the diaphragm of aged rats

Parvalbumin is a calcium-binding protein involved in the mechanism of Ca(++) exchange between the sarcoplasmic reticulum and the myofibrils. There is a direct correlation between the amount of parvalbumin and the velocity of contraction-relaxation of skeletal muscle fibers. Male Donryu rats (6, 24 and 30 months of age) were housed in a specific pathogen free room and fed with 60% of the mean daily quantity of rodent chow consumed by rats fed ad libitum. To assess the expression of parvalbumin in the rat diaphragm, transversal sections were processed immunohistochemically using polyclonal antiparvalbumin antibody. The stained sections were inspected on an image analysis device to evaluate the intensity of the immunoreaction and to take morphological measurements of the muscle fibers. The optical density data allowed the distinction of fibers in fast- and slow-twitch types. The results show that the number of fibers did not change in young and old rats, but the percentage of muscle fibers containing parvalbumin decreased with age. Moreover, the fast-twitch fibers showed a remarkable decrease in their diameter at 30 months of age, but the slow-twitch ones did not. The results suggest that, as the organism gets old, the fiber type composition of the diaphragm changes to adapt to different physiological and/or metabolic exigencies.