Choleretic effects of ursodeoxycholic acid on experimentally-induced intrahepatic cholestasis

When a lymphokine, the cholestatic factor, is intravenously injected into rats through a mesenteric vein, remarkable reductions in bile flow and bile acid excretion are observed. Using this experimentally-induced intrahepatic cholestasis model, the choleretic effects of ursodeoxycholic acid (UDCA) were studied. When UDCA was injected with the cholestatic factor, the reductions in bile flow and bile acid excretion were significantly suppressed. Remarkable choleretic effects were also noted, when UDCA was administered to normal rats. These results suggested that UDCA may be effective in the treatment of intrahepatic cholestasis.     

Bile acid metabolism in ascorbic acid-deficient guinea pigs.

Sterol balance techniques have been used to determine the effect of short-term ascorbic acid (AA) deprivation on bile acid excretion in the guinea pig. The effects of a brief (2-week) AA deficiency on bile acid pool sizes and the activity of the rate controlling enzyme in bile acid biosynthesis have been determined. It was found that, while food intake and body weight were not affected by the short-term AA deficiency, liver AA levels had fallen to 25% of control levels. At the same time, the rate of excretion of bile acids and the size of the bile acid pool were both reduced by about 50% in guinea pigs deficient in AA. These results were supported by a decrease in the activity of cholesterol 7 alpha-hydroxylase in the deficient animals. It is concluded that an AA deficiency will significantly impair bile acid metabolism independent of any side effects of clinical scurvy.     

Effect of taurine on total parenteral nutrition-associated cholestasis

A decrease in the formation/secretion of bile has been well documented in animals on total parenteral nutrition (TPN). Either an excess or an imbalance of amino acids (AA) has been most often implicated. In view of recent work showing that taurine promotes bile flow, bile acid secretion, and protects against hepatotoxic bile acids, the effect of adding taurine (15 mg/dL) to an AA solution was examined in guinea pigs on TPN for 3 days. The TPN-taurine group had a larger bile flow than the group without taurine and had bile acid secretory rates (BASR) similar to those of controls who were on saline by central catheter and had free access to food. Bile composition showed an increase in the secondary bile acid, 7-ketolithocholate and a concomitant decrease in chenodeoxycholate (CDC) in both experimental groups. Taurine led to a reversal of the usual predominance of glycine over taurine conjugated bile acids as well as to increases in HCO3 in cholesterol secretion. In response to a challenge with a large load of CDC, the TPN-taurine animals increased their BASR beyond those observed in the two other groups. These observations suggest that the addition of taurine to TPN solutions could play a role in the prevention of altered biliary function associated with AA solutions.     

腺苷蛋氨酸预防大鼠全肠外营养并发的胆汁淤积

目的：观察Ｓ－腺苷－Ｌ－蛋氨酸（ＳＡＭｅ）对大鼠ＴＰＮ胆汁淤积的预防效果,并比较胆汁中胆盐的变化。方法：１８只ＳＤ大鼠随机分为三组,对照组,ＴＰＮ组,ＴＰＮ＋ＳＡＭｅ组,每组各６只,后两组均ＴＰＮ支持５天,然后插管收集胆汁,测量胆汁流量,采血检测血清总胆酸（ＳＴＢＡ）、ＧＧＴ、ＡＬＴ,ＡＫＰ水平,观察光镜,电镜下肝的病理变化,检测胆汁中胆盐含量。结果：ＴＰＮ组出现胆汁流下降,ＳＴＢＡ,ＧＧＴ水平升     

Long-term effects of inadequate and excessive dietary ascorbate on bile acid metabolism in the guinea pig

The effects of long-term chronic ascorbic acid deficiency and excessive ascorbic acid consumption on bile acid metabolism and biliary lipid composition were studied in guinea pigs. Male, weanling guinea pigs were fed a cereal-based scorbutigenic diet for 19 or 21 weeks. Ascorbic acid was administered either orally at 0.15 (group A) or 2.0 (group B) mg/100 g body weight, or it was mixed in the diet at levels of 500 (group C), 16-22 (group D), or 20,000 mg/kg (group E). Chronic ascorbic acid deficiency (groups A and D) caused depression of hepatic cytochrome P-450 levels and elevation of plasma cholesterol. Excessive ascorbate consumption did not alter these parameters relative to control levels. In contrast to results obtained in guinea pigs fed low or high amounts of ascorbate for 7-9 weeks, prolonged consumption of inadequate or excessive ascorbate resulted in little or no change in bile acid metabolism and biliary lipid composition except that bile acid pool size was increased 12% as a result of excessive ascorbate ingestion. Results of the present study suggest that there may be important differences in the guinea pig's metabolic response to ascorbic acid deficiency and ascorbic acid excess, depending on the length of the experimental period.     

Low protein diets potentiate lithocholic acid-induced cholestasis in rats.

Earlier studies showed that low protein diets (LPD) reduce bile flow and bile acid secretion. We therefore examined the effect of LPD on lithocholic acid (LCA)-induced intrahepatic cholestasis. Female Sprague-Dawley rats were fed LPD (8% casein) soon after weaning for 4 or 12 wk, and then were injected intravenously with a single dose of LCA (4 mumol/100 g body wt). Bile was collected for 30-min periods, and bile flow as well as biliary lipid secretory rates were measured. Bile acid metabolism was also studied and the results were compared with those obtained in rats fed an adequate protein diet (26% casein). The LPD produced significantly lower bile flow and bile acid secretion, which were attributed to a reduced bile acid pool and a reduction in synthesis. They also enhanced the LCA-induced decline in bile flow, and rate of biliary output of total bile acids, phospholipids and cholesterol. The LPD were also associated with impaired LCA secretion in bile and increased retention in plasma and liver. Studies of LCA metabolism in rats fed a LPD indicated lower hepatic LCA hydroxylation, a greater percent contribution of glyco conjugates and lower levels of tauro conjugates. The present findings suggest that the reduced bile acid pool size, diminished LCA excretion and biotransformation to less toxic bile acids may explain the greater cholestasis in LPD-fed rats.     

Corn fiber oil lowers plasma cholesterol by altering hepatic cholesterol metabolism and up-regulating LDL receptors in guinea pigs

To evaluate some of the mechanisms involved in the hypocholesterolemic effects of corn fiber oil (CFO), male Hartley guinea pigs were fed diets containing increasing doses of CFO [0 (control), 5, 10 or 15 g/100 g]. Total fat was adjusted to 15 g/100 g in all diets with regular corn oil. Diets contained 0.25 g/100 g cholesterol. A positive control group (LC) with low dietary cholesterol (0.04 g/100 g) was also included. Plasma LDL cholesterol concentrations were 32, 55 and 57% (P < 0.0005) lower with increasing doses of CFO. Compared with controls, intake of CFO resulted in 27-32% lower hepatic microsomal cholesterol (P < 0.0001), the regulatory pool of LDL receptor (LDL-R) expression. CFO intake resulted in favorable plasma and hepatic cholesterol concentrations, similar to those in guinea pigs fed the LC diet. Hepatic cholesterol 7alpha-hydroxylase (CYP7) activity was approximately 88% higher in guinea pigs fed the two higher dosages of CFO (P < 0.05). In parallel, CYP7 mRNA abundance was approximately 88% higher in guinea pigs fed all three CFO diets. CFO treatment also induced hepatic LDLR mRNA by 66-150% with significant differences at the highest CFO dose. These results suggest that CFO, as a result of decreased bile acid absorption, increased mRNA abundance and activity of CYP7. Because hepatic cholesterol is the substrate for CYP7, a lowering of cholesterol concentrations in the total and microsomal pools was observed. As a response to the depleted microsomal free cholesterol pool, the LDL receptor was up-regulated, drawing more cholesterol from plasma, thus leading to the observed decrease in plasma LDL cholesterol concentrations.     

腺苷甲硫氨酸对感染大鼠全肠外营养胆汁淤积的预防

目的：观察S－腺苷－L－甲硫氨酸（S－Adenothyl-L-methionine,SAMet)对感染大鼠TPN淤胆的预防效果。方法：18只体重240－280g的SD雄性大鼠随机分为三组；对照组，感染＋TP组，感染＋TPN＋SAMet组，每组各6只，后两组均结扎盲肠致感染并持续TPN支持5天。SAMet按80mg/(kg.d)加入营养液中。实验结束，胆总管插管收集胆汁，测流量，采用检测血清总胆酸（STBA）、GGT、ATLT、AKP水平，光镜、电镜下观察肝病理变化，HPLC法检测胆汁中八种结合胆直总胆盐含量。结果：感染＋TPN组与对照组比较出现胆汗流下降，STBA、GGT、AKP水平升高，病理检查见肝组织脂肪浸润、毛细胆管扩张及胆栓；而感染＋TPN＋SAMet组较感染＋TPN组胆汁流升高，STBA、GGT、ALT、AKP水平均显著下降，肝 正常或病理改变明显减轻。胆汁胆直部仅个别胆盐有差异，其余绝大部分胆盐间无显著差异。结论：在感染大鼠实施TPN时给予SAMet可有效预防TPN胆汁淤积的发生，为临床上有不停止TPN的情况下预防淤胆的发生提供了一种新的措施。     

Effect of folate deficiency on microsomal drug metabolism and heme content in the intestinal mucosa of guinea pigs

The relationship between folate deficiency, heme content, and microsomal drug metabolism in the intestinal mucosa of the guinea pig was examined. Weanling male guinea pigs were pair‐fed a folate‐deficient diet, and intestinal mucosal folate levels were measured. A significant decrease (75%) in these levels was observed at 3 weeks after diet initiation. A significant decrease (78%) in intestinal mucosal drug metabolism (7‐ethoxycoumarin O‐deethylase activity) and a significant decrease (46%) in intestinal mucosal heme content were also observed at this time. These findings indicate that folic acid deficiency in the guinea pig results in a marked reduction in heme content and microsomal drug metabolism of the intestinal mucosa.     

Isolated perfused liver model: the rat and guinea pig compared

OBJECTIVE: Although the rat is the most commonly used species for the study of hepatic metabolism, the physiology of the guinea pig is closer to human physiology. We compared the model of isolated perfused guinea pig liver with the classic model of isolated perfused rat liver, especially with respect to amino acid metabolism. METHODS: After validation of an anesthetic mixture of ketamine, diazepam, and xylazine for the guinea pig, isolated perfused livers were harvested for both species. Three groups of animals were compared for the study of liver metabolic fluxes: 6-wk-old male Sprague-Dawley rats (R; 230 +/- 10 g, n = 5), young male Hartley guinea pigs (YG; 223 +/- 8 g, n = 6) matched to rats by liver weight, and adult male Hartley guinea pigs (AG; 389 +/- 5 g, n = 6) matched to rats by age. Results (mean +/- standard error of the mean) were compared by analysis of variance and Newman-Keuls tests. RESULTS: Both models displayed a satisfactory hepatic viability, but differences were noted, with higher portal flows (R: 3.1 +/- 0.3 versus YG: 4.5 +/- 0.3 and AG: 4.2 +/- 0.3 mL. min(-1). g(-1); P < 0.05, YG and AG versus R) and bile flows (R: 0.34 +/- 0.01 versus YG: 2.38 +/- 0.22 versus AG: 3.17 +/- 0.28 microL. min(-1). g(-1); P < 0.05, YG and AG versus R, and YG versus AG) and higher amino acid fluxes (P < 0.05) leading to greater nitrogen uptake (P < 0.05) in guinea pigs. We performed a second set of experiments to evaluate the influence of anesthesia and portal flow on this last parameter. In these experiments, rats were anesthetized with ketamine, diazepam, and xylazine and guinea pig livers were perfused at rat blood flow. Apart from a 50% anesthesia-related mortality for rats, bile flow and metabolic parameters were only slightly modified. However, some amino acid fluxes were statistically different (aspartate, serine, and histidine; P < 0.05), as confirmed by a higher transfer constant. CONCLUSION: Our results indicate that the isolated perfused guinea pig liver is a suitable model for the study of hepatic metabolism.     

The disaccharide effect of sucrose feeding on glucuronide excretion and bile concentration of injected phenolphthalein in guinea pigs

The hypothesis tested was that feeding guinea pigs sucrose produces a more rapid concentration in the bile and excretion in the feces and urine of substances catabolized by the liver than does feeding invert sugar (50:50 mixture of glucose and fructose). Fifty male guinea pigs of the Hartley strain were divided into two groups of 25 animals each and fed for 4 wk repelleted nonpurified diet with 20% of total energy provided by sucrose or invert sugar. At the end of 4 wk all 50 animals were injected i.p. with a dose of 15 mg/kg body weight of phenolphthalein. Phenolphthalein is excreted almost quantitatively in feces. After injection all guinea pigs were housed in metabolism cages. Urine and feces were recovered and analyzed for free glucuronic acid and glucuronide content by a modified naphthoresorcinol procedure over 24 h. Guinea pigs fed sucrose produced more urine than those fed invert sugar, although there was no difference in water intake. After 24 h 15 animals in each group were killed, and the bile was sampled from their gall bladders to determine its phenolphthalein content. The remaining 10 animals in each group were held three additional days when they were killed and their bile was sampled to determine its phenolphthalein content. All biliary phenolphthalein was in conjugated form. Guinea pigs fed sucrose had less free glucuronic acid in their feces than those fed invert sugar. Feeding sucrose resulted in a higher bile conjugated phenolphthalein content 4 d after injection than did feeding invert sugar.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dietary raw peas (Pisum sativum L.) reduce plasma total and LDL cholesterol and hepatic esterified cholesterol in intact and ileorectal anastomosed pigs fed cholesterol-rich diets

Previous studies demonstrated the cholesterol-lowering effect of dietary legumes (mainly soybeans) in animals and humans, but the mechanisms by which they exert this effect are not completely understood. The contribution of the hindgut to this hypocholesterolemic effect is also not well documented. The present work was undertaken to investigate the effect of cholesterol-enriched (2.8 g/kg) casein (C) and raw pea seed (RP) diets on the cholesterol metabolism of intact (I) and ileorectal anastomosed (IRA) growing pigs. Four groups of 6 pigs were allocated to the treatments (C-I, C-IRA, RP-I, and RP-IRA pigs) for 3 wk. Plasma total cholesterol was lowered by the RP diet through a significant decrease in LDL cholesterol. The RP diet also decreased the hepatic concentration of esterified cholesterol and increased 3-hydroxy-3-methylglutaryl CoA reductase activity and LDL receptor synthesis. The biliary total cholesterol and bile acid concentrations were greater in RP- than in C-fed pigs. In addition, fecal bile acid output was higher in RP-fed pigs. The cecum-colon by-pass inhibited cholesterol and beta-sitosterol microbial transformation, lowered the bile acid output, and increased the primary to secondary bile acid output ratio, but its influence on cholesterolemia was negligible. These results suggest a hypocholesterolemic effect of the raw pea diet probably due to increased fecal bile acid output and an increased biliary bile acid concentration.     

Effect of erythorbic acid administration on activities of drug metabolic enzyme and phosphatases in guinea pigs administered an adequate amount of ascorbic acid

The effect of erythorbic acid (ErA) administration on activities of liver aniline hydroxylase, liver acid phosphatase, and serum alkaline phosphatase, and the content of liver cytochrome P-450 was studied to determine whether or not ErA would affect the availability of ascorbic acid (AsA) in normal and AsA-deficient guinea pigs. In experiment I, changes of the enzyme activities and liver cytochrome P-450 content in the guinea pigs administered AsA and/or ErA and sacrificed on days 4, 10, 16, and 30 were examined. Moreover, in experiment II, after 16 days of depletion of AsA, the guinea pigs were administered AsA and/or ErA. These animals were sacrificed on days 0, 4, and 20 of the repletion period, after which the activities of drug metabolic enzyme and phosphatases and content of cytochrome P-450 during recovery were observed. The enzyme activities and cytochrome P-450 content of AsA-supplemented guinea pigs were similar to those of ErA-supplemented animals and also similar to those of both AsA and ErA-supplemented guinea pigs throughout the experimental period. During the repletion of the AsA-depleted guinea pigs, there were no significant differences in these enzyme activities and cytochrome P-450 content among the animals administered AsA and/or ErA. These results suggested that ErA administration may not affect the AsA availability in the guinea pigs.     

ASCORBIC ACID AND THE CATABOLISM OF CHOLESTEROL

Guinea pigs with a latent, chronic ascorbic acid deficiency were injected with 26-¹⁴C-cholesterol and the conversion of the labeled chofesterol into bile acids was estimated by following the output of ¹⁴CO₂ for several weeks. Deficient guinea pigs accumulated serum and tissue cholesterol and had a lower output of ¹⁴CO₂ than did the controls. In addition, the turnover time of the labeled cholesterol was less than that of contols. From these, as well as previous results, it was concluded that adequate tissue concentrations of ascorbic acid were necessary for conversion of cholesterol to bile acids.     

Reduction of dehydroerythorbic acid in vitamin C-deficient guinea pigs.

A reduction of dehydroerythorbic acid (DERA) to erythorbic acid (ERA) in vitamin C-deficient guinea pigs was evaluated and compared with that of dehydroascorbic acid (DASA). Thirty-six guinea pigs were fed with vitamin C-deficient diets for 18 days. On day 19, the guinea pigs were divided into four groups for the administration of 100 mg of DERA, ERA, ascorbic acid (ASA), or DASA every day. After 12 days of oral administration, the concentration of DERA, ERA, ASA, and DASA in the liver, adrenal, spleen, kidney, and plasma of guinea pigs was determined by HPLC. A recovery from scurvy was measured in terms of weight gain and serum alkaline phosphatase activity. All four groups showed similar recovery, indicating that the oral administration of relatively high concentrations of DERA reversed the effects of scurvy in vitamin C-deficient guinea pigs. In spite of DERA or DASA administration, ERA or ASA was mainly detected in the tissues. The reduction ratios of DEAR and DASA were similar (approximately 80%) in all tissues except spleen. These results suggest that both DASA and DERA are taken up and reduced to ASA or ERA in vivo.     

Levels of minerals in serum and urine of guinea pigs following intraperitoneal administration of ascorbate

The effect of ascorbic acid administration on the levels of urinary and serum mineral nutrients, Ca, Cu, Fe, K, Mg, Mn, Na and Zn in guinea pigs has been studied. Male guinea pigs received sodium ascorbate solution (equivalent to 1 g ascorbic acid/kg body weight/day) by intraperitoneal injection for 4 weeks. During the ascorbic acid treatment period, serum and urinary ascorbic acid rose markedly. The large quantities of ascorbic acid intake did not influence serum levels of all eight minerals studied when experimental values were compared with controls using the two-tailed Student's t-test. However, when the one-tailed t-test was used, serum copper and zinc levels of the experimental guinea pigs were significantly lower than their respective control values. Excepting sodium, derived from injected sodium ascorbate, no differences in daily urinary excretion of the other seven minerals were observed.     

The tissue distribution of L-ascorbic acid and dehydro-L-ascorbic acid in the guinea pigs injected intravenously with dehydro-L-ascorbic acid

The tissue distribution of L-ascorbic acid (AsA) and dehydro-L-ascorbic acid (DAsA) in guinea pigs injected with DAsA intravenously was examined using high-performance liquid chromatography. DAsA injected into guinea pigs fed normal diets containing AsA (control group) was readily taken into erythrocytes, and AsA contents of plasma and other tissues rapidly increased after DAsA injection. In animals fed vitamin C-deficient diets, DAsA was also detected in erythrocytes; however, the increase of AsA in their tissues was considerably less than that of control group. From these results, it was suggested that utilization of DAsA as AsA in vitamin C-deficient guinea pigs was less than that of control animals, and the reduction mechanism of DAsA to AsA in vitamin C-deficient guinea pigs may have differed from that of control groups.     

Respiratory response of guinea pigs to low levels of sulfuric acid

Sulfuric acid at concentrations of 0.1 to 1 mg/m³ produces an increase in pulmonary flow resistance and a decrease in pulmonary compliance in guinea pigs exposed for 1 hour. These changes are not rapidly reversible following termination of exposure. Sulfuric acid of 0.3 μm (MMD) was more irritant than a larger size of 1 μm.     

The influence of 2,2',4,4',5,5'-hexachlorobiphenyl on the placental blood flow in guinea pigs at a late stage of gestation

Three groups of primaparous pregnant guinea pigs were fed once daily with a total of either 0 (control group, n = 9), 3 (n = 8), or 30 mg (n = 9) of 2,2',4,4',5,5'-hexachlorobiphenyl (HCB) starting at Day 45 of gestation to evaluate the effects of HCB on placental perfusion. The guinea pigs were separated into their groups randomly. At Day 63 of gestation the organ blood flow was determined with microsphere technique in the awake animal. The results show a statistically significant decrease in the placental blood flow and an increase in the pulmonary blood flow in the animals fed with 30 mg HCB compared to the control groups. A higher incidence of resorptions in fetuses is shown in both treatment groups compared to the control group. It is concluded that ecologically relevant doses of polychlorinated biphenyls might cause a deterioration in the placental function by reducing its blood flow.     

Role of ascorbic acid on tyrosine hydroxylase activity in the adrenal gland of guinea pig.

The decrease of tyrosine hydroxylase activity in adrenal homogenate in scurvy was recovered after the administration of ascorbic acid. The causes of the increase in the enzyme activity after the administration of ascorbic acid have been studied. 1. No significant elevation in the enzyme activity was observed after the administration of reserpine to the scortutic guinea pig. 2. A dose of metal chelating agent, alpha, alpha'-dipyridyl, prevented the ascorbic acid-induced or reserpine-induced increase in enzyme activity in the scorbutic and the non-scorbutic guinea pigs, respectively. 3. Tyrosine hydroxylase activity was partially recovered by the administration of FeSO4 to the scorbutic guinea pig. From these results, it became clear that the induction of tyrosine hydroxylase which was not observed in scurvy was due to the deficiency of Fe2+. These results suggested that ascorbic acid affected the induction of this enzyme via Fe2+.