Biliary excretion of [14C]taurocholate by rainbow trout (Salmo gairdneri) is stimulated at warmer acclimation temperature

Sexually immature Shasta strain rainbow trout (Salmo gairdneri) of either sex were acclimated at 10, 14 or 18 degrees C for at least 4 weeks and plasma pharmacokinetics and biliary excretion of i.p. injected [14C]taurocholate (TC) examined in spinally transected or free-swimming fish, respectively. Plasma elimination half-lives but not absorption rate constants for [14C]TC (10 mumol/kg) were about two-fold reduced in 18 as compared to 10 or 14 degrees C acclimated fish. Distribution of [14C]TC to tissues other than plasma, liver, bile and small intestine was not different in 10, 14 or 18 degrees C acclimated free-swimming fish at 1 or 4 hr post-injection. Biliary excretion of [14C]TC (7.5-10 mumol/kg) at 1 hr post-injection was significantly higher in 14 and 18 as compared to 10 degrees C acclimated fish.     

Dynamics of the conjugate pattern during the infusion of bile acids into isolated rat liver

The conjugate pattern of biliary [14C]bile acids was investigated in isolated perfused rat livers, which were infused with either [24-14C]cholic acid or [24-14C]chenodeoxycholic acid (40 mumol/h) together with or without taurine or cysteine (80 mumol/h). [14C]Bile acids were chromatographed on a thin-layer plate and the distribution of radioactivity on the plate was measured by radioscanning. The biliary excretion of [14C]bile acids was greater in the infusion with [14C]cholic acid than in the infusion with [14C]chenodeoxycholic acid. Biliary unconjugated [14C]bile acids amounted to about 50% of the total after the infusion with [14C]cholic acid, while only about 10% with [14C]chenodeoxycholic acid. In the initial period of infusion, biliary conjugated [14C]bile acids consisted mostly of the taurine conjugate, which decreased with time and the glycine conjugate increased complementarily. When taurine was simultaneously infused, the decrease in the taurine conjugate was suppressed to some extent. Cysteine infused in place of taurine had a similar influence but was less effective than taurine. The taurine content of liver after the infusion with either of the [14C]bile acids decreased greatly compared with that before the infusion, even when taurine or cysteine was infused simultaneously. The glycine content also decreased after the infusion, but the decrease in glycine was smaller than that in taurine. The results suggest that the conjugate pattern of biliary bile acids in rats depends mainly on the amount of taurine which is supplied to hepatic cells either exogenously from plasma or endogenously within themselves.     

The ontogeny of physiological response to temperature in early stage spiny lobster (Jasus edwardsii) larvae

The physiological response to temperature, in terms of oxygen consumption, nitrogen excretion and feed intake was examined in Jasus edwardsii larvae at mid-stages I-III. From stage I to stage III, the mass-specific oxygen consumption increased in a sigmoid pattern over the temperature range of 10-22 degrees C. The Q(10) value declined significantly from 14-18 to 18-22 degrees C range, indicating a reduced temperature dependence of larval metabolism at higher temperatures. At all stages, feed intake increased with increasing temperature but reached a plateau at the higher temperatures for stages I and II larvae. In contrast, nitrogen excretion increased linearly over this temperature range for all larval stages. Therefore, higher temperatures ( approximately 22 degrees C) may cause an energetic imbalance and reduce growth potential in early stage larvae. While the convection requirement index (quotient of feed intake and oxygen consumption) indicated an equivalent metabolic feeding efficiency from 14 to 22 degrees C, a consistent decline of the O/N ratio above 16-18 degrees C from stage I to stage III suggested that exposure to elevated temperatures may result in an increase in the amount of protein being diverted from growth to catabolic processes. Based on these results, a temperature of 18 degrees C is recommended for the culture of early stage J. edwardsii larvae.     

Studies on flavonoid metabolism. Biliary and urinary excretion of metabolites of (+)-[U-14C]catechin

1. The biliary and urinary excretion of (+)-[U-(14)C]catechin was studied in normal male rats after a single injection of the flavonoid. 2. In rats large amounts of radioactivity (33.6-44.3% of the dose in 24h) were excreted in the bile as two glucuronide conjugates [one of which was a (+)-catechin conjugate] and three other unconjugated metabolites. 3. Excretion of radioactivity in the urine when the bile duct was not cannulated amounted to 44.5% of the dose. 4. In both the urine and bile the new metabolites showed maximum excretion in the (1/2)-1(1/2)h after intravenous injection of [(14)C]catechin. 5. The metabolites m-hydroxyphenylpropionic acid, p-hydroxyphenylpropionic acid, delta-(3-hydroxyphenyl)-gamma-valerolactone and delta-(3,4-dihydroxyphenyl)-gamma-valerolactione originate from the action of the intestinal micro-organisms on the biliary-excreted metabolites of (+)-catechin. These phenolic acid and lactone metabolites are then reabsorped and excreted in the urine. 6. It is proposed that, depending on the route of administration of (+)-catechin, there exists an alternative pathway, involving biliary excretion, for the metabolism of (+)-catechin.     

Androgen metabolism in the rhesus monkey.

A mixture of 3H-testosteron (T) and 14C-4-androstene-3, 17-dione (A) was injected intravenously into 2 (I and II) rhesus monkeys (Macaca mulatta). A third monkey (III) was injected with 3H-T only. Urine and bile samples were collected at intervals for 6 hours following the injection. The excretion, conjugation and aglycone metabolites of the steroids injected were studied using these samples. Of the injected dose, animal I (male) excreted 32% 3H and 23% 14C in the bile and 30% 3H and 21% 14C in the urine in 6 hours. Animal II (female), however, had a comparatively higher biliary excretion (66% 3H, 40% 14 C), but a urinary excretion (18% 3H, 13% 14C) comparable to that of animals I and III. The averages in the bile of the 3 animals were: unconjugated compounds 3%, glucosiduronates 78%, sulfates 9%, sulfoglucosiduronates 5% and disulfates 3%; and in urine, 5% unconjugated, 92% glucosiduronates and 3% sulfates. The aglycones obtained following hydrolysis were separated gy chromatography on Lipidex 5000, further purified by thin layer and paper chromatography and identified by co-crystallization. The major matabolites from 3H-T were androsterone and 5beta-androstane-3alpha,17beta-diol, whereas that from 14C-A was androsterone. Other metabolites identified were: etiocholanolone (3beta-hydroxy-5-beta-androstan-17-one); T, epitestosterone (epi-T), (17alpha-hydroxy-4-androsten-3-one); epiandrosterone (3-beta-hydroxy-5alpha-androstan-17-one) and 5alpha-androstane-3alpha, 17beta-diol. The results indicate that while androgen metabolism in the rhesus monkey is similar to that of the baboon and human in conjugate and metabolite formation, the rate of excretion was significantly different, resembline more closely that of the baboon than the human.     

Biliary excretion in foreign compounds. Species difference in biliary excretion

1. The biliary excretion of injected [¹⁴C]aniline, [¹⁴C]benzoic acid, 4-amino-hippuric acid and 4-acetamidohippuric acid in six or eight species of animal (rat, dog, hen, cat, rabbit, guinea pig, rhesus monkey and sheep) was studied. 2. These compounds, with molecular weights in the range 93–236, are poorly excreted in the bile in all the species examined and, in effect, there is little significant species difference in the extent of their biliary excretion. 3. Compounds of higher molecular weight (355–495) were also studied, namely succinylsulphathiazole, [¹⁴C]stilboestrol glucuronide, sulphadimethoxine N¹-glucuronide and phenolphthalein glucuronide. 4. With these compounds a clear species difference in the extent of biliary excretion was found, the rat, dog and hen being good excretors, the rabbit, guinea pig and monkey poor excretors, and the cat and sheep taking an intermediary position. 5. There was a general trend for biliary excretion to be higher in all species when the compounds were of higher molecular weight. 6. These results are discussed in their relation to species differences in drug metabolism.     

Metabolism and excretion of exogenous [3H]-LTC4 in primates

Four novel omega- and beta-oxidation (from the omega end) products of peptide leukotrienes, 20-hydroxy and 20-carboxy-LTE4, 18-carboxy-19, 20-dinor-LTE4 and 16-carboxy-17,18,19,20-tetranor-14,15-dihydro-LTE4 were prepared by total synthesis and used as standards for identification of biliary and urinary metabolites in the cynomolgus monkey. After intravenous administration 14, 15-[3H] leukotriene C4 (10 microCi kg-1) was partially metabolized in and rapidly cleared from the vascular circulation. This resulted, within 24 hours, in significant urinary excretion (14.8 +/- 2.1%, n = 4), consisting largely of material more polar than LTE4 (61% of urinary excretion) as shown by reverse phase HPLC. The polar fraction demonstrated two predominant metabolites which coeluted in several HPLC solvent systems with synthetic 16-carboxytetranordihydro-LTE4 (major component) and 18-carboxydinor-LTE4 (minor component). Characterization of the major polar metabolite as 16-carboxytetranordihydro-LTE4 was substantiated by conversion to its N-acetylated derivative. The absence of the 14, 15 double bond was confirmed by product analysis of oxidative ozonolysis. In a single animal, the bile duct was cannulated, with significant biliary excretion of radioactivity demonstrated over 4 hours (58.6% recovery). The predominant polar biliary metabolites were also identified as the 18-carboxydinor and 16-carboxytetranordihydro derivatives of LTE4 mentioned above. These data suggest that beta-oxidation products generated from the omega-carboxyl end of the 20-carboxy-LTE4 are important products of [3H] LTC4 metabolism in the monkey. Quantitation of these urinary metabolites may be an important index of in vivo leukotriene production.     

Effect of 3-methylcholanthrene on the biliary excretion of bromsulphthalein and eosine in newborn rats.

The biliary excretion rates of bromsulphthalein (BSP), bromsulphthalein-glutathione conjugate (BSP-GSH) and eosine have been studied in 3-methylcholanthrene (3-MC)-pretreated (100 mg/kg i.p.) and control rats aged 10 days. Liver weight was invariably increased after 3-MC treatment, associated with enhanced biliary excretion of total BSP. The increase in the biliary excretion of total BSP was due solely to the increased excretion of BSP-GSH. Following 3-MC pretreatment, BSP-GSH and eosine appeared in the bile in the same amount as in the control rats after i.v. administration of BSP-GSH and eosine. Pretreatment with 3-MC increased the ratio of BSP-GSH to BSP in the liver and bile. Our results suggest that the increased biliary excretion of total BSP following 3-MC treatment was due to an enhanced conjugation of BSP with GSH.     

Biliary excretion of foreign compounds. Benzene and its derivatives in the rat

1. The extent of the excretion in the bile of the rat of benzene and 21 of its simple derivatives was studied. 2. Some 16 compounds of molecular weight less than 200, and including neutral molecules (benzene and toluene), aromatic acids, aromatic amines and phenols, were injected in solution intraperitoneally into biliary-cannulated rats. Metabolites in the bile were identified and estimated. The extent of biliary excretion of these compounds was low, i.e. 0–10% of the dose in 24hr., and most appeared in the bile mainly as conjugates. 3. The biliary excretion of six conjugates of molecular weight less than 300, including three glycine conjugates, one sulphate conjugate, one glucuronic acid conjugate and two acetyl derivatives, was low (less than 3% of the dose). 4. It is concluded that simple benzene derivatives of molecular weight less than about 300 are poorly excreted in rat bile.     

Glutathione conjugation and pharmacokinetics of 2-bromo-3-phenylpropionic acid in vitro and in the rat in vivo.

Glutathione (GSH) conjugation of the chiral compound 2-bromo-3-phenylpropionic acid (BPP) was studied in vitro and in the rat in vivo. GSH conjugation of BPP, catalyzed by a mixture of glutathione-S-transferases (GST's) from rat liver cytosol in vitro, was stereoselective: at a substrate concentration of 250 microM, (R)-BPP was more rapidly conjugated than (S)-BPP (R/S-ratio = 2.6). The blood elimination kinetics of the separate BPP enantiomers and the biliary excretion kinetics of the corresponding GSH conjugates were studied in the rat in vivo after administration of (R)- or (S)-BPP at a dose level of 50 mumol/kg. Elimination of (R)-BPP from blood was faster than that of (S)-BPP: half lives were 9 +/- 2 min for (R)-BPP and 13 +/- 1 min for (S)-BPP. The biliary excretion rate of the GSH conjugate of (R)-BPP declined monoexponentially, while that of the GSH conjugate of (S)-BPP displayed a biphasic profile. Half lives of excretion were 13 +/- 1 for the GSH conjugate of (R)-BPP, and 11 +/- 2 for the GSH conjugate of (S)-BPP (second phase). The first phase in the biliary excretion of the GSH conjugate of (S)-BPP could not be attributed to capacity limitation of biliary transport carriers as higher excretion rates were attained upon administration of higher doses (100 and 200 mumol/kg) of (S)-BPP). The blood elimination profiles of (R)- and (S)-BPP differed greatly from the biliary excretion profiles of the corresponding GSH conjugates. This suggests that the kinetics of BPP conjugate excretion are determined by other processes than hepatic GSH conjugation.     

Biliary excretion of some diquaternary ammonium cations in the rat, guinea pig and rabbit

1. The extent of the excretion in the bile and urine of the (14)C-labelled dications, diquat, paraquat, morfamquat, decamethonium and dimethyltubocurarine in bile-duct-cannulated rats, guinea pigs and rabbits was examined. 2. These compounds were excreted unchanged in bile and urine, except diquat, which was metabolized to a significant extent (18% of the dose) in the rabbit only. 3. The extent of the biliary excretion of diquat (mol wt. of ion 184), paraquat (186), decamethonium (258) and morfamquat (469) was less than 10% of the dose in the three species, whereas that of dimethlytubocurarine (653) was greater than 10% in the rat and rabbit but not in the guinea pig. 4. These results together with data from the literature suggest that the molecular weight at which the excretion of dications in the bile exceeds 10% of the dose is in the region of 500-600, which differs from the values for monocations (Hughes et al., 1973) and anions (Millburn et al., 1967; Hirom et al., 1972).     

Incorporation into phospholipid classes and metabolism via desaturation and elongation of various 14C-labelled (n-3) and (n-6) polyunsaturated fatty acids in trout astrocytes in primary culture

The incorporation and metabolism of [1-14C]18:3(n-3), [1-14C]20:5(n-3), [1-14C]18:2(n-6), and [1-14C]20:4(n-6) were studied in primary cultures of trout brain astrocytes. There were no significant differences between the amounts of individual fatty acids incorporated into total lipid at 22 degrees C, with greater than 90% of all the fatty acids being incorporated into polar lipid classes. The distributions of 18:2(n-6), 18:3(n-3), and 20:5(n-3) in individual phospholipid classes at 22 degrees C were very similar, with 57-63 and 18-24% being incorporated into phosphatidylcholine and phosphatidylethanolamine, respectively. Approximately equal amounts of 20:4(n-6), approximately 30% of the total, were incorporated into each of phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol. The metabolism of the (n-3) fatty acids to longer-chain and more unsaturated species was significantly greater than that of (n-6) acids, but delta 4-desaturase activity was very low. A culture temperature of 10 degrees C increased the incorporation of all the fatty acids into total lipid and that of C20 fatty acids into polar lipid. At 10 degrees C, the incorporation of C20 fatty acids into phosphatidylethanolamine and phosphatidylinositol was increased, and the incorporation into phosphatidylcholine and phosphatidylserine was decreased. The distribution of C18 fatty acids was unchanged at the lower temperature, as was the desaturation and elongation of all the polyunsaturated fatty acids incorporated.     

Molecular weight as a factor in the excretion of monoquaternary ammonium cations in the bile of the rat, rabbit and guinea pig

1. The excretion in the bile and urine of intraperitoneally injected (14)C-labelled monoquaternary ammonium or pyridinium cations was measured in bile-duct-cannulated rats (ten compounds) and in guinea pigs and rabbits (six compounds). 2. Seven of these, namely N-methylpyridinium, tetraethylammonium, trimethylphenylammonium, diethylmethylphenylammonium, methylphenyldipropylammonium, dibenzyldimethylammonium and tribenzylmethylammonium, were excreted largely unchanged in the bile and urine. 3. 3-Hydroxyphenyltrimethylammonium, 3-bromo-N-methylpyridinium and cetyltrimethylammonium were metabolized to an appreciable extent in the rat. 4. In intact rats intraperitoneally injected trimethylphenylammonium (mol.wt. 136) was excreted mainly in the urine, dibenzyldimethylammonium (mol.wt. 226) was excreted in roughly equal amounts in the urine and faeces, and tribenzylmethylammonium (mol.wt. 302) was excreted mainly in the faeces. The faecal excretion of these compounds corresponded to their biliary excretion in bile-duct-cannulated rats. About 3-4% of tribenzyl[(14)C]methylammonium was eliminated as (14)CO(2). 5. In rats the extent of biliary excretion of four cations with molecular weights in the range 94-164 was less than 10% of the dose, whereas that of five cations with molecular weights 173-302 was greater than 10%. These results and other data from the literature suggested that the molecular weight needed for the biliary excretion of such cations to an extent of 10% or more of the dose was about 200+/-50. Studies with six cations in guinea pigs and rabbits suggest that this value applies also to these species. 6. The results suggest that the threshold molecular weight for the appreciable (>10%) biliary excretion of monoquaternary cations is different from that for anions (Millburn et al., 1967a; Hirom et al., 1972b). With rats, guinea pigs and rabbits, no significant species difference was noted, whereas with anions there is a marked species difference.     

Role of the hepatocyte microtubular system in the excretion of bile salts and biliary lipid: implications for intracellular vesicular transport

The role of the hepatocyte microtubular system in the transport and excretion of bile salts and biliary lipid has not been defined. In this study the effects of microtubule inhibition on biliary excretion of micelle- and non-micelle-forming bile salts and associated lipid were examined in rats. Low-dose colchicine pretreatment had no effect on the baseline excretion of biliary bile salts and phospholipid in animals studied 1 hr after surgery (basal animals), but slightly retarded the excretion of tracer [14C]taurocholate relative to that of lumicolchicine-pretreated (control) rats. However, colchicine pretreatment resulted in a marked reduction in the excretion of 2 mumol/100 g doses of a series of four micelle-forming bile salts of differing hydrophilicity, but had no significant effect on the excretion of the non-micelle-forming bile salt, taurodehydrocholate. Continuous infusion of 0.2 mumol of taurocholate/(100 g.min) following 24 hr of biliary drainage (depleted/reinfused animals) resulted in physiologic bile flow with biliary excretion rates of bile salts, phospholipid, and cholesterol that were markedly inhibited (mean 33, 39, and 42%, respectively) by colchicine or vinblastine pretreatment. Excretion of tracer [14C]taurocholate also was markedly delayed by colchicine in these bile salt-depleted/reinfused animals. In contrast, colchicine did not inhibit bile salt excretion in response to reinfusion of taurodehydrocholate. Thus, under basal conditions, the microtubular system appears to play a minor role in hepatic transport and excretion of bile salts and biliary lipid. However, biliary excretion of micelle-forming bile salts and associated phospholipid and cholesterol becomes increasingly dependent on microtubular integrity as the transcellular flux and biliary excretion of bile salts increases, in both bile salt-depleted and basal animals. We postulate that cotransport of micelle-forming bile salts and lipids destined for biliary excretion, via an intracellular vesicular pathway, forms the basis for this microtubule dependence.     

Effect of ursodeoxycholate on the bile flow in the rat

The relationship between the bile flow and biliary excretion rate of bile salt was studied by a continuous infusion of ursodeoxycholate and its glycine conjugate in rats. Infusion of glycoursodeoxycholate produced a higher flow rate and higher bile salt concentration than previously reported values for taurocholate. The estimated biliary transport maximum value was 2.21±0.15 μmole/min/100g body weight (mean±SD, N=13). Furthermore, a linear relation was found between the bile flow and bile salt excretion rate for a wide range of bile salt excretion with a slope value of 4.10±0.64 μl/μmole (N=10). These values were close to values previously reported for tauroursodeoxycholate. In contrast, when free ursodeoxycholate was infused, a bile salt excretion rate increased at first to a level of around 1.0 μmole/min/100g body weight with a concomitant bile flow increase, but after one hr, the bile salt excretion dropped sharply and a lower plateau of about half of the initial maximum level was established in the following hr. On the other hand, the bile flow further increased even in the second hr. Consequently, the linear relationship initially observed between the bile flow and bile salt excretion rate became gradually distorted and after one hr even the positive correlation between the two parameters was completely lost. The sharp drop in the bile salt excretion rate was found to be due to the decrease in the taurine conjugate of ursodeoxycholate in the bile. The excretion rate of free ursodeoxycholate remained at a very low level (about 0.1 μmole/min/100g body weight) throughout the experiments. The concentration of ursodeoxycholate in the liver increased sharply in the second hr corresponding to the decrease in the bile salt excretion rate. These results appear to be most easily explained by the thesis that there is a fraction of bile independent of bile salt excretion but dependent on the bile salt concentration in the hepatocyte.     

The incorporation of unsaturated fatty acids of the n-9, n-6, and n-3 families into individual phospholipids by isolated hepatocytes of thermally-acclimated rainbow trout, Salmo gairdneri

Rates of incorporation of 1-14C-oleic (18:1n9), -linoleic (18:2n6), and -linolenic (18:3n3) acids into individual phosphatides were determined in isolated hepatocytes from cold (5 degrees C)- and warm (20 degrees C)-acclimated rainbow trout, Salmo gairdneri. Fatty acid incorporation into phosphatidylcholine (PC) exceeded that into all other phospholipids, but at assay and acclimation temperatures of 5 degrees C, incorporation into phosphatidylethanolamine (PE) was generally intermediate between that of PC and the remaining phosphatides. Specific radioactivities (ratios of percentage isotope incorporation-to-mole percentage of phosphatide) were consistently less than one for both PC and PE, and greater than one for phosphatidic acid (PA), lysophosphatidylcholine (LPC), phosphatidylserine (PS), and cardiolipin (CL). For PS, specific radioactivities were greater in cold- than warm-acclimated trout, and greater at 5 degrees C than 20 degrees C. Rates of oleate incorporation were generally higher, and rates of incorporation of 18:2 and 18:3 lower in cold- than warm-acclimated trout. Most phospholipids demonstrated a clear preference for the incorporation of 18:2 when assayed at 20 degrees C; however, at 5 degrees C the incorporation of 18:2 was reduced and 18:3 was generally the preferred substrate. A reduction in assay temperature from 20 degrees C to 5 degrees C also shifted the incorporation of 18:2 away from PC into PS and PA. These data were interpreted to indicate 1) a cold-induced activation of PS metabolism, possibly resulting in elevated levels of PE; 2) lower rates of general acyl group turnover in animals acclimated to 5 degrees C than 20 degrees C; 3) a specificity to the acclimation response that favors the incorporation at cold temperatures of polyunsaturated fatty acids, but not the parent acids from which they are derived; and 4) the participation of a deacylation-reacylation cycle in the metabolism of phospholipids, particularly at cold temperatures.     

Sweat lactate in exercising children and adolescents of varying physical maturity.

This study attempts to explain some of the individual variability in sweating pattern by comparing prepubescents and pubescents. Sweating rate and muscular anaerobic capacity are higher in adults than in children; thus we hypothesized that sweat gland anaerobic metabolism, as reflected by lactate excretion, might be higher with advanced physical maturity (PM). Lactate concentration in sweat ([LAC]sw) was measured at various stages of PM in boys who exercised in the heat. The subjects were divided into three groups on the basis of Tanner staging: prepubertal (PP, n = 16), midpubertal (MP, n = 15), and late pubertal (LP, n = 5). Subjects cycled at 50% of maximal O2 uptake for three 20-min bouts, with 10-min rest periods, in 42 degrees C and 18% relative humidity. Sweat samples were harvested, and population density of activated sweat glands was determined after each exercise bout. [LAC]sw during bout 1 was higher in PP than in LP [PP = 22.2 +/- 2.2, MP = 19.5 +/- 1.4, LP = 14.3 +/- 1.3 (SE) mmol/l]. In all groups, [LAC]sw decreased during subsequent bouts, and there were no intergroup differences in [LAC]sw during bout 3 (PP = 11.2 +/- 0.4, MP = 10.6 +/- 0.5, LP = 9.7 +/- 0.2 mmol/l). [LAC]sw was inversely related to sweating rate. Lactate excretion rate per gland was greater with the increase in PM (PP = 61.0 +/- 8.2, MP = 79.1 +/- 11.3, LP = 99.9 +/- 11.0 pmol/min; P = 0.08).(ABSTRACT TRUNCATED AT 250 WORDS)     

栉孔扇贝耗氧率和排氨率的研究

1999年 4～ 6月 ,采用室内实验生态学方法对栉孔扇贝的耗氧率和排氨率进行了研究 .结果表明 ,在适宜的温度范围内 ,栉孔扇贝的耗氧率和排氨率均与温度成正比 ,而与体重呈负相关关系 .在实验室温度 (8～ 2 8℃ )条件下 ,栉孔扇贝的耗氧率为 0 .48～ 9.0 9mg·g-1·h-1,排氨率为 0 .0 5～ 1 0 1mg·g-1·h-1.其中耗氧率在 2 3℃时达到最高值 ,2 8℃时开始下降 ,而排氨率则呈持续升高趋势 .栉孔扇贝的日常代谢明显高于标准代谢 ,耗氧率和排氨率平均值分别提高约 35 .8%和 75 .9% .     

Cholesterol gallstones in alloxan-diabetic mice

Normal and alloxan-diabetic male mice (Crj-ICR) were fed a diet containing 0.5% cholesterol for 5 and 10 weeks, and gallbladder bile was analyzed for cholesterol, phospholipids and bile acids, feces for sterols and bile acids, and plasma and liver for cholesterol, phospholipids, and triglycerides. Normal mice developed no gallstones but the diabetic mice developed cholesterol gallstones with an incidence of 70% by 5 weeks and 80% by 10 weeks after feeding of the cholesterol diet. Diabetic mice fed the ordinary diet also developed stones (23%) by 10 weeks. In the diabetic mice, the gallbladder was enlarged about threefold, and biliary lipid concentration, diet intake, and fecal excretion of sterols and bile acids increased but body weight decreased. Cholic acid and beta-muricholic acid comprised over 40% each of the total biliary bile acids in normal mice, but cholic acid increased to about 80% and beta-muricholic acid decreased to a few percent in the diabetic mice. Fecal excretion of bile acids increased after cholesterol feeding in both normal and diabetic mice, but the increased bile acid in the normal animals was beta-muricholic acid and that in the diabetic mice was deoxycholic acid. The mice that developed gallstones showed a marked increase in biliary cholesterol value and decreases in gallbladder bile and bile acid concentration, but no difference in biliary and fecal bile acid composition, bile acid synthesis, fecal sterols, or plasma and liver lipid levels. Cholesterol absorption was increased in the diabetic mice when examined by plasma 14C/3H ratio and fecal 14C-labeled sterol excretion after a single oral administration of [14C]cholesterol and a simultaneous intravenous injection of [3H]cholesterol. These data led to the conclusion that cholesterol gallstones developed in alloxan-diabetic mice fed excess cholesterol, due to the hyperphagia and the enhancement of cholesterol absorption caused by increases in the synthesis and secretion of cholic acid.     

In vivo and in vitro metabolism of gomphoside, a cardiotonic steroid with doubly-linked sugar

The metabolism of gomphoside, a cardiotonic steroid glycoside with doubly-linked 4,6-dideoxyhexosulose sugar was studied in vivo in rats, and in vitro using rat liver microsomes. The biliary excretion of metabolites, following intraperitoneal administrative of [3H]gomphoside, was rapid with 68% of radioactivity being collected over 8 h. The metabolites in the bile were principally a water-soluble glucuronide conjugate of gomphoside, and a small amount of chloroform-soluble metabolites. Conversion of [3H]gomphoside to metabolites by microsomes at 37 degrees C reached a maximum of 16% under optimum conditions, producing the same set of metabolites as those in the chloroform-soluble fraction of the bile. The major chloroform-soluble metabolite was the aglycone of gomphoside, viz. gomphogenin or 2 alpha,3 beta, 14-trihydroxy-5 alpha-card-20(22)-enolide. The other major component was recovered gomphoside. Other metabolites were calactin, calotropin, and 2 alpha-hydroxyuzarigenin 3-(4,6-dideoxy-beta-D-arabino-hexopyranoside). Another metabolite, which is a new cardenolide was shown to be 3-epi-gomphogenin or 2 alpha,3 alpha, 14-trihydroxy-5 alpha-card-20(22)-enolide. Gomphoside glucuronide was shown spectroscopically to have the glucuronide residue attached to position 3' of the hexosulose sugar. It was cleaved by beta-D-glucuronidase to gomphoside, and is thus gomphoside 3'-beta-D-glucuronide. The metabolic transformations of gomphoside are summarized in Fig. 5.