Evaluation of a receptor gene responsible for maternal blood IgY transfer into egg yolks using bursectomized IgY-depleted chickens.

In avian species, maternal immunoglobulin Y (IgY) is transferred from the blood to the yolks of maturing oocytes; however, the mechanism underlying this transfer is unknown. To gain insight into the mechanisms of maternal IgY transfer into egg yolks, IgY-depleted chickens were generated by removing the bursa of Fabricius (bursectomy) during egg incubation, and their egg production and IgY transport ability into egg yolks were determined. After hatching, blood IgY concentrations of the bursectomized chickens decreased gradually until sexual maturity, whereas those of IgA remained low from an early stage of growth (from at least 2 wk of age). Chickens identified as depleted in IgY through screening of blood IgY and IgA concentrations were raised to sexual maturity. At 20 wk of age, both blood and egg yolk IgY concentrations in the IgY-depleted group were 600-fold lower than those of the control group, whereas egg production did not differ between the groups. Intravenously injected, digoxigenin-labeled IgY uptake into the egg yolk was approximately 2-fold higher in the IgY-depleted chickens than in the controls, suggesting that IgY depletion may enhance IgY uptake in maturing oocytes. DNA microarray analysis of the germinal disc, including the oocyte nucleus, revealed that the expression levels of 73 genes were upregulated more than 1.5-fold in the IgY-depleted group, although we could not identify a convincing candidate gene for the IgY receptor. In conclusion, we successfully raised IgY-depleted chickens presenting a marked reduction in egg yolk IgY. The enhanced uptake of injected IgY into the egg yolks of the IgY-depleted chickens supports the existence of a selective IgY transport mechanism in maturing oocytes and ovarian follicles in avian species.

Higher incorporation of heterologous chicken immunoglobulin Y compared with homologous quail immunoglobulin Y into egg yolks of Japanese quail (Coturnix japonica).

In avian species, blood IgY is selectively incorporated into the yolks of maturing oocytes, although the precise mechanism is poorly understood. Our previous study showed that 22% of i.v.-injected heterologous chicken IgY (cIgY) was incorporated into egg yolks of Japanese quail (Coturnix japonica). However, it is not known whether homologous quail IgY (qIgY) can be more efficiently incorporated into quail egg yolks than cIgY. Therefore, we compared the uptakes of qIgY and cIgY i.v. administered into quail egg yolks and further characterized the uptakes of these 2 antibodies into quail ovarian follicles. Quail IgY and cIgY purified from the blood of the respective bird were labeled with digoxigenin, and their uptakes into quail egg yolks were determined by ELISA. Unexpectedly, total incorporation of the injected qIgY was only one-third of that of cIgY, although much more qIgY was left in blood compared with cIgY, suggesting that qIgY is the less preferable antibody as a transport ligand into quail egg yolks. On the other hand, deposition of the qIgY into heart, lung, liver, spleen, kidney, and ovarian follicular membrane was markedly higher than that of cIgY. Amino acid sequence analysis of 3 peptides derived from the trypsin-digested qIgY heavy chain revealed low homology between qIgY and cIgY. In conclusion, our results show that heterologous cIgY is more efficiently incorporated into quail egg yolks than homologous qIgY, possibly due to a distinctive antibody transport system existing in oocytes. The present results also may provide a new strategy for delivering useful proteinaceous substances into egg yolks in an attempt to produce designer eggs.

Ingestion of paddy rice increases intestinal mucin secretion and goblet cell number and prevents dextran sodium sulfate-induced intestinal barrier defect in chickens.

Paddy rice is a potential feed grain for chickens, whose strong gizzards can crush the hull. Here, we investigated whether paddy rice rich in hull-derived water-insoluble dietary fiber stimulates intestinal mucin secretion and production, as well as the possible involvement of paddy rice in intestinal barrier function. Layer male chicks at 7 d of age were divided into four groups according to the diet: corn, polished rice, brown rice, or paddy rice (650 g/kg diet), which they ate for 14 consecutive days. At 21 d of age, the birds were refed their experimental diets, and small intestinal mucin fractions were collected to determine intestinal mucin content. Small intestinal mucin secretion was induced most strongly in the paddy rice group (Experiment 1). The rank order of diet-induced mucin secretion was paddy rice > corn = brown rice > polished rice. Ileal MUC2 gene expression and ileal number of goblet cells were highest in the paddy rice group (Experiment 1). A study of bromodeoxy-U uptake into ileal epithelial cells indicated the increase in goblet cells in the paddy rice group was related to accelerate epithelial cell migration (Experiment 2). A single supplementation of isolated rice hulls without kernels increased MUC2 gene expression and goblet cell numbers (Experiment 3), suggesting the importance of the hull's bulk-forming capacity on mucin production. Finally, chicks fed corn or paddy rice were orally administered dextran sodium sulfate (DSS) to disrupt intestinal barrier function. In the DSS-treated birds, the intestinal permeability of fluorescein isothiocyanate dextran in the everted gut sacs was much lower in the paddy rice group than in the corn group (Experiment 4), showing that paddy rice protects against mucosal disruption. In conclusion, ingestion of paddy rice increases intestinal mucin secretion and production through enhanced MUC2 gene expression and epithelial turnover and prevents DSS-induced intestinal barrier defects in chickens.

Absorption and metabolism of cyanidin 3-O-beta-D-glucoside in rats.

We have clarified for the first time how cyanidin 3-O-beta-D-glucoside (C3G), which is a potent antioxidant anthocyanin, is absorbed and metabolized in vivo. Rats were orally administered C3G (0.9 mmol/kg body weight), and C3G rapidly appeared in the plasma. However, the aglycon of C3G (cyanidin; Cy) was not detected, although it was present in the jejunum. Protocatechuic acid (PC), which may be produced by degradation of Cy, was present in the plasma and the concentration was 8-fold higher than that of C3G. These results suggest that plasma PC and C3G may contribute to the antioxidant activity of the plasma. In the liver and kidney, C3G was metabolized to methylated C3G (methyl-C3G), suggesting that C3G and/or methyl-C3G act as antioxidants in the tissues.

Acute nephrotoxicity of a carcinogenic iron chelate. Selective inhibition of a proteolytic conversion of alpha 2U-globulin to the kidney fatty acid-binding protein.

The mechanism of acute nephrotoxicity of an iron chelate in vivo has been investigated. Administration of a renal carcinogen ferric nitrilotriacetate (Fe-NTA) (15 mg Fe/kg body weight, intraperitoneally) led to selective loss of a renal protein with an apparent molecular mass of 17 kDa. Analysis of the 17 kDa protein by NH2-terminal sequence demonstrated its identity over 16 NH2-terminal residues as a kidney fatty acid-binding protein (k-FABP) that is a proteolytically modified form of alpha 2U-globulin, a major urinary protein of adult male rats. An immunochemical study using anti-alpha 2U-globulin polyclonal antibodies confirmed that a single injection of Fe-NTA led to a decrease in k-FABP levels. However, a 19-kDa protein identical to the alpha 2U-globulin progressively appeared in the kidney, suggesting that the proteolytic processing of alpha 2U-globulin in the renal proximal tubules was suppressed by the treatment with Fe-NTA. By monitoring k-FABP and its precursor alpha 2U-globulin, it was determined that repeated exposure to Fe-NTA caused suppression of both proteolytic and endocytotic activity of the kidney. The implications of these data in relation to the nephrotoxicity of Fe-NTA are discussed.

Antiplatelet and anticancer isothiocyanates in Japanese domestic horseradish, Wasabi.

6-Methylsulfinylhexyl isothiocyanate (MS-ITC) was isolated from wasabi (Wasabia japonica, Japanese domestic horseradish) as a potential inhibitor of human platelet aggregation in vitro through our extensive screening of vegetables and fruits. In the course of an another screening for the induction of glutathione S-transferase (GST) activity in RL34 cells, MS-ITC was inadvertently isolated from wasabi as a potential inducer of GST. MS-ITC administered to rats or mice also showed both activities in vivo. As a result from elucidation of the platelet aggregation inhibition and the GST induction mechanisms of MS-ITC, the isothiocyanate moiety of MS-ITC plays an important role for antiplatelet and anticancer activities because of its high reactivity with sulfhydryl (RSH) groups in biomolecules (GSH, cysteine residue in a certain protein, etc.).

Increase in production of ascorbate radical in tissues of rat treated with paraquat.

The production of ascorbate radical (A*-) was investigated in tissues of rats intoxicated with paraquat (PQ) to know the protective role of antioxidant ascorbate (AH-) in tissues. The electron spin resonance (ESR) method is applied to observe A*-. To eliminate increased biosynthesis of ascorbic acid (AH2) by PQ intoxication, ODS rats were chosen and fed with or without 250 ppm PQ in the diet. The radical A*- was detected only in the lung and spleen homogenates of both intoxicated and control rats at the beginning of ESR measurement. The radical levels of intoxicated rat lung and spleen were increased rapidly to twice the initial level after 3 h and decreased to 0.2-0.6 times the initial level after 24 h, whereas those of control rats were increased slowly to 1.1 times the initial level after 4 h and decreased slowly to 0.7 times the initial level after 24 h at 4 degrees C. In other organs such as liver, kidney, heart and testis, A*- was not detected initially but detected afterwards. Higher A*- level was observed in the intoxicated rat liver than the control but no appreciable differences of A*- levels were observed between the intoxicated kidney, heart and testis and the respective controls. In the intoxicated rat lung the concentration of AH2 is only half but that of A*- is twice as high as that of the control. Larger amounts of A*- produced in the intoxicated rats decayed more quickly than those in the control rats. The simple addition of PQ to the control organ enhanced neither A*- production nor A*- quenching. These facts suggest that the tissues damaged by PQ require larger amounts of AH- to detoxicate harmful oxidants, resulting in concomitant production of A*-.

Fatty liver and hyperlipidemia in IDDM (insulin-dependent diabetes mellitus) of streptozotocin-treated shrews.

Severe IDDM (insulin-dependent diabetes mellitus) was produced in the musk shrew (Suncus murimus, Insectivora) by a high dose (a single intraperitoneal injection of 100 mg/kg Body Weight) of streptozotocin (STZ) injection. All shrews that were administered a high dose of STZ exhibited hyperglycemia (449 +/- 16 mg/dl vs 73 +/- 4 mg/dl in controls) and hypoinsulinemia(0.25 +/- 0.07 ng/ml vs 10.96 +/- 1.97 ng/ml in controls) with ketosuria 10 days after injection. Their livers were enlarged and exhibited ayellowish-brown color with marked triglyceride (TG) accumulation (63.25 +/- 7.10 mg/g Liver vs 2.11 +/- 0.19 mg/g Liver in controls). It is probable that the increased influx of fatty acids into the liver induced by hypoinsulinemia and the low capacity of excretion of lipoprotein secretion from liver in the musk shrew resulting from a deficiency of apolipoprotein B synthesis play important roles in fatty liver formation. Hyperlipidemia was another feature in shrews with severe IDDM. The blood TG level was especially high in these shrews (899 +/- 178 mg/dl vs 23 +/- 5 mg/dl in controls). These results indicate that the IDDM shrew, induced by high doses of STZ, is a unique model characterized by fatty liver and hyperlipidemia and may be useful for studying lipid metabolism of IDDM.

Toxin-induced IDDM (insulin dependent diabetes mellitus) in the musk shrew.

We administered streptozotocin (STZ) and alloxan (AL) to the musk shrew (Suncus murinus, Insectivora) to determine the effective diabetogenic dose of the two toxins for this species. A single intraperitoneal (i.p.) injection of 75 mg/kgBW or the consecutive 5-day s injection of 25 mg/kgBW of STZ to non-fasted shrews, effectively (100%) induced hyperglycemia (> or = 300 mg/dl) with hypoinsulinaemia (< 30% of control level) in male shrews at 10 days after administration. Morphological studies showed cytological changes of B cells in the pancreatic islets of diabetic shrews. Hyperglycemic shrews induced by STZ were thus in IDDM (insulin dependent diabetes mellitus), and showed high susceptibility to the diabetogenic effect of STZ as compared with rodents. Shrews showed a sex difference in the diabetogenic susceptibility to STZ as do mice (male > female). They also showed a species specific resistance to the diabetogenic effect of AL. Of the eight shrews (with 8-hr fasting) that has been treated with a single injection of 200 mg/kgBW of AL, seven (88%) survived at least 10 days, showing no signs of hyperglycemia. All shrews died within 3 day s after injection of 250 or 300 mg/kgBW. These results indicated that the STZ-induced diabetic shrew is a unique animal model and may be useful for IDDM research. On the other hand, the musk shrew was highly resistant to the diabetogenic effects of AL.

A newly established strain of spontaneously hypertensive rat with a defect of ascorbic acid biosynthesis.

To investigate the effects of ascorbic acid deficiency on the pathogenesis of hypertension and/or its complications, we established a rat strain with both genetic hypertension and a defect of ascorbic acid biosynthesis. The od gene (L-gulono-gamma-lactone oxidase gene) of the ODS (Osteogenic Disorder Shionogi) rat, which is a rat mutant unable to synthesize ascorbic acid, was introduced into spontaneously hypertensive rats (SHR), and a novel congenic strain, SHR-od, was established. SHR-od showed scurvy when fed an ascorbic acid-free diet. Systolic blood pressure of male SHR-od began to increase at 9 weeks of age and reached 190-200 mmHg at 20 weeks of age. In 25-week-old SHR-od, ascorbic acid deficiency when fed an ascorbic acid-free diet for 6 weeks caused a remarkable reduction of blood pressure to lower than 110 mmHg. The wall to lumen ratio of the testicular artery in ascorbic acid-deficient SHR-od was lower than that of the control rats. When rats were fed a diet supplemented with ascorbic acid (300 mg/kg), ascorbic acid concentration in SHR-od was lower in the serum and liver than that in ODS rats. These results indicate that ascorbic acid could be closely related to the development of hypertension in SHR-od. We believe that SHR-od will be a useful model for experimental studies on hypertension and its complications, since all of them suffer from hypertension spontaneously and the level of ascorbic acid deficiency in these rats could be controlled at will both in concentration and duration.

Dietary cyanidin 3-O-beta-D-glucoside increases ex vivo oxidation resistance of serum in rats.

The effect of dietary cyanidin 3-O-beta-D-glucoside (C3G), a typical anthocyanin pigment, on the generation of thiobarbituric acid reactive substances (TBARS) during serum formation ex vivo and susceptibility of serum to further lipid peroxidation was studied in rats. Rats were fed a diet containing C3G (2 g/kg) for 14 d. Feeding C3G resulted in a significant decrease in generation of TBARS during serum formation. The serum from the C3G-fed group showed a significantly lower susceptibility to further lipid peroxidation provoked by 2,2'-azobis(2-amidinopropane)hydrochloride or Cu2+ than that of the control group. No significant differences were observed in serum phospholipid, triglyceride, esterified cholesterol, and free fatty acid concentrations between the control and the C3G-fed groups. Concentrations of endogenous antioxidants remaining in the serum after blood coagulation were not affected by the C3G feeding. These results demonstrate that feeding C3G increases the ex vivo oxidation resistance of the serum without affecting serum endogenous antioxidant levels, and reduces the TBARS generated during serum formation without changing the concentrations of serum lipids.

The role of anthocyanins as an antioxidant under oxidative stress in rats.

Cyanidin 3-O-beta-D-glucoside (C3G) is included in anthocyanins, and expected to have a potency to scavenge active oxygen species in vivo. Rats were fed a diet containing C3G (2 g/kg diet) for 14 days, and then subjected to hepatic ischemia-reperfusion (I/R) as an oxidative stress model. I/R treatment elevated the liver thiobarbituric acid-reactive substance concentration and the serum activities of marker enzymes for liver injury, and lowered the liver reduced glutathione concentration. Feeding C3G significantly suppressed these changes caused by hepatic I/R. These results indicate that C3G functions as a potent antioxidant in vivo under oxidative stress. To clarify the mechanism of action of C3G, we investigated the absorption and metabolism of C3G in rats. C3G appeared in the plasma immediately after the oral administration of C3G. Protocatechuic acid, which seems to be produced by the degradation of cyanidin, was also present in the plasma. In the liver and kidneys, C3G was metabolized to methylated form.

Antiplatelet and anticancer isothiocyanates in Japanese domestic horseradish, wasabi.

6-Methylsulfinylhexyl isothiocyanate (MS-ITC) was isolated from wasabi (Wasabia japonica, Japanese domestic horseradish) as a potential inhibitor of human platelet aggregation in vitro through our extensive screening of vegetables and fruits. In the course of another screening for the induction of glutathione S-transferase (GST) activity in RL34 cells. MS-ITC was inadvertently isolated from wasabi as a potential inducer of GST. MS-ITC administered to rats or mice also showed both activities in vivo. As a result from elucidation of the platelet aggregation inhibition and the GST induction mechanisms of MS-ITC, the isothiocyanate moiety of MS-ITC plays an important role for antiplatelet and anticancer activities because of its highly reactivity with sulfhydryl (-SH) groups in biomolecules (GSH, cysteine residue in a certain protein, etc.).

Developing a new model for non-insulin dependent diabetes mellitus (NIDDM) by using the Philippine wild mouse, Mus musculus castaneus.

The Philippine wild-caught castaneus mouse (Mus musculus castaneus) and laboratory mouse (C57BL/6J: B6) were used to develop a new non-insulin dependent diabetes mellitus (NIDDM) model. Offspring from the cross between a wild male and B6 female were backcrossed to the sire. One male which exhibited highest fasting hyperglycemia (190 mg/dl) among eighty-seven backcross offspring was selected at 10 weeks of age, and crossed with a B6 female to comprise the fundamental stock (F0). Thereafter, full-sib mating was performed to develop a new inbred strain named CBD (Castaneus-B6 diabetic) mouse. Mice with relatively higher fasting hyperglycemia among F0 and F1 generations were selected for breeding. From the F2 generation, mice were defined as diabetic when blood glucose levels exceeded 200 mg/dl at 120 min in intraperitoneal glucose tolerance test (IPGTT) at 10 weeks of age, and have been selectively bred. The incidence of diabetic males from the F3-F6 generation fluctuated 45-75% at 10 weeks of age and 59-72% at 20 weeks of age. Diabetic males had about two-fold higher fasting glucose and insulin levels than B6 males. Glucose-stimulated insulin secretion was impaired in diabetic CBD mice compared to B6 males at 20 weeks. Moreover, diabetic mice had slight obesity compared to B6 mice. These facts indicated that diabetic features of CBD mice resemble NIDDM in humans. The CBD strain, characterized by high incidence and early onset of diabetes with mild obesity would be of value as a new NIDDM model. The method, utilizing wild castaneus mouse of different origin from laboratory mice, maybe useful in the development of other animal models.

Characterization of hyperinsulinemic recombinant inbred (RI) strains (SMXA-5 and SMXA-9) derived from normoinsulinemic SM/J and A/J mice.

We discovered two mouse strains (SMXA-5 and SMXA-9) with hyperinsulinemia among the substrains and progenitor strains (SM/J and A/J) of the SMXA recombinant inbred (RI) strains, and characterized the two strains at 20 weeks of age. SMXA-5 (mean +/- S.E.M: 9.6 +/- 1.7 ng/ml) and SMXA-9 (7.7 +/- 1.3 ng/ml) males had higher serum immunoreactive insulin levels than SM/J (1.4 +/- 0.3 ng/ml) and A/J (1.1 +/- 0.1 ng/ml) males in the nonfasting condition. The hypoglycemic response to insulin at 30 min after injection was significantly less in SMXA-5 males than in SM/J mice. Glucose tolerance test revealed that the incidence of impaired glucose tolerant males was 58% (11/19) in SMXA-5 and 42% (10/24) in SMXA-9 strains, but none in SM/J and A/J strains. SMXA-5 (209 +/- 29 mg/dl) and SMXA-9 (235 +/- 31 mg/dl) had higher serum triglyceride levels than SM/J (126 +/- 14 mg/dl) and A/J (89 +/- 5 mg/dl) males in the nonfasting condition. Histologic examination revealed enlarged islets in the pancreas of hyperinsulinemic SMXA-5 male mice. Moreover, SMXA-5 and SMXA-9 mice exhibited mild obesity. SMXA-5 and SMXA-9 males were therefore characterized by hyperinsulinemia, impaired glucose tolerance, hypertriglyceridemia and mild obesity which resembled some of the phenotypes of human Syndrome X, although both progenitor strains were normal so far as we examined. Since the RI strains are a powerful tool to facilitate polygenic-trait analysis, SMXA-5 and SMXA-9 mice will be useful materials to investigate the genetic basis of complex diseases, and are possible new metabolic models in relation to hyperinsulinemia.

Blood and liver lipid concentrations in EDS shrews exhibiting spontaneous non-insulin dependent diabetes mellitus (NIDDM).

The EDS (early-onset diabetes in suncus) colony was developed as a new laboratory colony of the musk shrew and is characterized by a high incidence of early-onset spontaneous non-insulin dependent diabetes mellitus (NIDDM). We examined blood lipid (triglyceride [TG], total cholesterol [TC], phospholipid [PL], free fatty acid [FFA]) and liver lipid (TG, TC, PL) concentrations to investigate the features of lipid metabolism in these animals. All lipid concentrations examined both in blood and liver of the diabetic shrews had a tendency toward higher values than those in non-diabetic shrews. The PL concentration was the only parameter that barely showed a significant difference. Values for all blood lipid concentrations in diabetic shrews at 7-9 months tended to be higher than those of 2-month-old diabetic shrews, although the difference was not significant. These findings indicate that diabetic EDS shrews exhibit a much milder defect of lipid metabolism induced by NIDDM than other rodent models.

Distribution of body weight, blood insulin and lipid levels in the SMXA recombinant inbred strains and the QTL analysis.

In the SMXA recombinant inbred (RI) strains, we measured body weight, blood insulin and lipid (triglyceride, total cholesterol and phospholipid) levels in each strain. In the five traits, mean values of substrains varied remarkably and showed a continuous spectrum of distribution, suggesting control by multiple genes at distinct loci for each trait. We also screened for quantitative trait loci (QTLs) involved in the five traits. Suggestive QTLs for body weight (Chromosomes 1 and 6), insulin (Chromosomes 1, 3, 10 and 17), triglyceride (Chromosomes 4 and 11) and phospholipid (Chromosome 18) levels were detected. The SMXA RI strains are unique tools for analyzing genetic factors that influence body weight, blood insulin and lipids levels.

Quantitative trait loci for body weight in the intercross between SM/J and A/J mice.

We performed a genome-wide quantitative trait locus (QTL) analysis of body weight at 10 weeks of age in a population of 321 intercross offspring from SM/J and A/J mice, progenitor strains of SMXA recombinant inbred strains. Interval mapping revealed two significant QTLs, Bwq3 (body weight QTL3) and Bwq4, on Chromosomes (Chrs) 8 and 18 respectively, and five suggestive QTLs on Chrs 2, 6, 7, 15 and 19. Bwq3 and Bwq4 explained 6% of the phenotypic variance. The SM/J alleles at both QTLs increased body weight, though the SM/J mouse was smaller than the A/J mouse. On the other hand, four of the five suggestive QTLs detected had male-specific effects on body weight and the remainder was female-specific. These suggestive QTLs explained 5-6% of the phenotypic variance and all the SM/J alleles decreased body weight.

Effect of an amino acid imbalance on intestinal sucrase and leucine aminopeptidase activities in rats.

In order to investigate the relationship between dietary amino acids and protein, as well as the activities of intestinal sucrase and leucine aminopeptidase in rats, the effects of an amino acid imbalance on these enzyme activities were studied. The amino acid imbalance was created by adding 8% of an indispensable amino acid mixture lacking threonine to a 6% casein diet supplemented with 0.3% methionine. The food intake and growth of rats fed the imbalanced diet ad libitum were depressed, and the segmental weights of the small intestine and its sucrase activity were clearly lower than those of rats fed the basal diet. The effect of the imbalanced diet under pair-feeding condition on the sucrase activity was similar to that under an ad libitum feeding condition. The food intake and segmental sucrase activity, that is, sucrase activity per length of the small intestine, of rats injected with cortisol (1 mg/day) and fed the imbalanced diet were not depressed, although administration of insulin (1.5 U/day) had no effect on the food intake or segmental sucrase activity. Force-feeding stimulated growth of rats receiving the imbalanced diet, as well as increasing their segmental sucrase activities. The effects of these different conditions on the leucine aminopeptidase activity of rats receiving the imbalanced diet were obscure. These results suggest that changes in segmental sucrase activity might be mediated by stimulating factors in food intake affected by the composition of ingested amino acids and protein together with sucrose in the gastrointestinal lumen.

Effect of several xenobiotics on the activities of enzymes affecting ascorbic acid synthesis in rats.

The dietary addition of several xenobiotics, such as PCB, DDT, aminopyrine, chloretone, BHT and BHA, caused significant increases in the ascorbic acid in urine and liver of rats. The administration of all types of xenobiotics used in the present experiments increased the activity of hepatic UDP-glucose dehydrogenase (1.3-2.8-fold), and the administration of PCB, DDT, BHT or BHA significantly increased the activity of hepatic UDP-glucuronyl transferase (2.2-13.1-fold). The activity of beta-glucuronidase was slightly increased with feeding of PCB, DDT, chloretone or aminopyrine. However, the activity of hepatic UDP-glucuronic acid pyrophosphatase, the conversion of D-glucuronic acid or D-glucuronolactone into L-ascorbic acid and the activity of hepatic L-gulonolactone oxidase did not increase with the administration of PCB or DDT. It is suggested that the increases in the activities of UDP-glucose dehydrogenase and UDP-glucuronyl transferase would have a major role in the stimulation of ascorbic acid synthesis in xenobiotic treated rats.