Effects of maturational age of recipient oocytes and activation conditions on the development of porcine fetal fibroblast nuclear transfer embryos.

This study was conducted to evaluate the nuclear remodeling patterns and the developmental potential of porcine fetal fibroblast nuclear transfer embryos (NTs) following the maturational age of recipient oocytes and activation conditions. Donor cells were transferred into the enucleated oocytes that were matured for 36 or 44h. Electrofused embryos were cultured in PZM-3 for 6 days without activation treatment (EF group). Some of these embryos were additionally activated by electric stimulus (ES; EF+ES group) or a combination of ES and DMAP (EF+ES+D group) before culture. The reconstituted embryos were fixed 2.5h after fusion to evaluate the nuclear remodeling patterns. The nuclear remodeling pattern of NTs reconstituted with 44 h-matured recipients showed a tendency to form a pronucleus-like structure, while that of NTs reconstituted with 36 h-matured recipients showed a tendency to undergo a premature chromosome condensation (PCC) and form one set of chromatin clump. In EF+ES+D group, blastocyst development was significantly increased regardless of maturational age of recipient oocytes (P<0.05). The result indicates that additional activation treatment is necessary to induce the activation of embryos reconstituted with 36 h-matured recipients, and treatment with the combination of electrical stimuli and DMAP could enhance the blastocyst formation rate of porcine NTs reconstituted with both 36 h- and 44 h-matured recipient oocytes.

Probabilistic dietary exposure to ethyl carbamate from fermented foods and alcoholic beverages in the Korean population.

The occurrence of ethyl carbamate was investigated in fermented foods and alcoholic beverages of the Korean total diet study. The concentrations of ethyl carbamate ranged from not detected to 166.5 µg kg-1. Dietary exposure to ethyl carbamate was estimated by the probabilistic method. Estimated intakes of ethyl carbamate from foods and alcoholic beverages were 4.12 ng kg-1 body weight (bw) per day for average consumers and 12.37 ng kg-1 bw/day for 95th percentile high consumers. The major foods contributing to ethyl carbamate exposure were soy sauce (63%), followed by maesilju (plum liqueur, 30%), whisky (5%), and bokbunjaju (black raspberry wine, 2%). On the basis of the benchmark dose lower confidence limit 10% (BMDL10) of 0.3 mg kg-1 bw/day, margins of exposure were 128,000 for mean exposure and 40,000 for 95th percentile exposure. This indicates that the exposure of the Korean general population for ethyl carbamate is of low concern. However, careful vigilance should be continued for high consumers of fermented foods and alcoholic beverages.

The impact of obesity on febrile urinary tract infection and renal scarring in children with vesicoureteral reflux.

INTRODUCTION: It has become clear that obesity is associated with a variety of infectious diseases, including urinary tract infection (UTI) and renal scarring. OBJECTIVE: The aim of this study was to evaluate the association between obesity and the degree of febrile UTI (fUTI) and renal scarring in children with vesicoureteral reflux (VUR), and to stratify the results into obesity subcategories. STUDY DESIGN: A total of 186 patients were diagnosed with VUR between January 2002 and December 2008. This study retrospectively reviewed the medical records of 72 children with primary VUR who had recurrent fUTI (more than twice). Overweight or obese status of the patients aged <2 years was defined using weight-for-length (WFL) measurements. For 2-5 year old children, body mass index (BMI) percentile-for-age was used. They were divided into three groups as follows; standard (<85%), overweight (85-95%), and obese (≥95%). The following clinical variables were compared: age at diagnosis of primary VUR (months), sex, VUR grade, hydronephrosis grade, presence of renal scarring, surgical treatment, and degree of inflammation during fUTI. RESULTS: In the overweight and obese groups, VUR was diagnosed at a young age (P = 0.05), the degree of renal scarring was more severe (P = 0.006), and serum white blood cell count, C-reactive protein, and erythrocyte sedimentation rate (ESR) levels were significantly higher (P < 0.001, P < 0.001, and P < 0.001, respectively). Abnormal focal dimercaptosuccinic acid (DMSA) defects were present in 25 of the 72 children (35%). Cortical defects occurred more frequently in children with obesity, and they were associated with a higher grade of reflux and serum ESR levels (P = 0.007, P = 0.042, and P = 0.021, respectively). Among these risk factors, high-grade VUR (OR = 9.93, 95% CI = 1.13-86.71), and being overweight and obese (OR = 5.26, 95% CI = 1.75-15.82) were associated with increased renal scarring. However, ESR was not associated with renal scarring (OR = 1.01, 95% CI = 0.95-1.07). DISCUSSION: The relationships between obesity and UTI are controversial. Some studies have shown positive results; however, other studies have shown opposite results. The main limitations of this study were the retrospective data collection via electronic medical records, and the small number of subjects. CONCLUSIONS: This study showed that obesity in patients with VUR has an effect on fUTI and renal scar formation. If the patients with VUR have obesity, close follow-up should be performed, and VUR patients should be started on a weight-loss program, which could reduce the number of patients with chronic kidney disease in the future.

Primary structure of bacteriophage M2 DNA polymerase: conserved segments within protein-priming DNA polymerases and DNA polymerase I of Escherichia coli.

Bacteriophage M2 encodes its own DNA polymerase which catalyses the formation of a primer protein-5'dAMP initiation complex for DNA replication. To understand the relation of structure to function of this 'protein-priming DNA polymerase', we have determined the nucleotide sequence of the M2 DNA polymerase-encoding gene (gene G). The deduced 572-amino acid sequence of M2 DNA polymerase shows 82.3% overall homology to that of phi 29 DNA polymerase. A homology search with the mutation data matrix revealed that six segments (A-F, from the N terminus) of M2 and phi 29 DNA polymerases are homologous with the sequence of Escherichia coli DNA polymerase I (PolI). Segments D and F coincide with the conserved segments of many other DNA polymerases. Therefore, M2 and phi 29 DNA polymerases have structural features, at least in the conserved segments, similar to those of PolI and other DNA polymerases. Based on the homology with PolI and the location of the mutations for aphidicolin resistance and nucleoside analog resistance of M2, phi 29 and herpes simplex virus type-1 DNA polymerases, we propose that segments A-D of the M2 and phi 29 DNA polymerases constitute a structure which forms the cleft for holding template DNA and that segment D is a region for interacting with dNTP.

Ultraviolet light-induced reductions in plasma carotenoid levels.

The effects of ultraviolet (UV) irradiation on plasma levels of carotenoids and vitamin A in human subjects were investigated in two crossover trials. UV exposures were given on 11 r 12 days of a 2-wk period. The 12 female and 12 male subjects received mean cumulative UV-A (320-400 nm) doses of 17.8 +/- 1.9 J/cm2 and 21.0 +/- 3.3 J/cm2 to the anterior and posterior sides of the body, respectively. UV-B (280-320 nm) doses were equivalent to 10% of UV-A doses given. Significant reductions in plasma total carotenoid levels were observed in both female (p less than 0.004) and male (p less than 0.05) subjects after repeated irradiation. There was no significant effect on plasma vitamin A levels. It was concluded that UV treatment can reduce plasma carotenoid levels in vivo.

Increased hepatic retinal dehydrogenase activity after phenobarbital and ethanol administration.

Cytosolic retinal dehydrogenase (EC 1.2.1.36, retinal: NAD+ oxidoreductase) activity was measured by assessing the conversion of retinal to retinoic acid by HPLC. In vitro, acetaldehyde, chloral hydrate and disulfiram were found to be inhibitors, whereas 95% of the activity remained in the presence of cyanide or in the absence of oxygen. In rats, retinal dehydrogenase activity prevailed over that of retinal oxidase. By contrast, in deermice, 80% of retinal oxidation was due to the oxidase rather than the retinal dehydrogenase activity in a normal strain (ADH+) as well as in one lacking alcohol dehydrogenase (ADH-). In ADH- deermice, retinal oxidase activity was greater than in ADH+ animals. In vivo, in the rat, chronic ethanol administration resulted in a significant increase of the dehydrogenase activity in the liver, but not in other tissues. After phenobarbital administration, hepatic retinal dehydrogenase activity was increased 8-fold, but no extrahepatic induction was observed. Conversely, feeding rats with a diet devoid of the precursor for the substrate (retinal) by replacing retinyl acetate with an equivalent amount of retinoic acid resulted in decreased retinal dehydrogenase activity. Under conditions in which retinal dehydrogenase activity is rate-limiting for the metabolism of retinal to retinoic acid, its induction after phenobarbital or ethanol administration may contribute to hepatic vitamin A depletion.

Multicenter study of the treatment of erectile dysfunction with transurethral alprostadil (MUSE) in Korea.

A Korean multicenter study was conducted to assess the effectiveness of transurethral alprostadil with MUSE in 334 subjects with chronic erectile dysfunction (ED) who were enrolled in 21 clinical centers. Patients with psychogenic impotence comprised about 30% of subjects. Intraurethral alprostadil was titrated in a stepwise fashion in the clinics from 250 to 500 or 1000 mcg based on erectile response and tolerability. The erectile responses were evaluated using an erection assessment scale (score of 1-5). The dose that produced a maximal penile response of score 5 (full rigid erection) or 4 (full tumescence, partial rigidity) was selected for home treatment. Patients who showed partial erection (score of 3) with 1000 mcg were also included in the home-treatment group. In-clinic phase: 198 men (59.3%) had maximal penile responses of score 4 or 5. The rate of maximal responses was not related to patient age, etiology or duration of the ED. A total of 228 (68.3%) men progressed to home treatment. The overall level of comfort of the transurethral alprostadil was rated as uncomfortable or very uncomfortable in 12%. Home phase: During the two-month period of home treatment, 178 (78.1%) men had successful sexual intercourse at least once, and 78.2% of administrations (1976) resulted in successful intercourse. The main causes of drop-out were insufficient erectile response in 27 men (11.8%), adverse reactions (mostly penile or urethral pain) in 7 (3.1%) or both in 7 (3.1%). In conclusion, transurethral alprostadil could be a suitable treatment option for patients with ED regardless of age and etiology of ED. Efficacy in an Asian population (Korea) is comparable to that reported previously in Caucasians.

Very low dose danazol in idiopathic thrombocytopenic purpura and its role as an immune modulator.

Danazol, an attenuated androgen, has been used successfully at its conventional dose (400-800 mg/day) in the treatment of idiopathic thrombocytopenic purpura (ITP). To minimize side effects, the authors tried a very low dose (50 mg/day) regimen which has not been used in any other disease and observed its efficacy in ITP. Fifteen patients were given this dosage of danazol. Its effects on T-cell subsets, B cells, and blastogenic response to pokeweed mitogen (PWM) and staphylococcus aureus (Staph A) were studied before and during therapy. The percentage of CD3 and the percentage and numbers of CD4 were significantly increased during therapy. Responses to PWM, a T-cell dependent B cell mitogen, were also significantly elevated during therapy. However, no change in the percentage of B (CD19) lymphocytes and response to Staph A, a polyclonal B cell mitogen, were noted. There were seven excellent-good and eight fair-poor responses in platelet counts. The excellent-good responders were found to have a more stable CD4 subset between before and during therapy compared to the fair-poor responders (p less than 0.05, Fisher's exact test). Very low dose danazol regimen, therefore, produced a significant increase in the CD4 without affecting the B cells. However, the excellent-good responder patients showed no significant increase in the CD4 lymphocytes.

Effect of a fertilization-promoting peptide on the fertilizing ability and glycosidase activity in vitro of frozen-thawed spermatozoa in the pig.

This study has evaluated the effect of fertilization-promoting peptide (FPP) on the fertilizing ability and glycosidase activity in vitro of frozen-thawed boar spermatozoa. Use of chlortetracycline (CTC) fluorescence analysis, as well as various glycosidase analyses and the oocyte penetration test showed that FPP can promote the fertilizing ability and glycosidase activity of frozen-thawed spermatozoa in vitro. There were significantly (P < 0.05) more acrosome-reacted and penetrated in medium with 100 nM FPP than with 0, 50, 200 or 400 nM. The beta-N-acetylglucosaminidase (beta-GlcNAcase) activity was at least two-fold higher than other glycosidase regardless of FPP concentrations. In the same glycosidase, there were no differences in medium with different concentrations of FPP. The percentages of spermatozoa that reached acrosome reaction were affected by different periods (0, 1, 2, 3 or 4 h) of spermatozoa preincubation and were higher in medium with than without FPP. Penetration rates were decreased with preincubation periods of spermatozoa when oocytes were inseminated with spermatozoa preincubated in medium with and without FPP for the different periods. These rates were higher in spermatozoa preincubated with that than without FPP and had a tendency to increase as time of culture periods when the sperm-oocyte were cultured for 4, 8, 12, 16, 20 or 24 h. The activities of alpha-fucosidase, alpha-mannosidase, beta-galactosidase and beta-GlcNAcase were higher in medium with that than without FPP regardless of periods of sperm preincubation and sperm-oocyte culture. These results suggest that FPP may have a positive role in promoting sperm function and glycosidase activity in the pig.

Production of tumor necrosis factor by intravesical administration of bacillus Calmette Guérin in patients with superficial bladder cancer.

Although an immune response to bacillus Calmette Guérin (BCG) has often been associated with antitumor activity, the action mechanism(s) of intravesical BCG therapy for prophylaxis and treatment of superficial bladder cancer is not clearly understood. In an attempt to evaluate the roles of tumor necrosis factor (TNF)-alpha and lymphotoxin (LT) in the antitumor activity, TNF-alpha productivities by peripheral blood monocytes, serum levels of TNF-alpha, and LT productivities by peripheral blood lymphocytes were studied in superficial bladder cancer patients after six intravesical administrations of BCG. TNF-alpha productivities by peritoneal macrophages of guinea pigs were also studied after six intravesical administrations of BCG. The maximum TNF-alpha productivities by peripheral blood monocytes of superficial bladder cancer patients were seen after the fourth week of administration of BCG, and the serum TNF-alpha levels were also slightly increased after intravesical BCG administration in the superficial bladder cancer patients. LT productivities by peripheral blood lymphocytes of superficial bladder cancer patients were significantly enhanced and the maximum LT productivity was also seen after the third or fifth BCG administration. TNF-alpha productivities by peritoneal macrophages of guinea pigs were significantly enhanced and the maximum TNF-alpha productivity was seen after the second or third BCG administration. Our data might suggest that six consecutive intravesical BCG administrations could induce the increased productions of TNF-alpha and LT, which might play an important role in the antitumor activity in superficial bladder cancer.

Maturation, fertilization and development of bovine oocytes in vitro using TCM199 and a simple defined medium with co-culture.

Bovine oocytes obtained from ovarian follicles (2 to 5 mm in diameter) from slaughtered cattle were cultured in TCM199 with 10% heat-inactivated estrous cow serum (ECS) for 24 to 25 h at 39 degrees C under 5% CO(2) in air. The 10% ECS was selected on the basis of preliminary studies in which in vitro fertilization rates of oocytes with 10, 15 and 20% ECS in the medium were 46, 30 and 31%, respectively (P<0.05). Of 120 oocytes cultured for 24 to 25 h, 63% were classified as being in Metaphase II. The rate of oocytes matured in vitro was 55% (69 125 ), the proportion of penetrated oocytes which contained male and female pronuclei was 94% (65 69 ), and the incidence of polyspermy was very low (0 to 9%). Of 122 oocytes fertilized in vitro and cultured in TCM199 medium with 10% fetal bovine serum for 7 d, 53% were cleaved, but only 2% developed beyond the 16-cell block. However, in simple semi-defined Chatot-Ziomek-Bavister medium co-cultured with bovine oviduct epithelial cells (BOEC), 75% of 138 oocytes cleaved, and 38% of those which cleaved developed into morulae or blastocysts. The results of this study indicate that co-culture with BOEC exerted a pronounced beneficial effect on development of in vitro fertilized bovine oocytes through the 16-cell block. The medium required in the co-culture system was simple and semi-defined.

Current concepts of cell-cycle regulation and its relationship to oocyte maturation, fertilization and embryo development.

Genetic and biochemical approaches have contributed to an explosion of literature on cell-cycle control. Regulation of the cell-cycle is controlled by a series of kinases and phosphatases. Key control points are during the G(1)-S and G(2)-M transitions. During both transitions, cyclins interact with a specific kinase to allow a cell to pass through that phase. The meiotic maturation of oocytes, fertilization and embryo development are all events influenced by cell-cycle regulation. Understanding cell-cycle control should provide new ways for gamete and embryo biologists to approach culture and development problems.

Effect of superoxide dismutase(SOD) on pronucleus formation of porcine oocytes fertilized in vitro.

This study was undertaken to evaluate the effects of superoxide dismutase (SOD) on pronucleus formation in porcine oocytes fertilized in vitro by frozen-thawed spermatozoa. No differences were found in penetration rates when SOD was added to maturation or fertilization medium at any level tested in first and second experiments. Pronucleus formation rates were higher (P < 0.05) when SOD at 10 and 100 units was added to the maturation medium (46 and 53%, respectively) compared with the controls (26%). On the other hand, when the fertilization medium was supplemented with SOD at different concentrations (1, 10 and 100 units/ml), pronucleus formation rates (55, 52 and 50%) were significantly higher (P < 0.05) than in the control group. In third experiment, the oocytes were cultured in medium with (1 unit/ml) or without SOD for 8, 16, 24 and 32 h after insemination. The penetration rates had a tendency to increase as time of sperm-oocyte culture was prolonged. No significant differences, however, were observed in penetration rates between groups with and without SOD. On the other hand, the pronucleus formation rates were higher in medium with than without SOD at 8 (7 vs 0%), 16 (14 vs 3%), 24 (48 vs 16%; P < 0.01) and 32 h (49 vs 22%; P < 0.05). These findings demonstrate the advantage of culture with SOD on pronucleus formation in porcine oocytes penetrated by spermatozoa. However, SOD does not affect penetration rates and polyspermy.

The relationship between family and child weight status by household structure in South Korea: 2007-2010.

OBJECTIVE: Parental obesity has been identified as a predominant risk factor for childhood overweight and obesity. We investigated the relationship between parent and child obesity in South Korea, particularly linked with varying family structures. SUBJECTS AND METHODS: Data for households with children aged 2-18 years were taken from the pooled data of the Korea National Health and Nutrition Examination Survey (KNHANES) 2007-2010 conducted by the Korea Centers for Disease Control and Prevention (KCDC). The sample consisted of 17 453 individuals (7879 children and 9574 adults) from 5048 households with children for this study. Children's overweight and obesity prevalence was compared using both International Obesity Taskforce (IOTF) and KCDC cutoff points according to parental weight status and household structure. Logistic regression analysis was used. RESULTS: Significantly greater odds of overweight and obesity existed among children living with both parents (odds ratio (OR)=3.5, 95% confidence interval (CI): 2.71, 4.65) or one parent (mother: OR=1.6, 95% CI: 1.22, 2.12; father: OR=1.7, 95% CI: 1.37, 1.99). The adjusted ORs for overweight and obesity among children living with overweight mother only or overweight grandparent only were approximately double that of children living with normal-weight mother (OR=2.2, 95% CI: 1.22-3.82) or normal-weight grandparent (OR=2.1, 95% CI: 1.06-4.05). CONCLUSION: Children living with overweight parent(s) or grandparent(s) were positively correlated with the risk for childhood overweight and obesity. Socioeconomic status did not affect the observed relationships in this population, whereas the role of genetic, dietary and activity patterns requires further exploration.

Overall and abdominal adiposity and hypertriglyceridemia among Korean adults: the Korea National Health and Nutrition Examination Survey 2007-2008.

BACKGROUND/OBJECTIVES: Obesity is associated with increased triglyceride levels. We examined whether overall obesity (body mass index (BMI)) and abdominal obesity (waist circumference (WC)) are independently associated with hypertriglyceridemia among the Korean population. SUBJECTS/METHODS: A national sample of 5036 Koreans aged 19-64 was examined with cross-sectional surveys, the Korea National Health and Nutrition Examination Survey, in 2007 and 2008. BMI, WC and other lifestyle information were assessed. RESULTS: We documented 1344 cases (26.7%) of hypertriglyceridemia (fasting triglycerides of >150 mg/dl). Both BMI and WC were each independently associated with hypertriglyceridemia. Multivariate odds ratios (ORs) of increasing categories of BMI (<18.5, 18.5≤ - <23, 23≤ - <25, 25≤ - <28, ≥28 kg/m²), were 0.49, 1.00 (reference), 1.26, 1.63 and 1.84, respectively (P=0.0007) adjusting for WC. There was a positive association between WC and hypertriglyceridemia across increasing quintiles of WC (multivariate-adjusted ORs: 1.00 (reference), 1.54, 2.54, 2.21 and 2.36; P<0.0001), adjusting for BMI. WC was positively related to hypertriglyceridemia in both gender. However, only women's BMI was independently associated with hypertriglyceridemia after adjusting for WC. The joint relation between BMI and WC and hypertriglyceridemia showed that within each BMI category, higher WC predicted a greater prevalence of hypertriglyceridemia and vice versa. The receiver operating characteristic curves indicated that BMI (0.69) and WC (0.72) were similar in predicting hypertriglyceridemia. CONCLUSIONS: Both BMI and WC were strongly independently associated with hypertriglyceridemia among the population. Both measurements should be considered for use in assessing health risk at clinical settings and epidemiologic research among Asian population.

Sexuality and the management of BPH with alfuzosin (SAMBA) trial.

The sexuality and the management of benign prostatic hyperplasia (BPH) with alfuzosin (SAMBA) trial evaluated the effect of alfuzosin on sexual function in men treated for BPH using two sexual function scales: male sexual health questionnaire (MSHQ) and international index of erectile function (IIEF-15). A total of 148 patients with BPH were treated with alfuzosin for 24 weeks. The patients were followed at baseline, 4, 12 and 24 weeks after medication with alfuzosin. MSHQ was collected at every visit, whereas Q(max), IPSS and IIEF-15 were checked at baseline and end point. At the end point, Q(max) (+4.7 ml s(-1), P<0.01) and IPSS (-5.3, P<0.01) had improved significantly. Alfuzosin also significantly improved the total MSHQ (19.2%, 79.1-94.3, P<0.01) and the MSHQ ejaculatory scores (26.0%, 22.3-28.1, P=<0.01) versus baseline. Alfuzosin for the treatment of patients with BPH is effective in improving sexual function, as well as lower urinary tract symptoms (LUTSs) and quality of life, and is well tolerated.

Development of riboflavin deficiency in alcohol-fed hamsters.

Riboflavin deficiency may be induced by dietary restriction or by drugs. High incidence of rifoflavin deficiency in alcoholics might be due to diet, to the toxic effect of alcohol, or to an interaction of these variables. Aims of this study were to investigate the effects of alcohol on the riboflavin status of Syrian hamsters fed three different levels of riboflavin in a liquid diet. Male Syrian outbred hamsters of 5 weeks of age, acclimated to liquid diets, were randomly assigned to groups that received alcohol-containing diets (AR0, AR1, AR2) or nonalcohol-containing diets (OR0, OR1, OR2) where R1 = 0.5 microgram riboflavin/kcal added and R2 = 1.5 microgram riboflavin added/kcal. No alcohol groups were pair-fed to the alcohol groups. Riboflavin status was monitored by repeated erythrocyte glutathione reductase assays. Animals were sacrificed at 13 weeks of age and liver flavins were determined. Riboflavin depletion occurred during the first 2 weeks of the study and this was followed by a 4-week period of relative improvementin riboflavin status. Thereafter riboflavin depletion continued in all groups but most severely in the alcohol group as measured by erythrocyte glutathione reductase assays. Total liver flavins were lowest in the alcohol-fed, riboflavin-restricted group, indicating that chronic alcohol feeding can induce riboflavin deficiency when intake of the vitamin is marginal.

Increased vitamin A in esophagus and lungs after moderate ethanol consumption.

Moderate ethanol consumption, at the level of 18% of total energy as part of a liquid diet, was found to result in a significant increase of total vitamin A content in the esophageal mucosa in rats fed normal-zinc-containing or zinc-supplemented diets. There was also an increase in total vitamin A content in the lungs after ethanol consumption, but the change was significant only in the zinc-supplemented group. In the liver, retinyl palmitate plus oleate decreased after ethanol, whereas free retinol, retinyl stearate, and linoleate increased. Ethanol consumption resulted in a modest decrease in hepatic zinc content when expressed per gram of liver, but not per total liver (per 100 gram of body weight). Although chronic ethanol consumption at the level of 18% of total energy did not affect total hepatic vitamin A, there was still a significant increase of vitamin A content in esophagus and lungs.

Role of vitamin A degradation in the control of hepatic levels in the rat.

The relationship between excess vitamin A intake and accumulation in various tissues, including the liver, was studied in rats fed for 45 d four levels of vitamin A: 1, 6, 30 and 100 IU/kcal. As vitamin A intake increased, progressively smaller fractions of the administered vitamin A were recovered in tissue. The decrease in fractional recovery in the tissues examined was calculated from the differences between intake, tissue level and excretion, and was found to increase after administration of high vitamin A diets. This could be explained, at least in part, on the basis of an enhanced rate of vitamin A degradation as a function of the increased concentration of retinol in the liver. At high tissue retinol concentrations, calculated rates of retinol metabolism via the hepatic cytosolic retinol dehydrogenase (EC 1.1.1.1) and the recently discovered microsomal retinol dehydrogenase and oxidase vastly exceeded the decrease in fractional recovery of vitamin A accumulation in the tissues. This calculated rise in metabolic rate was verified by a corresponding increase in urinary polar metabolites derived from labeled retinol. Thus, accelerated catabolism as a function of increased hepatic vitamin A concentration may provide a homeostatic mechanism which offsets in part excessive vitamin A accumulation.

Retinol forms retinoic acid via retinal.

Hepatic cytosol from normal deermice having cytosolic alcohol dehydrogenase (ADH+) also displays retinol dehydrogenase activity and converts retinol to retinoic acid, whereas cytosol from ADH- deermice lacks these enzyme activities and does not produce retinoic acid. Furthermore, microsomes from either strain do not convert retinol to retinoic acid. However, when cytosol from ADH- animals is added to the microsomes, retinoic acid is produced. The obligatory role of retinal as an intermediary step in retinoic acid formation is further shown by isotopic dilution of retinoic acid formed from labeled retinol upon addition of unlabeled retinal. Microsomal retinol dehydrogenase also catalyzes the reduction of retinal to retinol, thereby explaining the decrease in retinoic acid production from retinol in liver cytosol of ADH+ deermice when microsomes are added. Thus, the results of this study indicate that retinal is an obligatory intermediate in the hepatic production of retinoic acid from retinol and that cytosolic and microsomal retinol dehydrogenases play a key role in this process.