Α-glycerophosphate Dehydrogenase Activity Research Articles

Effects of clofibrate on mitochondrial function

The effects of ethyl and sodium clofibrate on mitochondrial function were studied. Both compounds exerted similar effects, the ethyl derivative being more potent. State 3 respiration was inhibited; the order of inhibitory effectiveness was NAD +-dependent substrates > succinate > ascorbate. State 4 NAD +-linked oxidation was not significantly affected, but state 4 oxidations of succinate and ascorbate were stimulated by ethyl clofibrate. Energy production was inhibited, as evidenced by the decrease in the respiratory control ratio, the P/O ratio and the ATP- 32P exchange reaction. Energy utilization, assessed by substrate or ATP-supported energy-linked Ca 2+ uptake, was also inhibited. By contrast, energy-independent Ca 2+ uptake was not affected. Clofibrate interfered with the integrity of the mitochondrial membranes, since it stimulated ATPase activity and increased the normally low permeability of intact mitochondria toward NADH. The transfer of reducing equivalents into the mitochondria, catalyzed by the α-glycerophosphate, fatty acid or malate-aspartate shuttles, was inhibited by sodium clofibrate. These results may explain our previous finding that the reconstituted a-glycerophosphate shuttle was not stimulated in rats fed clofibrate, despite an increase in the activity of mitochondrial α-glycerophosphate dehydrogenase.

Enzymes of Carbohydrate Metabolism in Normal Human Sebaceous Glands

Glucose, glycogen, and ATP concentrations were measured in the peripheral and central layers of the sebaceous glands as well as in the epidermis. Both carbohydrates exhibited a decreasing gradient of concentration from the periphery to the center of the glands. No differential distribution of ATP content was found in the sebaceous glands. The periphery of the glands contained 8 m moles glucose, 22 m moles glycogen, and 10 m moles ATP per kg dry weight tissue. The glucose and ATP concentrations were comparable to those in epidermis, whereas on the basis of lipid-free dry weight the amount of glycogen at the periphery was 6.3 times that of epidermis. The total NADP concentration in sebaceous glands was 0.5 m moles/kg dry weight, 78 percent of which was in the reduced form; the total NAD concentration was 1.4 m moles/kg dry weight, 34 percent of which was in the reduced state. Sebaceous glands contained 3 times more NADP nucleotides than epidermis. The ratios of the NAD nucleotides to NADP nucleotides were 3: 1 in the sebaceous glands and 8: 1 in the epidermis. Of the 29 enzymes assayed, the most prominent in the sebaceous glands were α-glycerophosphate dehydrogenase, malic enzyme, alanine amino-transferase, glucose-6-phosphate dehydrogenase, and phosphorylase. Enzyme analyses also demonstrated increased contributions of the pentose phosphate pathway and tricarboxylic acid cycle, a significant role for glycogen metabolism and active glycolysis. The high activities of α-glycerophosphate dehydrogenase and triosephosphate isomerase suggest that triosephosphate is being shifted into α-glycerophosphate for the acylglycerol formation. The high aminotransferase activities suggested an important contribution of amino acid metabolism to the sebaceous glands. The conspicuously high activity of alanine aminotrans-ferase indicates a tissue potential to convert amino acids to pyruvate in sebaceous glands. High malic enzyme and malate dehydrogenase activities suggest a malate shunt, by means of which an ATP-driven transhydrogenation between NADP and cytoplasmic NADH occurs to produce NADPH. Isocitrate dehydrogenase was the most active among the NADP-dependent enzymes and appeared to participate in NADPH production in the sebaceous glands. Acid phosphatase activity was 5 to 7 times greated in the central portion than in the peripheral layers of the sebaceous glands. Three β-glycosidases were distributed more in the center than in the periphery of the glands. High acid phosphatase activity in the central portion of sebaceous glands may reflect its involvement in holocrine secretion.

Characterization of shuttle mechanisms for the transport of reducing equivalents into mitochondria

The malate-aspartate, fatty acid, and α-glycerophosphate shuttles for the transport of reducing equivalents into mitochondria were reconstituted, using isolated hepatic mitochondria and the extramitochondrial components of the shuttles. Clofibrate and thyroxin increased, while propylthiouracil treatment decreased, the activity of mitochondrial α-glycerophosphate dehydrogenase. Despite these changes, the activity of the reconstituted α-glycerophosphate shuttle was similar in mitochondria from control rats and those from rats treated with clofibrate and propylthiouracil. There was an increase in the activity of the shuttle using mitochondria from thyroxin-treated rats. Rotenone caused 60–90% inhibition of this shuttle, suggesting that rotenone-sensitive NADH dehydrogenase participates in the pathway of oxidation of extramitochondrial hydrogen. Palmitate, oleate, and octanoate were equally effective in reconstituting a cyclic fatty acid shuttle. The shuttle was inhibited by various compounds affecting mitochondrial metabolism, including oligomycin, dinitrophenol, cyanide, rotenone, atractyloside, and α-bromopalmitate. Carnitine and several dicarboxylic and tricarboxylic acids which stimulate fatty acid elongation, augmented fatty acid shuttle activity. The malate-aspartate shuttle was inhibited by cycloserine, amino-oxyacetic acid, and hydrazine, and stimulated by pyridoxal phosphate, at the same concentrations which affected the activities of cytoplasmic and mitochondrial glutamic oxalacetic transaminase. This shuttle was inhibited by uncouplers, antimycin, azide, cyanide, rotenone, amobarbital, oligomycin, and several inhibitors of anion transport including iodobenzylmalonate and avenaciolide. The reconstituted shuttle is sufficiently active to provide about 70–80% of the oxalacetate required for maximal rates of gluconeogenesis. Extrapolations based on the rates of mitochondrial oxidation of acetaldehyde and the activity of the microsomal ethanol oxidizing system suggest that any one of the shuttles could account for the rate of ethanol metabolism in vitro by the alcohol dehydrogenase pathway.

Metabolic alterations produced in the liver by chronic ethanol administration. Comparison between the effects produced by ethanol and by thyroid hormones

1. Liver slices from rats treated with thyroxine show an increased rate of O(2) consumption. The extra consumption, but not the basal respiration, can be abolished by ouabain. 2. Dinitrophenol is not effective in increasing the rate of O(2) consumption of liver slices from thyroxine-treated animals but its effectiveness can be recovered in the presence of ouabain. 3. (Na(+)+K(+))-stimulated adenosine triphosphatase activity of liver was increased by administration of thyroxine in vivo. No changes were found in total Mg(2+)-stimulated adenosine triphosphatase activity. 4. Mitochondrial alpha-glycerophosphate dehydrogenase and microsomal NADPH oxidase activity were increased by both thyroxine and chronic ethanol treatment. 5. Liver slices from animals chronically treated with ethanol synthesize urea at an increased rate. 6. Mitochondrial size (section area) is markedly increased in the liver of animals chronically treated with ethanol. 7. Acute administration of ethanol in doses of 4 and 6g/kg significantly increases the uptake of (131)I-labelled thyroxine by the liver. 8. Work reported here, along with results from other investigators, indicates marked similarities between the effects produced in the liver by chronic administration of ethanol and by thyroid hormones.

The Effect of Lipid Peroxide on the Lipid and Carbohydrate Metabolism in Rat Liver

Feeding tests were carried out on rats to clarify the mechanisms of fatty liver formation induced by autoxidized methyl linoleate. Lipid peroxides prepared by autoxidation of highly purified methyl linoleate were given orally to rats. Triglyceride and glycogen contents in liver were determined and enzyme activities including triglyceride synthetase and α-glycerophosphate dehydrogenase were also examined. The following results were obtained. 1. Triglyceride accumulation in rat liver fed autoxidized methyl linoleate was observed. 2. Increase in triglyceride content in rat liver was soon followed by the decrease of hepatic glycogen. 3. When rats were starved prior to introduction of autoxidized methyl linoleate, hepatic triglyceride accumulation did not occur. 4. The activities of α-glycerophosphate dehydrogenase and triglyceride synthetase in liver, and those of glutamic oxalacetic transaminase and leucine aminopeptidase in plasma were practically similar among the rats of test groups fed fresh or autoxidiz...

Inhibition of the peripheral activity of thyroid hormone by selected thio-compounds.

Approximately 40 thio-compounds of the 2-thiopyrimidine, 2-thioimidazole, 2-thiobarbituric acid and 2-thiohydantoin type were tested for their inhibitory effects on the induction of liver mitochondrial α-glycerophosphate dehydrogenase (GPD) activity by L-thyroxine (L-T4). Of the compounds tested, 5,5-diphenyl-2-thiohydantoin (DPTH) was found to be the most potent and blocked 80-90% of the GPD response to L-T4 doses as high as 40 μg injected sc per 100 g bw per day. Other compounds showing marked inhibitory activity were PTU (6-propyl- 2-thiouracil), DATB (5,5′-diallyl-2-thiobarbituric acid) and DTP (2,4-dithiopyrimidine). All of the above compounds produced elevated serum PBI concentrations when 15 jig of L-T4 was administered per 100 g bw per day. A number of other thyroxine analogs were also administered to rats receiving 0.06% PTU, DATB, DTP, 2-thiohydantoin (TH), 2-thiouracil (TU) and DPTH in the diet, but only DPTH inhibited the liver GPD response to the thyroxine analogs tested. The other thio-compo...

Biochemical maturation of flight muscle mitochondria in the colorado beetle, leptinotarsa decemlineata say

1. 1. The post-emergence maturation of Colorado beetle flight muscle mitochondria was studied under conditions leading to both diapause and non-diapause. 2. 2. The mitichondria showed an increase in respiratory activity with pyruvate/ malate and α-glycerophosphate as substrate during the first 6 days of flight muscle development. The respiration with succinate decreased during development. 3. 3. Both succinate and α-glycerophosphate dehydrogenase activities increased during the first 6 days. 4. 4. No significant changes in oxidative phosphorylation could be observed during development. 5. 5. Mitochondria from pre-diapause animals have the same characteristics as mitochondria from non-diapause animals. However, much less mitochondria could be isolated from pre-diapuase animals. 6. 6. The results suggest a long-term hormonal effect on mitochondriogenesis in the Colorado beetle.

Studies on the appearance of soluble α-glycerophosphate dehydrogenase activity during the development of the sheep blowfly Lucilia

1. 1.Early in the third instar, during larval development of Lucilia, α-glycerophosphate dehydrogenase activity per insect reached a peak corresponding to 12.5 per cent of the mature adult level. After puparium formation the activity per insect declined to about 2 per cent of the adult level. About 8 hours before adult emergence, the enzyme activity began to increase rapidly, rising tenfold in the next 2.3 days. Adult female flies were larger and contained more enzyme than males. Maximum enzyme activity was reached in the 4-day-old mature fly. In both 7-day-old male and female flies the enzyme activity began to decrease. 2. 2.The pattern of changes of the enzyme activity per mg. soluble protein (specific enzyme activity) over the life cycle was very similar to that of the enzyme activity per insect, except that the peak in mid-larval life was displaced forwards by 1 day and the magnitude of the increase over emergence was greater. This was a consequence of changes in soluble protein per insect, which increased fiftyfold in mid-larval life and declined by 42 per cent over the 8 hours spanning emergence. 3. 3.During the 4 days spanning adult emergence the specific enzyme activity increased eightfold in the head, two hundredfold in the thorax, and fourfold in in the abdomen. In newly emerged and 2-day-old flies 88 per cent and 95 per cent of the total enzyme activity was thoracic. 4. 4.Enzyme activity could not be elicited by mixing homogenates of insects of different ages. 5. 5.Cycloheximide at 1 μg. per insect inhibited by about 50 per cent the increase in specific enzyme activity of insects injected 3 hours before emergence and processed either at or a few hours after emergence. Cycloheximide injected into newly emerged flies produced inhibitions of 90 per cent over a 3-hour period. Inhibitions were always more pronounced for shorter periods of exposure to the inhibitor, regardless of when the insects were injected. 6. 6.Cycloheximide inhibited by about 30 per cent the decline in amount of soluble protein per insect over emergence; this inhibition persisted for longer periods than did that of enzyme formation.

Biochemical heterogeneity of rat liver mitochondria separated by rate zonal centrifugation.

1. Rat liver mitochondria were separated on the basis of their sedimentation coefficients in an iso-osmotic gradient of Ficoll-sucrose by rate zonal centrifugation. The fractions (33, each of 40ml) were collected in order of decreasing density. Fractions were analysed by spectral analysis to determine any differences in the concentrations of the cytochromes and by enzyme analyses to ascertain any differences in the activities of NADH dehydrogenase, succinate dehydrogenase and alpha-glycerophosphate dehydrogenase. 2. When plotted as% of the highest specific concentration, the contents of cytochrome a+a(3) and cytochrome c+c(1) were constant in all fractions but cytochrome b was only 65% of its maximal concentration in fraction 7 and increased with subsequent fractions. As a result, the cytochrome b/cytochrome a+a(3) ratio almost doubled between fractions 7 and 25 whereas the cytochrome c+c(1)/cytochrome a+a(3) ratio was unchanged. 3. Expression of the dehydrogenase activities as% of highest specific activity showed the following for fractions 6-26: NADH dehydrogenase activity remained fairly constant in all fractions; succinate dehydrogenase activity was 62% in fraction 6 and increased steadily to its maximum in fraction 18 and then decreased; the activity of alpha-glycerophosphate dehydrogenase was only 53% in fraction 6 and increased slowly to its peak in fractions 22 and 24. 4. These differences did not result from damaged or fragmented mitochondria or from microsomal contamination. 5. These results demonstrate that isolated liver mitochondria are biochemically heterogeneous. The importance of using a system for separating biochemically different mitochondria in studies of mitochondrial biogenesis is discussed.

Metabolic changes during spermatogenesis and thoracic tissue maturation in Drosophila hydei

In vitro enzyme studies indicate that gametes depend upon carbohydrate oxidation by way of the pentose shunt cycle, glycolysis, and the Krebs cycle for energy early in spermatogenesis in Drosophila hydei. Enzymes associated with amino acid metabolism and fatty acid synthesis are also high in activity at these developmental stages. In late spermiogenesis gametic glycolytic and Krebs cycle enzyme activities increase greatly. Both carbohydrates and amino acids are likely energy sources for mature spermatozoa. Low lactate dehydrogenase and β-hydroxyacyl dehydrogenase activities suggest that gametes at all developmental stages have low capacities for lactic acid formation and fatty acid oxidation. Thoracic tissue development differs fundamentally from testis development in that the α-glycerophosphate dehydrogenase-oxidase cycle becomes highly developed in thoracic tissue, whereas the low activity of α-glycerophosphate dehydrogenase indicates that it is a minor factor in gamete metabolism. Furthermore, NADP-isocitrate dehydrogenase and malic enzyme become increasingly less active as thoracic tissue matures, with malate dehydrogenase and NAD-isocitrate dehydrogenase becoming more active. The NADP-dependent enzymes are very active at all stages of spermatozoan development. Glycolytic and Krebs cycle enzyme activities are much higher in thoracic tissue at all maturation stages than in the mature testis.

Energy metabolism of the skeletal muscle of genetically dystrophic hamster.

The hind leg skeletal muscles of about 215-day-old genetically dystrophic hamsters (BIO strain 14.6) were found to contain subnormal concentrations of creatine phosphate, ATP, total adenine nucleotides, and NAD+ in comparison with those from the control animals. On the other hand, the levels of lactate, NADH, and NADPH were elevated without any significant changes in pyruvate, AMP, ADP, and NADP+ in the dystrophic muscle. The ratios of ATP/ADP and ATP/AMP were decreased and those of lactate/pyruvate, NADH/NAD+, and NADPH/NADP+ were increased in the dystrophic muscle. There are a number of similarities between the dystrophic and asphyxiated muscles with respect to energy metabolism; however, the possibility is not ruled out at present that the hypoxic-like changes in energy metabolism of the dystrophic muscle are due to mechanisms other than oxygen lack. The activity of glucose-6-phosphate dehydrogenase was increased whereas the activities of α-glycerophosphate dehydrogenase, glyceraldehyde phosphate dehydrogenase, lactate dehydrogenase, myokinase, and creatine phosphokinase were decreased in the dystrophic muscle. On the basis of our earlier and present results it is suggested that changes in the high energy phosphate stores in the genetically dystrophic hamster muscle are due to defects in both the processes of energy production and utilization.

Pathways of carbohydrate metabolism in Tetrahymena. Subcellular distribution and properties of hexokinase, aldolase and α-glycerophosphate dehydrogenase

In homogenates prepared at pH 6.8, most of the hexokinase activity of Tetrahymena was in soluble form, whereas in homogenates prepared at pH 7.9 most of the activity was localized on the mitochondria. The K m values for the hexokinase of Tetrahymena for glucose and for fructose are similar to the K m values for brain hexokinase and there was no appreciable difference in kinetic properties between enzyme bound to the mitochondria and enzyme released from the mitochondria. There was no indication of a specific fructokinase in Tetrahymena. Aldolase, fructose-1,6-diphosphatase, and α-glycerophosphate dehydrogenase activities were observed only in the cytosol. Some implications of these results with respect to glyconeogenic and glycolytic pathways in Tetrahymena are discussed.

Genetic Block of L-Glycerol-3-phosphate: NADP Oxidoreductase in the L-Glutamic Acid-producing Glycerol Auxotroph

Investigations were carried out to detect a blocked step in the glycerol biosynthesis of the glycerol auxotroph GL-21 derived from Corynebacterium alkanolyticum No. 314.The enzyme required for the conversion of dihydroxyacetone phosphate to α-glycerophosphate was assumed to be defective, because some of glycerol derivatives and glycerol analogues substituted for glycerol as a growth factor, in which glycerides, phospholipids, surfactants and intermediary metabolites in the glycolysis pathway were included.To confirm this assumption, the activities of α-glycerophosphate dehydrogenase of the mutant were compared to those of the parent. From these results, the auxotroph GL-21 was found to be deficient for a specific l-glycerol-3-phosphate: NADP oxidoreductase which is indispensable for the synthesis of glycerol.

On the Parafollicular Cells in the Thyroid Gland of the Bovine Foetus

The thyroids of 117 bovine foetuses were studied by some histochemical and selective staining methods with respect to the occurrence of parafollicular cells. Furthermore, 7 foetuses were studied by electron microscopy. The length of the foetuses varied from 6 to 72 cm corresponding to an estimated age of about 2 to 9 months. Parafollicular cells were observed in the thyroids of all foetuses examined. The ultrastructure of the parafollicular cells in the foetuses differed very little from that described in adult animals. Histochemically, Luxol fast blue positive phospholipids and α-glycerophosphate dehydrogenase activity could be observed in the cells. The Solcia-Sampietro method gave positive results in most of the foetuses examined. The reactions observed at light microscopic level were rather faint in the youngest foetuses. The functional aspects of the results are discussed.

Metabolic control mechanisms in mammalian systems. Involvement of adenosine 3':5'-cyclic monophosphate in androgen action.

1. The ability of exogenously administered cyclic AMP (adenosine 3':5'-monophosphate) to exert andromimetic action on certain carbohydrate-metabolizing enzymes was investigated in the rat prostate gland and seminal vesicles. 2. Cyclic AMP, when injected concurrently with theophylline, produced marked increases in hexokinase, phosphofructokinase, glyceraldehyde phosphate dehydrogenase, pyruvate kinase, and two hexose monophosphate-shunt enzymes, as well as alpha-glycerophosphate dehydrogenase activity in accessory sexual tissues of castrated rats. The 6-N,2'-O-dibutyryl analogue of cyclic AMP caused increases of enzyme activity that were greater than those induced by the parent compound. 3. Time-course studies demonstrated that, whereas significant increases in the activities of most enzymes occurred within 4h after the injection of cyclic AMP, maximal increases were attained at 16-24h. 4. Increase in the activity of the various prostatic and vesicular enzymes was dependent on the dose of cyclic AMP; in most instances, 2.5mg of the cyclic nucleotide/rat was sufficient to elicit a statistically significant response. 5. Administration of cyclic AMP and theophylline also produced stimulation of enzyme activities in secondary sexual tissues of immature rats. 6. Cyclic AMP and theophylline did not affect significantly any of the enzymes studied in hepatic tissue. 7. Stimulation of various carbohydrate-metabolizing enzymes in the prostate gland and seminal vesicles by cyclic AMP was independent of adrenal function. 8. Concurrent treatment with actinomycin or cycloheximide prevented the cyclic AMP- and theophylline-induced increases in enzyme activities in both castrated and adrenalectomized-castrated animals. 9. Administration of a single dose of testosterone propionate (5.0mg/100g) to castrated rats caused a significant increase in cyclic AMP concentration in both accessory sexual tissues. 10. In addition, treatment with theophylline potentiated the effects of a submaximal dose of testosterone (1.0mg/100g) on all those prostatic and seminal-vesicular enzymes that are increased by exogenous cyclic AMP. 11. The evidence indicates that cyclic AMP may be involved in triggering the known metabolic actions of androgens on secondary sexual tissues of the rat.

Biochemical alterations in the skeletal muscle of vitamin E deficient rats.

Rats were fed a vitamin E deficient diet for 5–10 weeks and the energy state of the hind leg muscle was examined. Both creatine phosphate and ATP were decreased by 64 and 22% of the control values, respectively, in the skeletal muscles of rats on the vitamin E deficient diet for 10 weeks, whereas ADP was increased by more than 100% without any significant changes in the level of AMP. The ratios ATP/ADP and ATP/AMP also declined markedly in the hind leg muscles of the rats on the vitamin E deficient diet for 10 weeks. The concentrations of NAD+ and NADPH decreased, whereas no significant changes in the levels of NADH and NADP+ were observed in the muscles of vitamin E deficient animals. Feeding a normal diet for 4 weeks to rats previously on the vitamin E deficient diet was found to restore the energy state of the muscle towards normal. Although no changes in the ultrastructure of the skeletal muscle were apparent, the levels of lactate and pyruvate as well as the lactate/pyruvate ratio were increased in vitamin E deficiency. The activities of lactate dehydrogenase and malate dehydrogenase were decreased whereas α-glycerophosphate dehydrogenase activity did not change significantly. These results indicate a dramatic alteration in skeletal muscle metabolism of vitamin E deficient rats. It is suggested that such a change may partly be due to a defect in the process of energy production.

Metabolic control mechanisms in mammalian systems. 8. Thyroid hormone control of alpha-glycerophosphate dehydrogenase activity in rat cerebral cortex and cerebellum.

The influence of thyroid hormone on soluble NAD-linked α-glycerophosphate dehydrogenase (α-GPDH) activity as well as the ontogeny and relative distribution of this enzyme were investigated in certain regions of the rat brain. In adult female rats, highest levels of enzyme activity were found in the brain stem and spinal cord; lowest activity was present in the cerebellum. Studies on the development of α-GPDH in the cerebral cortex and cerebellum revealed the presence of extremely low levels of enzyme activity at birth with rapid increases occurring within the first 30 days of life. These developmental increases in α-GPDH activity of the cerebral cortex and cerebellum were markedly impaired in rats made hypothyroid by treatment with 131I at 1 day of age. Whereas 50 μCi of 131I exerted no appreciable effect on the brain enzyme, 60% inhibition of α-GPDH was produced by 200 μCi of the radioisotope. Much less inhibition of enzyme activity in both cerebral cortex and cerebellum was observed when thyroidectomy was delayed for 20 days after birth. Treatment of young hypothyroid animals with L-triiodothyronine (T3) produced increases in cerebrocortical and cerebellar α-GPDH activity which were both time- and dose-dependent. However, when the initiation of T3 treatment was delayed until thyroidectomized animals reached adulthood, the hormone failed to produce any appreciable change in enzyme activity. Cycloheximide, an inhibitor of protein synthesis, prevented the T3-induced increases in brain α-GPDH in neonatally thyroidectomized animals, suggesting that the observed hormone-stimulated increases in enzyme activity may be the result of new enzyme synthesis. Evidence indicates that thyroid hormone plays an important role in the regulation of α-GPDH activity of the developing cerebral cortex and cerebellum.

Ethanol metabolism in rats treated with ethyl-α-p-chlorophenoxyiso-butyrate (Clofibrate)

Clofibrate treatment (60 mg/day/100 g body wt im. for nine days) increased the liver to body weight ratio of the rats by 71 %. The activity of mitochondrial α-glycerophosphate dehydrogenase in the liver of clofibrate-treated rats was five times greater than in normal rat liver. The amounts of cytochrome a and mitochondrial protein per gram of liver wet weight were not changed. Clofibrate treatment increased the oxygen consumption of liver slices by 16 %. Ethanol increased the lactate/pyruvate ratio (an index of the redox state in the cytosolic compartment of the liver cell) in perfused normal livers and only slightly in the livers from clofibrate-treated rats. This effect of clofibrate is similar to that of thyroxine and seems to be due to enzyme induction, as diethylaminoclofibrate hydrochloride added in vitro did not prevent ethanol-induced increase in hepatic lactate/pyruvate ratio. Clofibrate treatment in rats significantly increased the disappearance rate of ethanol. The activity of hepatic alcohol dehydrogenase per gram of liver wet weight of per milligram of soluble protein was not changed by clofibrate treatment.

Cytochemical observations on glucose-6-phosphatase, glucosan phosphorylase, glucose-6-phosphate dehydrogenase, and α-glycerophosphate dehydrogenase in chick liver cell cultures infected with Trichomonas vaginalis

Cytochemical reactions specific for glucose-6-phosphatase, glucosan phosphorylase, glucose-6-phosphate dehydrogenase, and α-glycero-phosphate dehydrogenase were observed in the epithelial cells and macrophages of chick liver cell cultures; α-glycerophosphate dehydrogenase activity was observed also in the fibroblasts. Distribution of three of the enzymes was limited to the cytoplasm, their activity being localized primarily in cytoplasmic inclusions. Weak staining of the nuclei and strong staining of the nucleoli occurred in addition to the cytoplasmic reaction in cells treated for glucose-6-phosphatase. In cell cultures inoculated with Trichomonas vaginalis, the activity of three of the enzymes decreased progressively in the course of infection, but that of α-glycerophosphate dehydrogenase increased.

Effect of ethanol on glycerol metabolism in rat liver during different hormonal conditions

The effect of ethanol on the metabolism of glycerol and its regulation was studied in rat liver in vitro, under different hormonal conditions. Glycerol utilization by normal rat liver slices is inhibited to about 50 per cent upon addition of ethanol. Ethanol addition to normal animals increases hepatic concentrations of α-glycerophosphate and 5'AMP, which have been observed to inhibit hepatic glycerokinase. Glucagon administration to normal animals also causes an increase in hepatic α-glycerophosphate and 5'AMP content and consequently lowers glycerol utilization. Insulin administration neither effects α-glycerophosphate, AMP content, nor the rate of glycerol utilization. In alloxan diabetes, although α-glycerophosphate concentration is lowered, glycerol utilization is not different from normals as hepatic AMP concentrations are doubled. Blocking ofglycolysis by 2-deoxyglucose-6-phosphate lowers ethanol mediated accumulation of α-glycerophosphate in insulin and glucagon treated groups. Ethanol addition causes an increase in glycerol release from all groups, except that treated with insulin. The activities of hepatic glycerokinase and α-glycerophosphate dehydrogenase in the insulin treated or diabetic groups are not different from the control group. This investigation shows that an increase in either of the two inhibitors of glycerokinase, namely aglycerophosphate, or 5'AMP can result in an inhibition of hepatic glycerol utilization.