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PubMed1985

Purification and properties of myo-inositol-1-phosphatase from rat brain.

myo-Inositol-1-phosphatase [EC 3.1.3.25] was purified from a cytosolic fraction of rat brain. The purified enzyme appeared homogeneous on SDS-polyacrylamide gel electrophoresis and its molecular weight was estimated to be 29,000. The molecular weight of the native enzyme was 55,000 as determined by molecular sieve chromatography. These values indicated that the native enzyme was composed of two identical subunits. The isoelectric point of the enzyme was 4.6. The enzyme hydrolyzed inositol-1-phosphate, 2'-AMP, 2'-GMP, beta-glycerophosphate, and alpha-glycerophosphate; the ratio of the reaction rates was 100 : 84 : 73 : 64 : 32. The Km values for inositol-1-phosphate, 2'-AMP, and beta-glycerophosphate were 1.2 X 10(-4) M, 1.9 X 10(-4) M, and 7.7 X 10(-4) M, respectively. Mn2+ and Ca2+ were strong competitive inhibitors against Mg2+, with Ki values of 3 microM and 20 microM, respectively. This result suggests that myo-inositol-1-phosphatase might be regulated by intracellular Ca2+ and/or Mn2+. Li+, which is known to show a therapeutic effect on manic-depressive disease and also to prolong the intrinsic periods of circadian rhythms in various organisms, was a potent uncompetitive inhibitor and inhibited 50% of the activity at 1 mM. The possibility that myo-inositol-1-phosphatase and inositol phospholipid metabolism are involved in circadian rhythm oscillation is discussed in terms of Li actions.

Animals↗

PubMed1982

myo-Inositol-1-Phosphatase from the Pollen of Lilium longiflorum Thunb.

A Mg(2+)-dependent, alkaline phosphatase has been isolated from mature pollen of Lilium longiflorum Thunb., cv. Ace and partially purified. It hydrolyzes 1l- and 1d-myo-inositol 1-phosphate, myo-inositol 2-phosphate, and beta-glycerophosphate at rates decreasing in the order named. The affinity of the enzyme for 1l- and 1d-myo-inositol 1-phosphate is approximately 10-fold greater than its affinity for myo-inositol 2-phosphate. Little or no activity is found with phytate, d-glucose 6-phosphate, d-glucose 1-phosphate, d-fructose 1-phosphate, d-fructose 6-phosphate, d-mannose 6-phosphate, or p-nitrophenyl phosphate. 3-Phosphosphoglycerate is a weak competitive inhibitor. myo-Inositol does not inhibit the reaction. Optimal activity is obtained at pH 8.5 and requires the presence of Mg(2+). At 4 millimolar, Co(2+), Fe(2+) or Mn(2+) are less effective. Substantial inhibition is obtained with 0.25 molar Li(+). With beta-glycerophosphate as substrate the K(m) is 0.06 millimolar and the reaction remains linear at least 2 hours. In 0.1 molar Tris, beta-glycerophosphate yields equivalent amounts of glycerol and inorganic phosphate, evidence that transphosphorylation does not occur.In higher plants this myo-inositol-1-phosphatase links myo-inositol biosynthesis to the myo-inositol oxidation pathway to produce an alternative path from d-glucose 6-phosphate to UDP-d-glucuronate that bypasses UDP-d-glucose dehydrogenase. myo-Inositol-1-phosphatase also furnishes free myo-inositol for reactions that lead to other cyclitols and cyclitol-containing compounds of biosynthetic and/or regulatory significance in plant growth and development.

Journal Article↗

PubMed1987

Enzyme levels of the NADH shuttle systems: measurements in isolated muscle fibres from humans of differing physical activity.

The aim of the present study was to investigate enzyme levels of the malate-aspartate and alpha-glycerophosphate shuttles in type I (slow-twitch) and type II (fast-twitch) fibres of human skeletal muscle. The influence of endurance training on these levels was also elucidated. Biopsy specimens were obtained from the lateral part of the quadriceps femoris muscle of six untrained and six endurance-trained subjects. Type I vs. type II. In both groups the type I fibres exhibited higher levels of the TCA cycle marker enzyme citrate synthase (CS), as well as of the malate-aspartate shuttle enzymes (cytoplasmic and mitochondrial malate dehydrogenase (cMDH, mMDH), and aspartate aminotransferase (cASAT, mASAT]. A more pronounced difference between type I and type II fibres was noted for cMDH (58%) than for mMDH (16%), cASAT (20%), mASAT (18%) and CS (25%). In contrast to these enzymes, the levels of cytoplasmic glycerol-3-phosphate dehydrogenase (cGPDH), the enzyme representative of the alpha-glycerophosphate shuttle, were higher (25%) in the type II fibres. Endurance-trained vs. untrained. In the endurance-trained group, both fibre types were characterized by higher levels of CS (mean for both fibre types: 48%) as well as of mitochondrial malate-aspartate shuttle enzymes (mMDH: 47%, mASAT: 48%) than in the corresponding fibre types in the untrained group, while the differences in the levels of cytoplasmic malate-aspartate shuttle enzymes (cMDH: 13%, cASAT: 16%) were not statistically significant. Nor were the differences in cGPDH levels (8%) between the untrained and endurance-trained groups statistically significant. It is concluded that in human skeletal muscle, malate-aspartate shuttle enzymes are expressed to a higher degree in type I (slow) fibres than in type II (fast) fibres, with cMDH exhibiting the most marked difference. The single fibre analysis indicated that the muscle's activity level might exert a greater influence on the mitochondrial isoenzymes than on the cytoplasmic ones. In contrast to the malate-aspartate shuttle enzymes, the alpha-glycerophosphate shuttle is expressed to a higher degree in type II fibres and its capacity appears to not be influenced by endurance training. The present studies demanded considerable methodological investigations which also are presented in this paper.

Adult↗

PubMed1985

Biosynthesis of D-alanyl-lipoteichoic acid by Lactobacillus casei: interchain transacylation of D-alanyl ester residues.

Lipoteichoic acid (LTA) from Lactobacillus casei contains poly(glycerophosphate) substituted with D-alanyl ester residues. The distribution of these residues in the in vitro-synthesized polymer is uniform. Esterification of LTA with D-alanine may occur in one of two modes: (i) addition at random or (ii) addition at a defined locus in the poly(glycerophosphate) chain followed by redistribution of the ester residues. A time-dependent transacylation of these residues from D-[14C]alanyl-lipophilic LTA to hydrophilic acceptor was observed. The hydrophilic acceptor was characterized as D-alanyl-hydrophilic LTA. This transacylation requires neither ATP nor the D-alanine incorporation system, i.e., the D-alanine activating enzyme and D-alanine:membrane acceptor ligase. No evidence for an enzyme-catalyzed transacylation reaction was observed. We propose that this process of transacylation may be responsible for the redistribution of D-alanyl residues after esterification to the poly(glycerophosphate). As a result, it is difficult to distinguish between these proposed modes of addition.

Acylation↗

PubMed1983

Effects of hormones on the maintenance and mitochondrial functions of rat hepatocytes cultured in serum-free medium.

The survival and morphology of rat hepatocytes were examined in primary cell cultures that were maintained in serum-free medium supplemented with different hormones. Insulin and dexamethasone improved survival and maintenance of normal epithelial-shaped cells, although triiodothyronine did not alter cell survival or morphology when added to the medium alone or with other hormones. The level of mitochondrial alpha-glycerophosphate dehydrogenase and cytochromes a(+a3), b and c, but not c1, were increased in cultured hepatocytes by triiodothyronine. Although induction of alpha-glycerophosphate dehydrogenase did not require serum or growth hormone, the triiodothyronine effect was potentiated by insulin plus dexamethasone. This permissive effect of dexamethasone parallels its known glucocorticoid action of increasing the activity of the gluconeogenic enzyme tyrosine aminotransferase in the cultured hepatocytes. Glucagon, which also elevated tyrosine aminotransferase activity, had no effect upon the induction of alpha-glycerophosphate dehydrogenase by triiodothyronine. Since the culture medium was completely defined and triiodothyronine did not alter survival or morphology of the hepatocytes, the effects upon mitochondrial functions are direct cellular actions of the thyroid hormone.

Animals↗

PubMed1981

The influence of thyroidal status on rat hepatic mitochondrial NADH duroquinone reductase.

Hepatic mitochondrial NADH duroquinone reductase and alpha-glycerophosphate dehydrogenase activities were measured in rats with altered thyroidal status. Whereas alpha-glycerophosphate dehydrogenase activity was decreased in hypothyroid rats, NADH duroquinone reductase was increased approximately 3-fold in both thiouracil-fed and thyroidectomized rats. In hyperthyroid animals, NADH duroquinone reductase activity was decreased, whereas there was the expected elevation in mitochondrial alpha-glycerophosphate dehydrogenase. Maximum velocity measurements of NADH duroquinone reductase demonstrated that the increase in enzyme activity associated with hypothyroidism occurred without an alteration in Michaelis constants for the reaction. Rats bearing mammary carcinomas induced by N-nitrosomethylurea also showed an increase in hepatic NADH duroquinone reductase when rendered hypothyroid, but the enzyme was unaffected by thyroxine administration.

Animals↗

PubMed1983

Development of brown adipose tissue thermogenesis in the ovine fetus and newborn.

Despite the importance of brown adipose tissue (BAT) in the regulation of thermogenesis and energy expenditure in both newborn and adult mammals, the functional ontogenesis of this tissue is largely unknown. In the present study, we describe the maturation of several aspects of BAT thermogenesis in fetal and newborn sheep. Cell respiration of brown adipocytes isolated from perirenal BAT was measured using a Gilson differential respirometer. Cells were isolated from four fetal animals at 121-124 days gestation (group 1), five fetal animals at 137-140 days gestation (group 2), and five newborns between birth and 4 days of age (group 3). In addition to basal oxygen consumption, in vitro cell respiration also was measured after the addition of norepinephrine (NE), (Bu)2cAMP, alpha-glycerophosphate (alpha GP), and butyric acid. Mean (+/- SEM) basal respiration (in microliters of O2 per 10(6) cells/h) increased from 11 +/- 1 in group 1 to 31 +/- 2 in group 2 and 45 +/- 7 in group 3. Cell volume increased from 9 +/- 1 pl in group 1 to 13 +/- 2 pl in group 2 and 18 +/- 2 pl in group 3. After adjustment for variations in basal respiration due to differences in cell volume, basal respiration in group 2 was greater than that in group 1 and equal to that in group 3. Maximal NE (10(-6) M)-stimulated respiration increased from 74 +/- 16 in group 1 to 294 +/- 47 in group 2. Maximal NE-stimulated respiration in group 3 (133 +/- 30) was less than that in group 2, but equal to that in group 1. (Bu)2cAMP-stimulated respiration increased from 51 +/- 12 in group 1 to 175 +/- 22 in group II, with no further increase in group III. Neither NE- nor (Bu)2cAMP-stimulated respiration varied significantly with cell volume. alpha GP substrate respiration demonstrated significant increases from group 1 to group 2, with another significant increase in Group 3. Butyric acid substrate respiration in group 1 was less than those measured in groups 2 and 3, while respiration values in groups 2 and 3 were equal. After adjustments for variations due to differences in cell volume, the patterns of development of both alpha GP and butyric acid substrate respiration were unaltered. The following conclusions were reached 1) Full maturation of BAT catecholamine-stimulated cellular respiration occurs before delivery near term in the ovine fetus. 2) In the neonatal lamb, a decrease in catecholamine-stimulated respiration occurs without a decrease in (Bu)2cAMP-stimulated respiration. This suggests that a decrease in BAT sensitivity to NE occurs after delivery at the receptor adenyl cyclase level. 3) The perinatal increase in alpha GP substrate respiration without an increase in butyric acid substrate respiration suggests that mitochondrial alpha-glycerophosphate dehydrogenase activity is increased. This was confirmed by measuring increased alpha-glycerophosphate dehydrogenase activity in crude BAT mitochondrial fractions in group 3 animals.

Adipose Tissue, Brown↗

PubMed1992

Long term in vitro effects of streptozotocin, interleukin-1, and high glucose concentration on the activity of mitochondrial dehydrogenases and the secretion of insulin in pancreatic islets.

When cultured mouse pancreatic islets were exposed for 30 min to streptozotocin (STZ; 1.8 mM) and then maintained for 7 days in tissue culture, they displayed a decreased secretory response to D-glucose and an impairment of both FAD-linked glycerophosphate dehydrogenase and NAD-dependent 2-ketoglutarate dehydrogenase specific activities, with little change in either NAD-linked glycerophosphate dehydrogenase or glutamate dehydrogenase activity. The enzymatic defect was not reproduced by prolonged exposure of either rat islets to interleukin-1 (10 U/ml) or mouse islets to a high concentration of D-glucose (28 mM). In the former, but not latter, situation, the secretory response to D-glucose was again impaired. These findings reveal that STZ, but not all beta-cytotoxic agents, lowers the activity of selected islet mitochondrial dehydrogenases. Such enzymatic defects, especially the suppression of FAD-linked glycerophosphate dehydrogenase, may explain the preferential alteration of the B-cell metabolic and secretory responses to D-glucose, as previously observed in islets of adult rats injected with STZ during the neonatal period.

Animals↗

PubMed1999

1,25-(OH)2D3 down-regulates expression of Phex, a marker of the mature osteoblast.

Mutations in the PHEX/Phex gene, which encodes for a protein with homology to neutral endopeptidases, are responsible for human and murine X-linked hypophosphatemia. The present study examined Phex messenger RNA (mRNA) and protein expression in cultured osteoblasts and its regulation by 1,25-(OH)2D3. Phex mRNA levels were quantitated on Northern blots by densitometric analysis relatively to GAPDH mRNA levels. Immunoreactive Phex protein levels were evaluated by immunoprecipitation using a polyclonal rabbit antiserum raised against a mouse Phex carboxy-terminal peptide. Beta-glycerophosphate-induced matrix mineralization in primary osteoblast cultures was associated with significant increases in Phex mRNA and protein. Phex mRNA and protein levels were low or undetectable in proliferating preosteoblastic MC3T3-E1 cells and dramatically increased concomitantly with initiation of matrix mineralization. The pattern of Phex expression, however, was similar in nonmineralizing cultures grown in the absence of beta-glycerophosphate, indicating that the induction of Phex expression in MC3T3-E1 cells was related to cell differentiation rather than matrix mineralization. 1,25-(OH)2D3 inhibited mineral deposition and down-regulated Phex mRNA and protein expression in a time- and dose-dependent manner. These results indicate that Phex is a marker of the fully differentiated osteoblast and that its expression is stimulated during beta-glycerophosphate-induced mineralization in primary osteoblast cultures and down-regulated by 1,25-(OH)2D3, an inhibitor of matrix mineralization. These findings add support for Phex having an important role in bone mineralization.

Animals↗

PubMed1989

Oxidative properties of carp red and white muscle.

Substrate preferences of isolated mitochondria and maximal enzyme activities were used to assess the oxidative capacities of red muscle (RM) and white muscle (WM) of carp (Cyprinus carpio). A 14-fold higher activity of citrate synthase (CS) in RM reflects the higher mitochondrial density in this tissue. RM mitochondria oxidize pyruvate and fatty acyl carnitines (8:O, 12:O, 16:O) at similarly high rates. WM mitochondria oxidize these fatty acyl carnitines at 35-70% the rate of pyruvate, depending on chain length. WM has only half the carnitine palmitoyl transferase/CS ratio of RM, but similar ratios of beta-hydroxyacyl CoA dehydrogenase/CS. Ketone bodies are poor substrates for mitochondria from both tissues. In both tissues mitochondrial alpha-glycerophosphate oxidation was minimal, and alpha-glycerophosphate dehydrogenase was present at low activities, suggesting the alpha-glycerophosphate shuttle is of minor significance in maintaining cytosolic redox balance in either tissue. The mitochondrial oxidation rates of other substrates relative to pyruvate are as follows: alpha-ketoglutarate 90% (RM and WM); glutamate 45% (WM) and 70% (RM); proline 20% (WM) and 45% (RM). Oxidation of neutral amino acids (serine, glycine, alanine, beta-alanine) was not consistently detectable. These data suggest that RM and WM differ in mitochondrial properties as well as mitochondrial abundance. Whereas RM mitochondria appear to be able to utilize a wide range of metabolic fuels (fatty acids, pyruvate, amino acids but not ketone bodies), WM mitochondria appear to be specialized to use pyruvate.

Animals↗

PubMed1995

The Effect of Basic Fibroblast Growth Factor on the Reversion of Omental Adipocytes from Lean and Obese Patients.

BACKGROUND: this study was designed to characterize some of the biochemical and molecular genetic changes during reversion of human fat cells. METHODS: mature adipocytes were isolated from greater omental fat tissue of eight lean and 14 massively obese persons by established methodology. RESULTS: at day 7 of adherence to Leighton tubes, there was appreciable depletion of triacylglycerol, as well as assumption of an elongated contour. Relatedly, there was an increase in the expression of Beta-actin mRNA and a significant decrease in the specific activity of cytosolic glycerophosphate dehydrogenase. The decrement in the specific activity of glycerophosphate dehydrogenase, after 7 days in culture, was significant at p < 0.001. Basic fibroblast growth factor at 10 ngml(1) accelerated significantly (p < 0.03) the decrease in the specific activity of glycerophosphate dehydrogenase in adipose cells from lean subjects. In contrast, basic fibroblast growth factor had no significant influence on cells from massively obese persons. CONCLUSION: such resistance may contribute to the intractability of massive obesity.

Journal Article↗

PubMed1979

Shuttles for translocation of NADH in isolated liver cells from fed rats during oxidation of xylitol.

Translocation of xylitol-derived NADH via malate-aspartate and alpha-glycerophosphate shuttles was studied in liver cells isolated from fed rats. In bicarbonate medium amino-oxyacetate, rotenone and antimycin A, were equally efficient in depressing the xylitol removal. Incubation of cells in nonbicarbonate medium did not affect the rate of xylitol removal. In this medium amino-oxyacetate and antimycin A, but not rotenone, inhibited xylitol removal. Xylitol inhibited the lactate accumulation found when the cells were incubated without any exogenous substrates. Glucose was the main end product of xylitol oxidation. In nonbicarbonate medium ketogenesis was high, whereas in bicarbonate medium a low rate of ketone body formation was found. Xylitol had no effect on the rate of ketone body formation in either medium tested. Xylitol markedly decreased the ATP and Pi contents of the cells, but no change in the ATP/ADP x Pi ratio or the rate of oxygen consumption was found. The results suggest that NADH formed during xylitol oxidation is translocated to the mitochondria mainly through the malate-aspartate shuttle and only when this shuttle is inhibited does the alpha-glycerophosphate shuttle transfer NADH. Intramitochondrial reactions which form NADH and FADH2 are also suggested to be important regulators of the activity of the alpha-glycerophosphate shuttle.

Animals↗

PubMed1976

[Shifts in several aspects of phospholipid metabolism in the brains of white rats with radiation sickness].

Sublethal (400) and lethal (1600) doses of roentgen decrease the level of neutral phospholipids of rat brain and increase that of acid phospholipids. With the development of radiation disease the content of free glycerine and glycerophosphate increases and the glycerokinase and glycolytic pathways of glycerophosphate biosynthesis are activated together with the intensification of the direct and reverse reactions catalyzed by glycerophosphate dehydrogenase. The permeability of the artificial bimolecular phospholipid membranes prepared from rat brain phospholipid extracts is significantly increased at the end of the radiation.

Animals↗

PubMed1992

The early triiodothyronine-induced changes in state IV respiration is not regulated by the proton permeability of the mitochondrial inner membrane.

The time course of changes in mitochondrial respiration, alpha-glycerophosphate dehydrogenase activity, and inner membrane proton permeability and the effects of protein synthesis inhibition was determined in hypothyroid rats treated with triiodothyronine. Respiratory rates, alpha-glycerophosphate dehydrogenase activity and proton permeability were decreased in hypothyroid rats and rose to euthyroid levels 9-12 hours after triiodothyronine treatment. Some rats received actinomycin D with the hormone to inhibit protein synthesis. Sixteen hours after actinomycin D and hormone treatment, the increases in respiratory rates and in alpha-glycerophosphate dehydrogenase activity, were completely inhibited. However, actinomycin D did not inhibit the increase in the membrane's permeability.

Animals↗

PubMed1976

Hypophosphatasia: a cytochemical study of phosphatase activities.

Skeletal abnormalities with defective formation of mature calcified bone are the most prominent clinical features of hypophosphatasia. Low concentrations of serum and tissue alkaline phosphatase and elevated plasma and urinary levels of phosphorylethanolamine (PEA) are also present. Although PEA is hydrolyzed by serum alkaline phosphatase, the relationship between PEA and the deficiency is unclear. PEA has not previously been tested as a cytochemical substrate for the in situ demonstration of human alkaline phosphatase activity. We have studied alkaline phosphatase activity in hypophosphatasia in tissue sections, utilizing PEA and adenosinetriphosphate (ATP) as well as the usual beta-glycerophosphate and naphthol phosphate substrates. Neutral and acid phosphatase activities were also examined. Our results demonstrate that PEA is a substrate for the localization of alkaline phosphatase in normal human tissue, but is not hydrolyzed in hypophosphatasia in the liver, brain or costochondral junction under alkaline conditions. In the kidney in hypophosphatasia only the straight segments of proximal tubules that rim the medullary rays are reactive with PEA. Similar results in hypophosphatasia were obtained at an alkaline pH with ATP, beta-glycerophosphate, and naphthol phosphate. However, the defect in hypophosphatasia is not a generalized deficiency of membrane-associated phosphatases because membranes that were deficient in alkaline phosphatase activity demonstrated normal reactivity with ATP at neutral pH. In addition, thiamine pyrophosphate was also split by Golgi membranes within the cytoplasm. Acid hydrolysis of beta-glycerophosphate by lysosomes was normal.

Alkaline Phosphatase↗

PubMed1979

Ontogeny of glycerolipid biosynthetic enzymes in swine liver and adipose tissue.

Enzymes associated with glycerolipid biosynthesis were examined in microsomal fractions of liver and adipose tissue obtained from swine of various ages. Generally, liver glycerophosphate acyltransferase, phosphatidate phosphohydrolase, diglyceride acyltransferase, and choline phosphotransferase activities were substantial at birth but increased 2- to 3-fold by day 14 postpartum, decreased at day 25, then increased at the oldest ages studied (up to 155 days postpartum). In adipose tissue, enzyme activities were low at birth and developed through day 25 in a pattern generally similar to that observed in liver. In contrast to liver, the adipose enzymes were depressed immediately postweaning (day 32) with subsequent recovery. The observed decline in adipose tissue enzyme activities expressed on a tissue basis at older ages was primarily the result of increased adipocyte size, since the activities expressed on a cell basis did not decline as rapidly. In both liver and adipose tissue, phosphatidate was the major glycerolipid synthesized by the microsomal glycerophosphate acyltransferase enzymes at all ages (generally greater than 75%). The ratio of neutral lipids to phospholipids produced by acylation of glycerophosphate was increased when a microsomal--cytosolic preparation was used as a source of enzyme in contrast to a microsomal preparation.

Acyltransferases↗

PubMed1990

[A chronobiological analysis of the lymphocyte dehydrogenase activity in the peripheral blood of rats with Walker 256 carcinosarcoma].

In a series of experiments the alpha-glycerophosphate dehydrogenase and succinate dehydrogenase (SDH) activities were daily determined simultaneously by the cytochemical method in peripheral blood lymphocytes of normal rats and those with the Walker carcinosarcoma. Using an original algorithm a hierarchy of biorhythms was singled out by a computer according to individual changes in the dehydrogenase activity for each rat. The mean level of succinate dehydrogenase activity was higher than that of alpha-glycerophosphate dehydrogenase. A set of discovered biorhythms and their representation were identical in the both enzymes. The tumor transplantation caused changes in the phase coordination of investigated dehydrogenases in all rhythms and promoted an increase of the succinate dehydrogenase amplitude as compared with the alpha-glycerophosphate dehydrogenase amplitude in certain rhythms. It is concluded that biorhythmological parameters of these enzymes may be used for characterization of the tumor-bearing host.

Animals↗

PubMed1975

Enzyme histochemical observations on the segmentation of the proximal tubules in the kidney of the female rat.

The segmentation of the proximal tubules in the kidney of the female rat was studied by means of enzyme histochemical reactions and the results compared with those observed in male and recently described by Jacobsen and J0rgensen (1973 a). Reactions were performed for the following soluble, coezyme-dependent oxido-reductases: glucose 6-phosphate dehydrogenase, alpha-glycerophosphate dehydrogenase, 3 alpha-hydroxysteroid dehydrogenase, NAD-as well as NADP-dependent isocitrate dehydrogenases, NAD-dependent malate dehydrogenase, NADP-dependent, decarboxylating malate dehydrogenase, uridine diphosphate glucose dehydrogenase. Measures were taken to reduce enzyme diffusion and eliminate interference from tissue tetrazolium reductases. Furthermore, reactions were performed for a number of less soluble or insoluble enzymes: glucose 6-phosphatase, mitochondrial alpha-glycerophosphate dehydrogenase, beta-hydroxybutyrate dehydrogenase, succinate dehydrogenase and tetrazolium reductases. In the proximal tubules of the female rat all enzymes studied--except beta-hydroxybutyrate dehydrogenase--showed segmental differences, most of them clearly revealing three segments. Sex differences were found concerning all enzymes except uridine diphosphate glucose dehydrogenase and NADP-dependent isocitrate dehydrogenase. The most pronounced sex-related differences were seen in the third segment in which part the male rat showed highest activity in respect to tetrazolium reductases, NAD-dependent isocitrate dehydrogenase, succinate dehydrogenase, beta-hydroxybutyrate dehydrogenase, 3 alpha-hydroxysteroid dehydrogenase and glucose 6-phosphate dehydrogenase and the female in respect to glucose 6-phosphatase, alpha-glycerophosphate dehydrogenases, and NADP-dependent, decarboxylating malate dehydrogenase. A few of the enzymes exhibited minor sex differences in the first two segments.

Animals↗