Long-term adaptive response to dietary protein of hexose monophosphate shunt dehydrogenases in rat kidney tubules

We have studied the effects of several different macronutrients on the kinetic behaviour of rat renal glucose 6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH). Rats were meal-fed with high-carbohydrate/low-protein, high-protein/low-carbohydrate and high-fat diets. High-protein increased renal G6PDH and 6PDGH activities by 66 per cent and 70 per cent respectively, without significantly changing the Km values of either and each Hexose monophosphate dehydrogenase activity increased steadily, reaching a significant difference on day 4. A rise in carbohydrate or fat in the diets, produced no significant change in either the activity or the kinetic parameters, Vmax and Km of the two dehydrogenases. In addition, the administration of a high-protein diet for 8 days significantly increased both the pentose phosphate pathway flux (92.6 per cent) and the kidney weigth (35 per cent), whereas no significant changes in these parameters were found when the animals were treated with the other diets. Our results suggest that an increase in the levels of dietary protein induces a rise in the intracellular levels of these enzymes. The possible role of this metabolic pathway in the kidneys under these nutritional conditions is also discussed.     

Influence of experimental diabetes on the kinetic behaviour of renal cortex hexose monophosphate dehydrogenases

1. Short term (1-2 hr) and long-term (2 days) effects of experimental alloxan induced diabetes on the kinetics of the renal hexose monophosphate shunt dehydrogenases are reported. 2. Alloxan diabetes for 2 days significantly increased kidney weight (16%) adding about 80 mg/day per g of kidney. No significant changes were found in renal growth 1-2 hr after alloxan injection. 3. Under these experimental conditions, the activities of glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase significantly increased (103 and 33% respectively) at all substrate concentrations, without affecting the KmS of either enzyme. 4. There was no effect of alloxan on the activity of these enzymes at 1-2 hr. Saturation curves show that all enzymes exhibited a M-M kinetic without evidence of sigmoidicity. 5. The results suggest that increased renal hexose monophosphate dehydrogenases activities are due to increased concentrations of the rate limiting proteins. 6. The relationship between these changes and renal hypertrophy is also discussed.     

The stereospecificity of sequential nicotinamide-adenine dinucleotide-dependent oxidoreductases in relation to the evolution of metabolic sequences.

The generalization that 'when a metabolic sequence involves consecutive nicotinamide-adenine dinucleotide-dependent reactions, the dehydrogenases have the same stereospecificity' was tested and confirmed for three metabolic sequences. (1) NAD+-xylitol (D-xylulose) dehydrogenase and NADP+-xylitol (L-xylulose) dehydrogenase are both B-specific. (2) D-Mannitol 1-phosphate dehydrogenase and D-sorbitol 6-phosphate dehydrogenase are both B-specific. (3) meso Tartrate dehydrogenase and oxaloglycollate reductive decarboxylase are both A-specific. Other dehydrogenases associated with the metabolism of meso-tartrate in Pseudomonas putida, such as hydroxypyruvate reductase and tartronate semialdehyde reductase, were also shown to be A-specific. Malate dehydrogenase from Pseudomonas putida was A-specific, and the proposition is discussed that the common A-stereospecificity among the dehydrogenases involved in meso-tartrate metabolism reflects their origin from malate dehydrogenase.     

Isoenzyme Patterns of Root and Shoot in the Early Growth of Wheat

Isoenzyme patterns of peroxidase, catalase, glucose-6-phosephate, glutamate and isocitrate dehydrogenases, esterase, amylase and IAA oxidase in the embryos, endosperms, roots and shoots of wheat seedlings (Triticum aestivum L. var. Nung-da 139) were determined by horizontal starch gel electrophoresis and polyacrylamide gel disc electrophoresis respectively. The number of isoenzymes of peroxidasc and amylase was increased with the concomitant increase of days during germination. The isoenzyme bands of esterase, glutamate, glucose-6-phosphate and isocitrate dehydrogenases in the embryos were more in the begining of germination. The activities of pero- xidase, IAA oxidase and glutamate dehydrogenase in roots were higher than those in shoots. On the contrary, the activities of catalase and glucose-6-phosphate dehydrogenase in shoots were higher than those in roots. However the activity of esterasc was slight higher in shoots. There was no difference in the activity of isocitrate dehydrogenase between roots and shoots. The morphological difference of shoot and root is evidently related to isoenzyme patterns. This investigation indicates that different metabolic characters are existed in shoot and root during differentiation.     

Renal enzymes during experimental diabetes mellitus in the rat. Role of insulin, carbohydrate metabolism, and ketoacidosis

The activities of various ammoniagenic, gluconeogenic, and glycolytic enzymes were measured in the renal cortex and also in the liver of rats made diabetic with streptozotocin. Five groups of animals were studied: normal, normoglycemic diabetic (insulin therapy), hyperglycemic, ketoacidotic, and ammonium chloride treated rats. Glutaminase I, glutamate dehydrogenase, glutamine synthetase, phosphoenolpyruvate carboxykinase (PEPCK), hexokinase, phosphofructokinase, fructose-1,6-diphosphatase, malate dehydrogenase, malic enzyme, and lactate dehydrogenase were measured. Renal glutaminase I activity rose during ketoacidosis and ammonium chloride acidosis. Glutamate dehydrogenase in the kidney rose only in ammonium chloride treated animals. Glutamine synthetase showed no particular variation. PEPCK rose in diabetic hyperglycemic animals and more so during ketoacidosis and ammonium chloride acidosis. It also rose in the liver of the diabetic animals. Hexokinase activity in the kidney rose in diabetic insulin-treated normoglycemic rats and also during ketoacidosis. The same pattern was observed in the liver of these diabetic rats. Renal and hepatic phosphofructokinase activities were elevated in all groups of experimental animals. Fructose-1,6-diphosphatase and malate dehydrogenase did not vary significantly in the kidney and the liver. Malic enzyme was lower in the kidney and liver of the hyperglycemic diabetic animals and also in the liver of the ketoacidotic rats. Lactate dehydrogenase fell slightly in the liver of diabetic hyperglycemic and NH4Cl acidotic animals. The present study indicates that glutaminase I is associated with the first step of increased renal ammoniagenesis during ketoacidosis. PEPCK activity is influenced both by hyperglycemia and ketoacidosis, acidosis playing an additional role. Insulin appears to prevent renal gluconeogenesis and to favour glycolysis. The latter would seem to remain operative in hyperglycemic and ketoacidotic diabetic animals.     

Decrease of Glucose 6-Phosphate and 6-Phosphogluconate Dehydrogenase Activities in the Xylem of Populus gelrica on Budding

The activities of glucose 6-phosphate and 6-phosphogluconate dehydrogenases, transketolase, phosphoglucose isomerase, and fructose 6-phosphate kinase were studied in extracts of wintering poplar (Populus gelrica) xylem. The xylem of wintering poplar showed high levels of transketolase, glucose 6-phosphate, and 6-phosphogluconate dehydrogenases. On recommencement of growth, the two dehydrogenase activities decreased. The three remaining enzymes appeared to be unchanged. In spring and early summer, glucose 6-phosphate dehydrogenase of the xylem was extremely low. On the other hand, 6-phosphogluconate dehydrogenase, which also became lower during the metabolic shift from winter to spring, was readily detected, and was several times higher than glucose 6-phosphate dehydrogenase throughout the year. The low dehydrogenase activities lasted into late October and then appeared to resume their original activity. A shift of metabolism at the beginning of growth was also observed by measuring the amount of sugar phosphates, soluble amino acids and amides, and proteins in the xylem. In contrast to the decrease of the two dehydrogenases and soluble proteins at the time of budding, incorporation of lysine-U-¹⁴C into the xylem protein ramained constant. A method to transfuse radioactive compounds into a section of stem was described.     

Comparative profiles of the hexose monophosphate dehydrogenases in rat tissues over the lactation cycle

The mammary gland tissue hexose monophosphate dehydrogenase activities were low in virgin, pregnant and weaned rats, but increased at the onset of lactation. The muscle and liver glucose 6-phosphate dehydrogenase activity peaked at early and late lactation respectively. The liver 6-phosphogluconate dehydrogenase peaked in late pregnancy and remained elevated through lactation. The muscle 6-phosphogluconate dehydrogenase peaked at the onset of lactation. The adipose tissue hexose monophosphate dehydrogenases exhibited small changes during pregnancy and lactation. The spleen hexose monophosphate dehydrogenases did not respond to lactation An overshoot in both the liver and the adipose tissue hexose monophosphate dehydrogenases was observed on weaning. Serum glucose levels remained unchanged throughout pregnancy, lactation and weaning. Only liver glucose 6-phosphate dehydrogenase activity correlated with plasma insulin, which also correlated positively with food consumption. The results demonstrate that tissue-specific control of the hexose monophosphate dehydrogenases occurs in the female rat during its complete lactation cycle.     

Importance of medullary events in ammonium excretion: studies in acute respiratory and acute metabolic acidosis

The renal medulla can play an important role in acid excretion by modulating both hydrogen ion secretion in the medullary collecting duct and the medullary PNH3. The purpose of these experiments was to characterize the intrarenal events associated with ammonium excretion in acute acidosis. Cortical events were monitored in two ways: first, the rates of glutamine extraction and ammoniagenesis were assessed by measuring arteriovenous differences and the rate of renal blood flow; second, the biochemical response of the ammoniagenesis pathway was examined by measuring glutamate and 2-oxoglutarate, key renal cortical metabolites in this pathway. There were no significant differences noted in any of these cortical parameters between acute respiratory and metabolic acidosis. Despite a comparable twofold rise in ammonium excretion in both cases, the urine pH, PNH3, and the urine minus blood PCO2 difference (U-B PCO2) were lower during acute hypercapnia. In these experiments, the urine PCO2 was 34 mmHg (1 mmHg = 133.322 Pa) lower than that of the blood during acute respiratory acidosis while the U-B PCO2 was 5 +/- 3 mmHg in acute metabolic acidosis. Thus there were significant differences in medullary events during these two conditions. Although the urine pH is critical in determining ammonium excretion in certain circumstances, these results suggest that regional variations in the medullary PNH3 can modify this relationship.     

Enzyme activities in human breast tumours.

The activities of six enzymes associated with carbohydrate metabolism were measured both in carcinomas and in normal breast tissues. The following differences were observed. 1. The carcinoma showed higher enzyme activities than the normal mammary tissue. 2. The ratios of glutamate dehydrogenase, hydroxybutyrate dehydrogenase, glutathione reductase and catalase to lactate dehydrogenase were lower in carcinomas than in normal tissues. Similarly, the ratios of glutamate dehydrogenase, hydroxybutyrate dehydrogenase, glutathione reductase and catalase to glucose-6-phosphate dehydrogenase were also significantly lower in carcinomas. 3. There were no significant differences in enzyme activities between I and II stage of the disease and the metastatic tissues, however, there were significant differences between I and III stage. The significance of these findings is discussed in terms of the alterations in the balance between the metabolic pathways.     

Electrophoretic studies of several dehydrogenases in relation to the cold tolerance of alfalfa.

Two cultivars of alfalfa (Medicago sativa L.), cold-tolerant Vernal and cold-sensitive Sonora, were grown under summer, winter, and dehardening conditions to determine the solubility characteristics and relationships of several dehydrogenases to cold tolerance.Soluble enzymatic proteins, extracted with three extractants, from lyophilized crown and root tissues, were separated by polyacrylamide disc gel electrophoresis.Gels assayed for glutamate, NAD-malate, NADP-malate, isocitrate, lactate, 6-phosphogluconate, and glucose-6-phosphate dehydrogenases showed quantitative differences in isoenzymes that were influenced by cultivar, extractant, and environmental differences.For both cultivars, enzyme activity was lowest during summer, increased in winter, and decreased during dehardening. Dehydrogenase activity, therefore, was closely associated with the fluctuations in soluble protein concentration, which were related to environmental changes and cold tolerance.Additional isoenzymes of isocitrate, lactate, and glucose-6-phosphate dehydrogenases were detected in the winter samples of both cultivars; however, most of the qualitative differences observed were generally due to the differential solubilities of isoenzymes in the three extractants.Comparison of data obtained from the use of frozen and unfrozen extracts indicated differential stabilities of the dehydrogenases to freezing in the different extractants. Glutamate, NAD-malate, and NADP-malate dehydrogenases were fairly stable to freezing whereas isocitrate, lactate, 6-phosphogluconate, and glucose-6-phosphate dehydrogenases were labile. Detectable levels of the latter dehydrogenases in frozen extracts were evident only in certain extracts of winter samples, indicating the importance of the nature of the extraction medium in protecting against enzyme denaturation.Since both cultivars showed similar changes in dehydrogenase activities at most times, the increased enzyme levels during winter coincided with increased levels of soluble protein and soluble sugars, which are indicative of the broad spectrum of metabolic changes involved in the attainment of the cold-tolerant state.     

A comparative histochemical evaluation of various dehydrogenases in the oral squamous epithelium

Summary A histochemical observation was made of various dehydrogenase activities in oral squamous epithelia. The localization of dehydrogenases showed a relatively similiarity except for the intensity of the dehydrogenase activity. Succinic dehydrogenase activity was generally confined to the basal cell layer and adjacent cell layers; superficial layers did not show any enzymatic activity. Lactic, and malic dehydrogenase activities were localized in the basal cells to st. granulosum, and the activity of lactic dehydrogenase was the highest. -Glycerophosphate, glutamic, glucose-6-phosphate and TPN-isocitric dehydrogenase activities were observed in all the epithelial cells with the exception for the hornified layer, and they were found generally low. -Hydroxybutyric dehydrogenase was low and contained in both of st. germinativum and st. granulosum, the keratohyalin in st. granulosum being occasionally found reactive to this enzymatic activity.In connective tissue cells and collagen bundels, activities of lactic, and malic dehydrogenase were intense, while other dehydrogenases were low or trace amount.In the oral squamous epithelium under normal conditions, the dehydrogenase localization concerning the glucose metabolism and TCA cycle member and other close pathways was not similar. Nor were their activities found likewise. Those findings lead to a conclusion that the epithelial cells of the same layer many show a selective metabolic activity.With 21 Figures in the Text     

Histochemical localization of primary and secondary alcohol dehydrogenases in whole-body, freeze-dried sections of mice

Summary Whole-body sagittal sections of frozen, C57BL/6J, adult, male mice were used for the localization of primary and secondary alcohol dehydrogenases in most tissues of the body. The reduction of Nitro BT with NAD⁺ as coenzyme, as described originally by Hardonk (1965), was utilized for the generation of coloured final reaction deposits. Ethanol was used as a substrate for primary alcohol dehydrogenase; 2-propanol, -methylbenzyl alcohol and 2-butanol were used as substrates for secondary alcohol dehydrogenase. Liver and bronchial epithelium showed the highest activities for both enzymes; oesophageal and upper gastric epithelium showed a high activity of primary alcohol dehydrogenase. Pyrazole, indazole and imidazole inhibited primary, but not secondary, alcohol dehydrogenase. Dimethylsulphoxide and menthol slightly inhibited both enzymes. Oleic acid, sulphydryl agents,p-chloromercuribenzoate, and copper sulphate also inhibited both enzymes. Slight inhibition of secondary dehydrogenase was observed on co-administration of several alcohols.As expected,N-nitrosonornicotine did not function as a substrate for alcohol dehydrogenases. When this compound was present in the histochemical incubation media, no activity was seen at any of the usual sites of these enzymes. The distribution of the alcohol dehydrogenase activities found in this study correlates with the distribution of radioactivity in oesophagus, bronchi and liver after administration of [¹⁴C]nitrosonornicotine. This suggests that the alcohol dehydrogenases may be involved in the metabolism of hydroxylated nitrosonornicotine, a metabolite of the most abundant known carcinogen in cigarette smoke.     

Dehydrogenases of the pentose phosphate pathway in rat liver peroxisomes

Subcellular distribution of pentose-phosphate cycle enzymes in rat liver was investigated, using differential and isopycnic centrifugation. The activities of the NADP+-dependent dehydrogenases of the pentose-phosphate pathway (glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase) were detected in the purified peroxisomal fraction as well as in the cytosol. Both dehydrogenases were localized in the peroxisomal matrix. Chronic administration of the hypolipidemic drug clofibrate (ethyl-alpha-p-chlorophenoxyisobutyrate) caused a 1.5-2.5-fold increase in the amount of glucose-6-phosphate and phosphogluconate dehydrogenases in the purified peroxisomes. Clofibrate decreased the phosphogluconate dehydrogenase, but did not alter glucose-6-phosphate dehydrogenase activity in the cytosolic fraction. The results obtained indicate that the enzymes of the non-oxidative segment of the pentose cycle (transketolase, transaldolase, triosephosphate isomerase and glucose-phosphate isomerase) are present only in a soluble form in the cytosol, but not in the peroxisomes or other particles, and that ionogenic interaction of the enzymes with the mitochondrial and other membranes takes place during homogenization of the tissue in 0.25 M sucrose. Similar to catalase, glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase are present in the intact peroxisomes in a latent form. The enzymes have Km values for their substrates in the millimolar range (0.2 mM for glucose-6-phosphate and 0.10-0.12 mM for 6-phosphogluconate). NADP+, but not NAD+, serves as a coenzyme for both enzymes. Glucose-6-phosphate dehydrogenase was inhibited by palmitoyl-CoA, and to a lesser extent by NADPH. Peroxisomal glucose-6-phosphate and phosphogluconate dehydrogenases have molecular mass of 280 kDa and 96 kDa, respectively. The putative functional role of pentose-phosphate cycle dehydrogenases in rat liver peroxisomes is discussed.     

Enzyme histochemistry of the sheep uterus during the oestrous cycle

Enzyme histochemical techniques were applied to frozen sheep uteri from different stages of the oestrous cycle. The localization and activities of succinate, lactate, glucose-6-phosphate, and isocitrate (NADP+) dehydrogenases and acid and alkaline phosphatases were studied in the luminal and glandular epithelia, caruncle and myometrium. Enzyme activity in the sections was scored on a scale of 0--5. In general the enzyme activity in the uterine caruncles and epithelia was higher than in the myometrium. The myometrium did not show any alkaline phosphatase activity and isocitrate dehydrogenase (NADP+) activity was negligible. The low activities of acid phosphatase and lactate dehydrogenase and the moderate levels of glucose-6-phosphate and succinate dehydrogenases in the myometrium were constant. The caruncular tissue showed high levels of phosphatases and glucose-6-phosphate dehydrogenase, moderate levels of lactate and succinate dehydrogenases, and low levels of isocitrate dehydrogenase (NADP+) throughout the oestrous cycle. Much lower phosphatase and isocitrate dehydrogenase (NADP+) levels were found in the epithelium of deep glands compared with superficial glands. The high activity of acid and alkaline phosphatases in the luminal epithelium and the superficial glands was constant from mid-cycle to ovulation, but a significant decrease was observed immediately after ovulation. The level of dehydrogenases in epithelia was generally high and did not change during the oestrous cycle.     

Glycogen metabloism in the developing chick glycogen body: functional significance of the direct oxidative pathway.

Glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and glucose-6-phosphatase were quantitatively determined for the first time in glycogen body tissue from late embryonic and neonatal chicks. For comparative purposes, the activities of these enzymes were examined also in liver and skeletal muscle from pre- and post-hatched chicks. The present data show that both the embryonic and neonatal glycogen body lack glucose-6-phosphatase, but contain relatively high levels of glucose-6-phosphate dehydrogenase. The activity of each dehydrogenase in either embryonic or neonatal glycogen body tissue is two- to five-fold greater than that found in muscle or liver from pre- or post-hatched chicks. The relatively high activities observed for both dehydrogenases in the glycogen body, together with the absence of glucose-6-phosphatase activity in that tissue, suggest that the direct oxidative pathway (pentose phosphate cycle) of glucose metabolism is a functionally significant route for glycogen utilization in the glycogen body. It is hypothesized that the glycogen body is metabolically linked to lipid synthesis and myelin formation in the central nervous system of the avian embryo.     

Metabolic zonation in teleost gastrointestinal tract

Activities of several metabolic enzymes show distinct patterns of zonation along the intestinal tract of tilapia (Oreochromis niloticus), rainbow trout (Oncorhynchus mykiss) and copper rockfish (Sebastes caurinus). Zonation is species and enzyme specific, with different metabolic activities concentrated in specific areas, and few generalizations can be made. The rockfish show the smallest degree of zonation, with highest activities in the third quarter of the intestine, and shallow gradients to either side, and a general upswing in activity towards the distal end. In the trout, mitochondrial enzyme activities (citrate synthase, glutamate dehydrogenase, malate dehydrogenase) are highest in the pyloric caeca and decrease along the length of the small intestine. This pattern is accentuated for malic enzyme and glucose 6-phosphate dehydrogenase. These enzymes drop precipitously in activity after the first few sections of the small intestine, while other NADP-linked dehydrogenases (isocitrate dehydrogenase, and 6-phosphogluconate dehydrogenase) show moderate activity in pyloric caeca and peak toward the distal section of the small intestine. In tilapia, glutamate dehydrogenase shows a similar decrease as in trout, but citrate synthase peaks towards the distal sections. NADP-dependent dehydrogenases reveal distinct patterns, peaking in different sections of the intestine-malic enzyme in the proximal midsection, glucose 6-phosphate dehydrogenase in the distal mid-section, and isocitrate dehydrogenase in the anal section. Enzyme activities in the stomach of trout and tilapia also show zonation, with the midsection generally displaying the highest activities. A 5-day treatment of tilapia with an intraperitoneal cortisol deposit (25 mg kg(-1) wet mass) drastically alters metabolic performance along the gut in enzyme specific patterns, generally increasing enzyme activities in site-specific arrangements. Cortisol treatment also leads to the expected increases in activities of phosphoenolpyruvate carboxykinase, pyruvate kinase and aspartate aminotransferase in liver, but not in kidney. Aspartate aminotransferase is the only enzyme in brain significantly increased by cortisol treatment. Short-term food deprivation changes enzyme patterns, often resembling those observed after cortisol administration. We conclude that brain, liver and intestinal amino acid metabolism is an important target for cortisol action in fish and that metabolic zonation is a key factor to be reckoned with when analyzing physiological phenomena in the fish intestine.     

Inhibition of glutamine synthetase in the mouse kidney: a novel mechanism of adaptation to metabolic acidosis

As part of a study on the regulation of renal ammoniagenesis in the mouse kidney, we investigated the effect of chronic metabolic acidosis on glutamine synthesis by isolated mouse renal proximal tubules. The results obtained reveal that, in tubules from control mice, glutamine synthesis occurred at high rates from glutamate and proline and, to a lesser extent, from ornithine, alanine, and aspartate. A 48 h, metabolic acidosis caused a marked inhibition of glutamine synthesis from near-physiological concentrations of both alanine and proline that were avidly metabolized by the tubules; metabolic acidosis also greatly stimulated glutamine utilization and metabolism. These effects were accompanied by a large increase (i) in alanine, proline, and glutamine gluconeogenesis and (ii) in ammonia accumulation from proline and glutamine. In the renal cortex of acidotic mice, the activity of phosphoenolpyruvate carboxykinase increased 4-fold, but that of glutamate dehydrogenase did not change; in contrast with what is known in the rat renal cortex, metabolic acidosis markedly diminished the glutamine synthetase activity and protein level, but not the glutamine synthetase mRNA level in the mouse renal cortex. These results strongly suggest that, in the mouse kidney, glutamine synthetase is an important regulatory component of the availability of the ammonium ions to be excreted for defending systemic acid-base balance. Furthermore, they show that, in rodents, the regulation of renal glutamine synthetase is species-specific.     

Sex differences in the control of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. Interaction of estrogen, testosterone and insulin in the regulation of enzyme levels in vivo and in cultured hepatocytes

Control of the activities of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and malate dehydrogenase was investigated in intact rats and in hepatocyte cultures. 1) Adult females had 2-fold greater activities of hepatic glucose-6-phosphate- and 6-phosphogluconate dehydrogenases than adult males, but similar activities of malate dehydrogenase. Castrated males showed decreased activities of all three enzymes in comparison to age- and weight-matched intact controls. In starved animals the activities of all three enzymes decreased significantly. After refeeding with nonpurified diet the activities returned to the prestarved levels in females, but increased to clearly higher values in intact and castrated males. 2) Estrogen levels were in the same range in immature and adult male and female rats. Testosterone levels were highest in adult males, clearly lower in adult females (1/8) and immature males (1/8), still lower in immature females (1/15) and lowest in castrated males (1/40). A simple correlation of the sex differences in these hormone levels to sex differences in glucose-6-phosphate- and 6-phosphogluconate dehydrogenase activities was not apparent. 3) In serum-free, dexamethasone-supplemented 48-h cultures of hepatocytes from both male and female rats the basal activities of glucose-6-phosphate dehydrogenase were the same; they were increased 2-3 fold by insulin alone, 1.5 fold by estrogen alone and 4-5 fold by insulin plus estrogen. Apparently sex differences did not persist in 48-h cell cultures. 4) In 48-h cultures of male hepatocytes, then used as the experimental model, insulin alone increased the activity not only of glucose-6-phosphate dehydrogenase but also of 6-phosphogluconate and malate dehydrogenases.(ABSTRACT TRUNCATED AT 250 WORDS)     

Enzyme levels in cultured astrocytes,oligodendrocytes and Schwann cells,and neurons from the cerebral cortex and superior cervical ganglia of the rat

Data are presented for 16 enzymes from 8 metabolic systems in cell cultures consisting of approximately 95% astrocytes and 5% oligodendrocytes. Nine of these enzymes were also measured in cultures of oligodendrocytes, Schwann cells, and neurons prepared from both cerebral cortex and superior cervical ganglia. Activities, in mature astrocyte cultures, expressed as percentage of their activity in brain, ranged from 9% for glycerol-3-phosphate dehydrogenase to over 300% for glucose-6-phosphate dehydrogenase. Creatine phosphokinase activity in astrocytes was about the same as in brain, half as high in oligodendrocytes, but 7% or less of the brain level in Schwann cells and superior cervical ganglion neurons and only 16% of brain in cortical neurons. Three enzymes which generate NADPH, the dehydrogenases for glucose-6-phosphate and 6-phosphogluconate, and the NADP-requiring isocitrate dehydrogenase, were present in astrocytes at levels at least twice that of brain. Oligodendrocytes had enzyme levels only 30% to 70% of those of astrocytes. Schwann cells had much higher lactate dehydrogenase and 6-phosphogluconate dehydrogenase activities than oligodendrocytes, but showed a remarkable similarity in enzyme pattern to those of cortical and superior cervical ganglion neurons.Special issue dedicated to Dr. Lewis Sokoloff.     

The influence of lipogenic and lipolytic conditions on the pentose phosphate pathway dehydrogenases in rat-kidney-cortex.

The effects of various lipogenic and antilipogenic states on the activities of rat-kidney cortex glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase have been studied. These conditions are related to the long-term administration of different diets, such as high-carbohydrate (80%) and high-fat (23%), and also to a state of fast. Contrary to what happens in liver cells and kidney cortex during a high protein diet administration, none of these nutritional conditions produced significant changes in the kinetics of either kidney hexose monophosphate dehydrogenases.