Α-glycerophosphate Dehydrogenase Activity Research Articles

Mitochondrial Disorders in Stroke and Chronic Brain Ischemia

Stroke is the leading cause of disability and death in the adult population. Modern methods of treating patients with acute ischemic stroke include thrombolytic therapy with a narrow therapeutic window and endovascular thrombectomy. The development of other methods of treatment of brain hypoxia in the penumbra zone is relevant. Mitochondria, which are involved in immediate and delayed molecular mechanisms of adaptation to hypoxic stress in the cerebral cortex, primarily respond to hypoxia. Hypoxia induces reprogramming of the mitochondrial respiratory chain function and switching from oxidation of substrates of the respiratory chain complex I to succinate oxidation (complex II). The brain's need for succinate increases. Clinical studies have shown a positive effect of drugs containing succinates on the course of stroke. The study of mitochondrial function is carried out mainly in an experiment. In the present study of mitochondrial disorders in stroke and chronic brain ischemia in adult patients, the quantitative method proposed by A. G. Pearse was used to assess the activity of mitochondrial enzymes of peripheral blood lymphocytes, which are referred to as the enematic mirror of tissues. In acute cerebral ischemia, a compensatory increase in the activity of succinate dehydrogenase was observed on the first day, indicating the tension (increased activity) of the second complex of the mitochondrial respiratory chain.. These data confirm the need to prescribe succinic acid in the acute phase of stroke. At the same time, the dose of 250 mg per day is not sufficient for patients with increased body weight. The standard dose of the drug should be higher, taking into account the different body weight of patients. In patients with stroke, there was also a decrease in the activity of α-glycerophosphate dehydrogenase, which is involved in the fat metabolism of mitochondria, which is an indication for the appointment of carnitine. In chronic brain ischemia, the activity of succinate dehydrogenase and α-glycerophosphate dehydrogenase decreased, indicating indications for the appointment of idebenone and carnitine along with vasodilator therapy and endovascular thrombectomy. Thus, the results of a study of mitochondrial function in patients with acute and chronic brain ischemia are presented. Violations of complex II in the respiratory chain cycle and violation of fat metabolism were revealed, indicating indications for the appointment of energotropic therapy.

Дистальный артрогрипоз 5-го типа – артрогрипоз с офтальмоплегией, полиневропатией. Клинический случай

A clinical case of a 27-year-old patient with distal arthrogryposis of the 5th type – arthrogryposis with ophthalmoplegia, which was combined in a patient with polyneuropathy is presented. To assess tissue respiration (mitochondrial respiratory chain) and other types of metabolism in mitochondria, cytochemical analysis of lymphocytes in peripheral blood was carried out according to A. Pearse's method modified by R.P. Narcissov. The activity of four mitochondrial enzymes involved in carbohydrate metabolism (lactate dehydrogenase), amino acid metabolism (glutamate dehydrogenase), fatty acid metabolism (α-glycerophosphate dehydrogenase) and the second complex of the mitochondrial respiratory chain (succinate dehydrogenase) was assessed. A slight decrease in the activity of the enzyme succinate dehydrogenase, which is part of the second complex of the mitochondrial respiratory chain, was determined. The activity of the enzyme α-glycerophosphate dehydrogenase was more significantly reduced, an increase in the activity of lactate dehydrogenase was noted. In the presented observation, along with the typical manifestations of the disease (contractures of the hands and feet, ophthalmoplegia, ptosis of the eyelids, visual impairment), polyneuropathy with impaired sensitivity of the polyneuritic type was revealed. Thus, a patient with polyneuropathy had a hereditary type 5 arthrogryposis disease. Along with the typical manifestations of the disease, polyneuropathy with hyporeflexia and impaired sensitivity of the polyneuritic type was revealed. Secondary mitochondrial disorders were identified, which was the basis for the appointment of energotropic therapy.

Experimental substantiation of the possibility of using the cytochemical parameters of peripheral blood to assess the functional state of the organism of the pilot

The activity of succinate (mitochondrial), lactate, α-glycerophosphate, glucose-6-phosphate peripheral blood lymphocytes in rats under the conditions of modeling acute and chronic gravitational stress was studied by quantitative spectrophotometry of cytochemical reaction products to reveal the localization of oxidative enzymes. The dynamics of morphofunctional transformations is determined, the severity of which depends on the duration of the effect (the rotation time of the animals on the centrifuge). For acute gravitational stress, changes in the activity of mitochondrial succinate dehydrogenase are characteristic, and in the various stages of chronic gravitational stress, glycolysis (increase in lactate dehydrogenase and α-glycerophosphate dehydrogenase activity) and plastic metabolism (increase in glucose-6-fosfata dehydrogenase activity) are characteristic. These changes are explained by the inclusion of neurohumoral regulatory mechanisms that ensure synchronization of oxidative metabolic processes in the cells of organs of various body systems under unfavorable conditions of their functioning. Significant correlation links between the activity of lymphocyte enzymes with the same indices of neurons of the celiac sympathetic node, adenocytes of the cortical and medulla of the adrenal glands have been established. This suggests that the activity of lymphocyte enzymes can be used as indirect indicators of the processes occurring in the organs of the sipato-adrenomedular and pituitary-adrenocortical systems under conditions of acute and chronic gravitational stress.

НЕКОТОРЫЕ ПОКАЗАТЕЛИ МОРФОФУНКЦИОНАЛЬНОЙ АКТИВНОСТИ ЛИМФОЦИТОВ ПЕРИФЕРИЧЕСКОЙ КРОВИ У ЖЕНЩИН С ОСЛОЖНЕННЫМ ТЕЧЕНИЕМ БЕРЕМЕННОСТИ

The aim of the research was to study some indices of morphofunctional state of lymphocytes in the peripheral blood under a complicated course of pregnancy in women of Khabarovsk. 96 women were examined in different trimesters of gestation. Two main groups depending on the type of complications were formed: the first group consisted of pregnant women with vaginitis, the second group had women whose pregnancy was complicated with clinical manifestations in the form of edemas, proteinuria and hypertensive disorders. The group of comparison included the women without complications. In the peripheral blood of the women under study with the method of high tech automated digital system of blood smear test VISION HEMA there was done a morphometric assessment of lymphocytes and with histochemical methods there was found a level of fermentation activity of succinate dehydrogenase (SDH), α-glycerophosphate dehydrogenase (α-GPDH) and lactate dehydrogenase (LDH). By morphometric studies of lymphocytes of the peripheral blood in pregnant women of the first group in the III trimester of gestation the indices of the square of the cell, of cytoplasm, cytoplasm brightness, the square of the nucleus and the brightness of the nucleus were 102.33±9.83 mсm², 36.84±4.88 mсm², 181.39±6.94 units of optical density, 65.69±6.87 mсm², 97.44±6.88 units of optical density, respectively (in the group of the comparison these data were 121.31±4.44 mсm²; 46.14±2.52 mсm²; 167.74±3.44 units of optical density; 75.33±2.66 mkm², 88.00±3.36 units of optical density, respectively). In the second group of women the same data in the same period of pregnancy corresponded to the following values: 128.44±4.89 mсm², 57.15±3.87 mсm², 173.53±4.65 units of optical density, 70.95±3.39 mсm² and 91.13±4.93 units of optical density (in the group of comparison there were the following data: 109.92±3.57 mсm², 39.63±1.53 mсm², 158.96±2.63 units of optical density, 75.37±3.23 mсm², 82.16±2.58 units of optical density, respectively). By the results of histochemical studies the level of activity of enzymes SDH, α-GPDH, LDH in the first group of pregnancy was 15.38±2.10, 10.72±0.58 and 20.53±2.36 pellet/cell, respectively. And just the other way round in pregnant women of the second group there was revealed a statistically reliable suppression of fermentation activity of these enzymes: 9.11±0.75 (p<0.05); 9.61±1.06 (p>0.05); 8.31±1.20 (p<0.05) pellet/cell in regard to the data in the group of comparison (12.84±1.21; 12.18±1.13 and 13.09±0.78 pellet/cell, respectively). Thus the changes of morphometric indices characterizing parameters of the cell, the nucleus and lymphocytes cytoplasm in a complex study with their fermentation activity can be extra diagnostic criteria of the formation of different complications during pregnancy. The obtained data allow to justify in-time application of medications for the correction of metabolic disorders of immune competent cells with the aim to decrease unfavorable perinatal outcomes.

Resveratrol supplementation does not augment performance adaptations or fibre-type-specific responses to high-intensity interval training in humans.

The present study examined the effect of concurrent exercise training and daily resveratrol (RSV) supplementation (150 mg) on training-induced adaptations following low-dose high-intensity interval training (HIIT). Sixteen recreationally active (∼22 years, ∼51 mL·kg(-1)·min(-1)) men were randomly assigned in a double-blind fashion to either the RSV or placebo group with both groups performing 4 weeks of HIIT 3 days per week. Before and after training, participants had a resting muscle biopsy taken, completed a peak oxygen uptake test, a Wingate test, and a submaximal exercise test. A main effect of training (p < 0.05) and interaction effect (p < 0.05) on peak aerobic power was observed; post hoc pairwise comparisons revealed that a significant (p < 0.05) increase occurred in the placebo group only. Main effects of training (p < 0.05) were observed for both peak oxygen uptake (placebo - pretraining: 51.3 ± 1.8, post-training: 54.5 ± 1.5 mL·kg(-1)·min(-1), effect size (ES) = 0.93; RSV - pretraining: 49.6 ± 2.2, post-training: 52.3 ± 2.5 mL·kg(-1)·min(-1), ES = 0.50) and Wingate peak power (placebo: pretraining: 747 ± 39, post-training: 809 ± 31 W, ES = 0.84; RSV - pretraining: 679 ± 39, post-training: 691 ± 43 W, ES = 0.12). Fibre-type distribution was unchanged, while a main effect of training (p < 0.05) was observed for succinate dehydrogenase activity and glycogen content, but not α-glycerophosphate dehydrogenase activity or intramuscular lipids in type I and IIA fibres. The fold change in PGC-1α, SIRT1, and SOD2 gene expression following training was significantly (p < 0.05) lower in the RSV group than placebo. These results suggest that concurrent exercise training and RSV supplementation may alter the normal training response induced by low-volume HIIT.

Rapid Determination of Myosin Heavy Chain Expression in Rat, Mouse, and Human Skeletal Muscle Using Multicolor Immunofluorescence Analysis

Skeletal muscle is a heterogeneous tissue comprised of fibers with different morphological, functional, and metabolic properties. Different muscles contain varying proportions of fiber types; therefore, accurate identification is important. A number of histochemical methods are used to determine muscle fiber type; however, these techniques have several disadvantages. Immunofluorescence analysis is a sensitive method that allows for simultaneous evaluation of multiple MHC isoforms on a large number of fibers on a single cross-section, and offers a more precise means of identifying fiber types. In this investigation we characterized pure and hybrid fiber type distribution in 10 rat and 10 mouse skeletal muscles, as well as human vastus lateralis (VL) using multicolor immunofluorescence analysis. In addition, we determined fiber type-specific cross-sectional area (CSA), succinate dehydrogenase (SDH) activity, and α-glycerophosphate dehydrogenase (GPD) activity. Using this procedure we were able to easily identify pure and hybrid fiber populations in rat, mouse, and human muscle. Hybrid fibers were identified in all species and made up a significant portion of the total population in some rat and mouse muscles. For example, rat mixed gastrocnemius (MG) contained 12.2% hybrid fibers whereas mouse white tibialis anterior (WTA) contained 12.1% hybrid fibers. Collectively, we outline a simple and time-efficient method for determining MHC expression in skeletal muscle of multiple species. In addition, we provide a useful resource of the pure and hybrid fiber type distribution, fiber CSA, and relative fiber type-specific SDH and GPD activity in a number of rat and mouse muscles.

Letters to the Editor

Letters to the Editor

Prolactin inhibition at the end of lactation programs for a central hypothyroidism in adult rat

Malnutrition during lactation is associated with hypoprolactinemia and failure in milk production. Adult rats whose mothers were malnourished presented higher body weight and serum tri-iodothyronine (T(3)). Maternal hypoprolactinemia at the end of lactation caused higher body weight in adult life, suggesting an association between maternal prolactin (PRL) level and programming of the offspring's adult body weight. Here, we studied the consequences of the maternal PRL inhibition at the end of lactation by bromocriptine (BRO) injection, a dopaminergic agonist, upon serum TSH and thyroid hormones, thyroid iodide uptake, liver mitochondrial alpha-glycerophosphate dehydrogenase (mGPD), liver and pituitary de-iodinase activities (D1 and/or D2), and in vitro post-TRH TSH release in the adult offspring. Wistar lactating rats were divided into BRO - injected with 1 mg/twice a day, daily for the last 3 days of lactation, and C - control, saline-injected with the same frequency. At 180 days of age, the offspring were injected with (125)I i.p. and after 2 h, they were killed. Adult animals whose mothers were treated with BRO at the end of lactation presented lower serum TSH (-51%), T(3) (-23%), and thyroxine (-21%), lower thyroid (125)I uptake (-41%), liver mGPD (-55%), and pituitary D2 (-51%) activities, without changes in the in vitro post-TRH TSH release. We show that maternal PRL suppression at the end of lactation programs a hypometabolic state in adulthood, in part due to a thyroid hypofunction, caused by a central hypothyroidism, probably due to decreased TRH secretion. We suggest that PRL during lactation can regulate the hypothalamus-pituitary-thyroid axis and programs its function.

Skeletal muscle bioenergetics: a comparative study of mitochondria isolated from pigeon pectoralis, rat soleus, rat biceps brachii, pig biceps femoris and human quadriceps

The metabolism of mitochondria isolated from five functionally different skeletal muscles is compared. Data for a single ectothermic preparation are also reported. The mitochondria were prepared in yields of 44±7% from 50 to 100 mg muscle. The muscle content of mitochondrial protein ranged between 2 and 40 g kg −1. Twelve specific activities of key enzymes and metabolic systems were determined, 10 of these in functional assays with respiratory measurements. The specific activities of glutamate dehydrogenase, α-glycerophosphate dehydrogenase, and exo-NADH oxidase differed considerably among muscle sources. Seven specific activities, including very central reactions, showed low among-muscle variation. The activity of ATP synthesis, for instance, was 1.0–1.3 mmol min −1 g −1 mitochondrial protein, 25 °C. In vitro data were extrapolated to in vivo conditions of the muscles. The calculated rates of respiration and ATP synthesis were in accordance with reported tissue activities. Pigeon pectoralis mitochondria showed a unique cytochrome spectrum and a respiratory chain activity that might effect simultaneous carbohydrate and fatty acid respiration. In mitochondria from the other muscles, the respiratory chain activity balanced the carbohydrate oxidation capacity. In all muscles, the respiratory capacity exceeds that needed for oxidative phosphorylation. This may secure maximal mitochondrial ATP synthesis during maximal work rates and high cellular [Ca 2+].

Marrow stromal cell recovery after radiation-induced aplasia in mice

Purpose : The identification of fibroblast-like cells of the marrow stroma by means of alkaline phosphatase (ALP) cytochemistry reveals delicate ALP-positive structures interspersed among haematopoietic cells and arranged in a loosely meshed network. These cells are often referred to as 'reticular' cells and the network they form is known as the 'ALP network'. The purpose was to analyse the evolution of this ALP network in relation to haemopoietic regeneration after whole-body irradiation. Materials and methods : The total surface occupied by ALP-positive processes revealed by means of ALP cytochemistry was expressed as a ratio of the total marrow area. ALP-positive cells were counted using nuclei as the defining unit. Cell proliferation was analysed by the detection of bromodeoxyuridine (BrdU) incorporation. Fat cells were identified by oil red O staining and α-glycerophosphate dehydrogenase (α-GPDH) activity. Results : The ALP network and ALP-positive cell number began to increase 24 h after 4-Gy irradiation to reach a maximum after 72 h, when the bone marrow was almost completely empty of haemopoietic cells. This increase was in advance of haemopoietic recovery and was not due to cell proliferation. A decrease in the ALP network occurred in parallel with an increase in haemopoiesis and was accompanied by a transient increase in fat cells on day 7. Conclusions : These data indicate that the recovery of the ALP network, which is partially due to the recruitment of ALP- positive cells, occurs in advance of the haemopoietic recovery and that the equilibrium between fat cells and ALP-positive cells seems to be controlled by haemopoietic cells.

Vitamin B 12-induced alterations in activities of α-glycerophosphate dehydrogenase and malic enzyme in brain of singi fish, Heteropneustes fossilis (Bloch)

Different doses of vitamin B 12 (0.25, 0.5, 1, 2 and 4 μg/g, injected intraperitoneally for three consecutive days) altered the activities of mitochondrial-α-glycerophosphate dehydrogenase (α-GPD) and NADP-dependent cytosolic malic enzyme (ME) in the brain of singi fish. The α-GPD activity increased at doses of 0.5, 1, 2 and 4 μg/g vitamin B 12. A dose of 0.5 μg/g vitamin B 12 induced less activity than higher doses. ME activity increased with 1, 2 and 4 μg/g of vitamin B 12/g. The mitochondrial and cytosolic protein content remained unchanged after vitamin B 12 administration. Cycloheximide treatment inhibited the vitamin B 12-induced increase in α-GPD and ME activity. Thus, vitamin B 12 is involved in the induction of some enzymes in fish brain.

Influence of complete spinal cord injury on skeletal muscle within 6 mo of injury

This study examined the influence of spinal cord injury (SCI) on affected skeletal muscle. The right vastus lateralis muscle was biopsied in 12 patients as soon as they were clinically stable (average 6 wk after SCI), and 11 and 24 wk after injury. Samples were also taken from nine able-bodied controls at two time points 18 wk apart. Surface electrical stimulation (ES) was applied to the left quadriceps femoris muscle to assess fatigue at these same time intervals. Biopsies were analyzed for fiber type percent and cross-sectional area (CSA), fiber type-specific succinic dehydrogenase (SDH) and alpha-glycerophosphate dehydrogenase (GPDH) activities, and myosin heavy chain percent. Controls showed no change in any variable over time. Patients showed 27-56% atrophy (P = 0.000) of type I, IIa, and IIax+IIx fibers from 6 to 24 wk after injury, resulting in fiber CSA approximately one-third that of controls. Their fiber type specific SDH and GPDH activities increased (P </= 0.001) from 32 to 90% over the 18 wk, thereby approaching or surpassing control values. The relative CSA of type I fibers and percentage of myosin heavy chain type I did not change. There was apparent conversion among type II fiber subtypes; type IIa decreased and type IIax+IIx increased (P </= 0.012). Force loss during ES did not change over time for either group but was greater (P = 0.000) for SCI patients than for controls overall (27 vs. 9%). The results indicate that vastus lateralis muscle shows marked fiber atrophy, no change in the proportion of type I fibers, and a relative independence of metabolic enzyme levels from activation during the first 24 wk after clinically complete SCI. Over this time, quadriceps femoris muscle showed moderately greater force loss during ES in patients than in controls. It is suggested that the predominant response of mixed human skeletal muscle within 6 mo of SCI is loss of contractile protein. Therapeutic interventions could take advantage of this to increase muscle mass.

Changes in myocardial thyroid hormone metabolism and alpha-glycerophosphate dehydrogenase activity in rats deficient in iodine and selenium.

Weanling Wistar rats were fed on diets prepared from grain from areas deficient in I and Se where Keshan disease in endemic. Rats were divided into four groups, each of twelve rats, and received a diet supplemented with: I, Se, I + Se or nothing. At 8 weeks after weaning, myocardial alpha-glycerophosphate dehydrogenase (EC 1.1.1.8; alpha-GPD) activity and indices of Se and thyroid hormone status were determined. The group supplemented with iodine had increased plasma thyroxine levels. There was no difference in plasma triiodothyronine concentration between the groups but triiodothyronine levels in heart were reduced in the Se-supplemented group. Se supplementation increased myocardial glutathione peroxidase activity (EC 1.11.1.9) and the type I 5'-deiodinase (EC 3.8.1.4) activity in rat liver, but no type I 5'-deiodinase activity was detected in heart. alpha-GDP activity in heart was increased in group supplemented with Se, I or both. There was a significant relationship (P < 0.05) between myocardial alpha-GDP activity and plasma thyroxine levels but not between alpha-GDP and myocardial glutathione peroxidase activity. The results indicate that iodine may be more important than Se in energy metabolism in the myocardium, which may give a new insight for the study of the aetiology of Keshan disease in areas where foodstuffs are deficient in both Se and I.

Postnatal development and differentiation of myofibres in functionally diverse porcine skeletal muscles.

Marked changes in muscle function occur after birth, with the response being dependent on developmental stage. Therefore, postnatal cellular ontogeny of functionally distinct skeletal muscles was investigated in the pig, a large mammal born at a relatively advanced stage of development. Assessment of myofibre contractile (type I slow/type II fast) and metabolic (oxidative/glycolytic) properties at Days 0, 2, 5 and 14 revealed type-specific differences in hypertrophy and differentiation. Type I fibre proportions increased significantly in soleus and diaphragm, especially between Days 0 and 5, and rhomboideus showed a similar trend, but in longissimus there was a slight decrease during Days 0-2. Cytochrome oxidase activity was relatively high and similar among myofibres in all muscles at birth, and fibres with low activity were not detected until Day 5. In contrast with previous reports, glycolytic fibres were present in all muscles at birth; postnatal changes in alpha-glycerophosphate dehydrogenase activity were both muscle- and myofibre-specific. Hence, although myosin ATPase activity and metabolic properties of porcine myofibres are well developed at birth, they continue to mature postnatally. This suggests that postnatal muscle development can be modulated by extrinsic factors, even in mammals born at a relatively advanced stage of development.

Lack of Peroxisome Proliferation in Marmoset Liver Following Treatment with Ciprofibrate for 3 Years

Lack of Peroxisome Proliferation in Marmoset Liver Following Treatment with Ciprofibrate for 3 Years. Graham, M. J., Wilson, S. A., Winham, M. A., Spencer, A. J., Rees, J. A., Old, S. L., and Bonner, F. W. (1994). Fundam. Appl. Toxicol. 22, 58-64.The effect of treatment of marmosets with ciprofibrate for 3 years on activities of hepatic enzymes, hepatic histomorphology, and ultrastructure were investigated. Male and female marmosets were dosed with ciprofibrate (2, 10, and 20 mg/kg) by oral gavage once daily for 3 years. No effect on liver weight (adjusted for body weight) or liver morphology was observed. The activities of catalase, glutathione peroxidase, α-glycerophosphate dehydrogenase, benzphetamine N-demethylase, and ethoxyresorufin O-deethylase were unaffected by treatment with ciprofibrate. Activity of glutathione transferase was increased in the low dosage group but unaffected in the mid and high dosage groups. Modest increases in activities of peroxisomal β-oxidation (2.5-fold, maximal), carnitine acetyl transferase (1.7-fold, maximal), an carnitine palmitoyl transferase (2-fold, maximal) were observed. Cytochemical staining and quantitative image analysis failed to indicate any effect on peroxisomal number, size, or volume density. Similarly, there was no increase in lipofuscin deposition. This study provides data on the effects of a potent peroxisome proliferator on primate liver following a dosing period much greater than that used in previously published studies and is further evidence that the marmoset is relatively insensitive to the well-documented effects that ciprofibrate and other peroxisome proliferators have on rat liver.

Effects of thyroid hormones on mitochondrial oxygen consumption in brown adipose tissue and heart from cold-exposed hypothyroid rats.

The present work measured brown adipose tissue and heart mitochondrial oxygen consumption in hypothyroid rats treated with replacement doses of T3, T4 or T4 plus iopanoic acid and kept at 4 degrees C for 24 h. Heart oxygen consumption in normal, untreated hypothyroid and T4-treated hypothyroid rats was unaffected by cold exposure. In rats treated with T4 plus iopanoic acid, rates of oxygen consumption were normal in those maintained at 4 degrees C as well as in those kept at room temperature, despite serum T3 concentration being significantly decreased. The cold-exposed T3-treated hypothyroid rats showed a marked decrease in oxygen consumption (p less than 0.02) and alpha-glycerophosphate dehydrogenase activity, a T3-dependent enzyme. Mitochondrial oxygen consumption in brown fat from normal (p less than 0.01), T4 (p less than 0.02) and T4 plus iopanoic acid-treated (p less than 0.01) rats rose more than twofold in response to cold. In the T3-treated group, oxygen consumption at room temperature was higher (p less than 0.02) than in any other group at similar temperatures. However, the T3-treated group showed no changes in oxygen consumption in response to cold, perhaps because this group reached the maximal response at room temperature. The untreated and the T3-treated hypothyroid rats (both groups devoid of T4) did not survive at 4 degrees C unless T4 or several-fold replacement amounts of T3 were administered. The data demonstrate the crucial role of T4 in thermogenesis during cold exposure.

Effects of chronic ethanol feeding on rat liver mitochondrial energy metabolism

Chronic alcohol consumption is known to decrease hepatic mitochondrial respiration rate. It was shown here that the proton leak through the mitochondrial inner membrane was unaffected by chronic ethanol treatment. This indicates that changes in proton leak are not responsible for the alterations in respiration found in mitochondria isolated from ethanol-treated rats. Therefore, the lowered coupled respiration rate is solely due to a decrease in the activity of the electron transport chain. However, this alteration was oniy evident in coupled respiration (i.e. state 4) and was not apparent in uncoupied respiration. Thus, chronic ethanoi treatment decreases the activity of the mitochondrial electron transport chain components which bave control over coupled, but not uncoupled, respiration. Mitochondrial energy metabolism is regulated by thyroid hormone status. It was shown that the chronic alcohol treatment did not affect the circulating leveis of thyroxine. Furthermore, the activity of mitochondrial α-glycerophosphate dehydrogenase, which is strongly affected by thyroid hormones, was unaltered by alcohol treatment. Thus, the effects of ethanol treatment on mitochondria occur independently of changes in circulating thyroid hormone levels.

Triiodothyronine and insulin effects on malic enzyme in hypothyroid and diabetic rats

We examined the effects of T3 and insulin on the activity of hepatic mitochondrial alpha-glycerophosphate dehydrogenase and cytosolic malic enzyme in control, thyroidectomized, thyroidectomized food-restricted, and thyroidectomized diabetic rats. In the three untreated thyroidectomized groups, the decrease in hepatic nuclear T3 content was accompanied by a marked reduction in the levels of alpha-glycerophosphate dehydrogenase and malic enzyme activity. Although the levels of both enzymes were increased by a receptor-saturating dose of T3, the alpha-glycerophosphate dehydrogenase response in the thyroidectomized groups was almost identical to that in controls, whereas that of malic enzyme was reduced to 45-62% of control values. Insulin failed to stimulate the alpha-glycerophosphate dehydrogenase levels in untreated and T3-treated thyroidectomized groups, but caused an increase in malic enzyme activity by 79-130% in untreated thyroidectomized groups, and enhanced the activity of this enzyme to about twice that seen with T3 alone. These effects were independent of changes in nuclear T3 binding parameters. The data suggest that insulin may act on malic enzyme synthesis through its general stimulatory effect on protein synthesis, or by antagonizing factors that inhibit the induction of this enzyme.

Characterization of the hepatic responses to the short-term administration of ciprofibrate in several rat strains: Co-induction of microsomal cytochrome P-450 IVA1 and peroxisome proliferation

The influence of ciprofibrate, a potent oxyisobutyrate derivative, on several hepatic enzyme parameters was studied in five rat strains following a 14-day treatment period. Ciprofibrate-dependent hepatomegaly was observed at two dose levels (2 and 20 mg/kg) in all rat strains examined. A 10- to 15-fold induction in the 12-hydroxylation of lauric acid with a less marked 1.5- to 5-fold induction of 11-hydroxylation was observed in treated animals. This dose-dependent increase in fatty acid hydroxylase activity was associated with a maximal 10-fold increase in the specific content of cytochrome P-450 IVA1 isoenzyme apoprotein, as assessed immunochemically using an ELISA technique. The activities of the cytochrome P-450 I (IA1 and IA2) and II (IIB1 and IIB2) families, as measured by ethoxyresorufin- O-deethylase and benzphetamine- N-demethylase activities respectively, were decreased on treatment. In the mitochondria, monoamine oxidase activity was significantly decreased at the higher dose level whereas α-glycerophosphate dehydrogenase activity was elevated. Total carnitine acetyltransferase activity (mitochondrial and peroxisomal) and peroxisomal β-oxidation were markedly increased at both dose levels in all strains examined. Cytosolic glutatnione peroxidase activity, measured using both t-butylhydroperoxide and hydrogen peroxide as substrates, was decreased on treatment to approximately 50% of the control value. In treated animals, a marked increase in mRNA levels coding for cytochrome P-450 IVA1 and the peroxisomal bifunctional protein of the fatty acid β-oxidation spiral was observed. However, mRNA levels coding for glutatnione peroxidase appeared unchanged following ciprofibrate administration, in contrast to the above-noted decrease of glutathione peroxidase enzyme activity. Taken collectively, our results have further substantiated a close association between the induction of microsomal cytochrome P-450 IVA1, peroxisomal β-oxidation and total carnitine acetyltransferase activity in rat liver, and have formed a conceptual basis for the rationalization of the chronic toxicity of peroxisome proliferators in this species.

Stimulation of oxidative metabolism by thyroid hormones in an apodan amphibian, Gegenophis carnosus (Beddome)

Administration of different doses of l-thyroxine (T 4) and triiodo- l-thyronine (T 3) in vivo in G. carnosus stimulated the activities of cytochrome oxidase, α-glycerophosphate dehydrogenase (α-GPDH), succinate dehydrogenase (SDH), and Mg 2+ adenosine triphosphatase (Mg 2+ ATPase) and inhibited the activity of malate dehydrogenase (MDH). While a low dose of thiouracil administration produced a stimulatory effect on cytochrome oxidase and α-GPDH activities, a higher dose of thiouracil significantly inhibited the activities of cytochrome oxidase, α-GPDH, SDH, Mg 2+ ATPase, and MDH. Injection of T 4 or T 3 into thiouracil-treated animals significantly restored the stimulatory effect of thyroid hormones on oxidative enzyme activities. It is suggested that thyroid hormones in vivo increase and that thiouracil decreases the oxidative capacity of hepatic mitochondria of G. carnosus.