Hypothyroidism leads to a decreased expression of mitochondrial F0F1-ATP synthase in rat liver

Hesperidin Attenuates Hypothyroidism-Induced Lung Damage in Adult Albino Rats by Modulating Oxidative Stress, Nuclear Factor Kappa-B Pathway, Proliferating Cell Nuclear Antigen and Inflammatory Cytokines

The occurrence of worsening pulmonary function has been connected to hypothyroidism (HPO). Hesperidin (HES) was suggested to have antioxidant, anti-proliferative, and anti-inflammatory potential. Our study's objective was to determine whether HES could reduce carbimazole (CBZ)-induced lung injury more effectively than Eltroxin (ELT) in adult male albino rats or not. At random, 32 rats were distributed into four groups: Group I: normal control, to induce HPO, the remaining three groups were given CBZ (20 mg/kg/day) dissolved in distilled water for 1 week. They were then split up into three groups. Group II: orally administered CBZ (20 mg/kg b.w in water/day), Group III: HES (200 mg/kg/day) dissolved in 1% carboxymethyl-cellulose + CBZ treated, and Group IV: ELT (0.045 mg/kg/day) dissolved in distilled water + CBZ treated. All treatments were delivered for 12 weeks. Blood was collected to assess thyroid-stimulating hormone (TSH) and thyroid hormones (THs). Lung injury was evaluated based on the pulmonary content of interleukin (IL)-35, IL-6, and tumor necrosis factor-alpha (TNF-α), along with the estimation of lipid peroxidation, catalase, glutathione levels, superoxide dismutase, heme oxygenase-1 (HO-1), and nuclear factor erythroid 2-related factor 2 (Nrf2). The histological, ultrastructural, and immunohistochemical study of nuclear factor Kappa-B (NF-κB) and inducible nitric oxide synthase (iNOS), together with estimating the proliferation of cells using Antigen Ki-67 in lung tissue were performed. HES and ELT primarily suppressed variable lung damage mechanisms by suppressing TSH, the NF-κB/TNF-α pathway, iNOS, lipid peroxidation, Ki-67, and inflammatory mediators. On the other hand, they improved THs, antioxidant parameters, and the Nrf2/HO-1 pathway. HES and ELT exhibited an ameliorative effect that was reflected in the histopathological, immunohistochemical, and ultrastructural results. These results indicate that HES is a pneumoprotective agent that could be a promising treatment for oxidative stress, inflammation, and proliferation.

In vitro and in vivo activation of mitochondrial membrane permeability transition pore using triiodothyronine

Using a novel method for evaluating mitochondrial swelling (Drahota et al. 2012a) we studied the effect of calcium (Ca(2+)), phosphate (P(i)), and triiodothyronine (T(3)) on the opening of mitochondrial membrane permeability transition pore and how they interact in the activation of swelling process. We found that 0.1 mM P(i), 50 microM Ca(2+) and 25 microM T(3) when added separately increase the swelling rate to about 10 % of maximal values when all three factors are applied simultaneously. Our findings document that under experimental conditions in which Ca(2+) and P(i) are used as activating factors, the addition of T(3) doubled the rate of swelling. T(3) has also an activating effect on mitochondrial membrane potential. The T(3) activating effect was also found after in vivo application of T(3). Our data thus demonstrate that T(3) has an important role in opening the mitochondrial membrane permeability pore and activates the function of the two key physiological swelling inducers, calcium and phosphate ions.

Supplementation of T3 recovers hypothyroid rat liver cells from oxidatively damaged inner mitochondrial membrane leading to apoptosis

Hypothyroidism is a growing medical concern. There are conflicting reports regarding the mechanism of oxidative stress in hypothyroidism. Mitochondrial oxidative stress is pivotal to thyroid dysfunction. The present study aimed to delineate the effects of hepatic inner mitochondrial membrane dysfunction as a consequence of 6-n-propyl-2-thiouracil-induced hypothyroidism in rats. Increased oxidative stress predominance in the submitochondrial particles (SMP) and altered antioxidant defenses in the mitochondrial matrix fraction correlated with hepatocyte apoptosis. In order to check whether the effects caused by hypothyroidism are reversed by T₃, the above parameters were evaluated in a subset of T₃-treated hypothyroid rats. Complex I activity was inhibited in hypothyroid SMP, whereas T₃ supplementation upregulated electron transport chain complexes. Higher mitochondrial H₂O₂ levels in hypothyroidism due to reduced matrix GPx activity culminated in severe oxidative damage to membrane lipids. SMP and matrix proteins were stabilised in hypothyroidism but exhibited increased carbonylation after T₃ administration. Glutathione content was higher in both. Hepatocyte apoptosis was evident in hypothyroid liver sections; T₃ administration, on the other hand, exerted antiapoptotic and proproliferative effects. Hence, thyroid hormone level critically regulates functional integrity of hepatic mitochondria; hypothyroidism injures mitochondrial membrane lipids leading to hepatocyte apoptosis, which is substantially recovered upon T₃ supplementation.

3,5-Diiodo-L-thyronine administration to hypothyroid rats rapidly enhances fatty acid oxidation rate and bioenergetic parameters in liver cells

Growing evidence shows that, among triiodothyronine derivatives, 3,5 diiodo-L-thyronine (T(2)) plays an important role in energy metabolism and fat storage. In the present study, short-term effects of T(2) administration to hypothyroid rats on fatty acid oxidation rate and bioenergetic parameters were investigated. Within 1 h following T(2) injection, state 3 and state 4 respiration rates, which were reduced in hypothyroid mitochondria, were noticeably increased particularly in succinate- with respect to glutamate/malate-energized mitochondria. Maximal respiratory activity, observed when glutamate/malate/succinate were simultaneously present in the respiratory medium, was significantly stimulated by T(2) treatment. A T(2)-induced increase in respiratory rates was also observed when palmitoyl-CoA or L-palmitoylcarnitine were used as substrates. No significant change in respiratory control index and ADP/O ratio was observed. The activities of the mitochondrial respiratory chain complexes, especially Complex II, were increased in T(2)-treated rats. In the latter, Complex V activities, assayed in both ATP synthesis and hydrolysis direction, were enhanced. The rate of fatty acid oxidation, followed by conversion of [(14)C]palmitate to CO(2) and ketone bodies, was higher in hepatocytes isolated from T(2)-treated rats. This increase occurs in parallel with the raise in the activity of carnitine palmitoyltransferase-I, the rate limiting enzyme of fatty acid β-oxidation, assayed in situ in digitonin-permeabilized hepatocytes. Overall, these results indicate that T(2) rapidly increases the ability of mitochondria to import and oxidize fatty acids. An emerging idea in the literature is the ability of T(2) to reduce adiposity and dyslipidemia and to prevent the development in liver steatosis. The results of the present study, showing a rapid T(2)-induced increase in the ability of mitochondria to import and oxidize fatty acids, may contribute to understand the biochemical mechanisms of T(2)-metabolic effects.

Differential Expression ESTs Associated with Fluorosis in Rats Liver

The fluoride has volcanic activity and abundantly exists in environment combining with other elements as fluoride compounds. Recent researches indicated that the molecular mechanisms of intracellular fluoride toxicity were very complex. However, the molecular mechanisms underlying the effects on gene expression of chronic fluoride-induced damage is unknown, especially the detailed regulatory process of mitochondria. In the present study, we screened the differential expression ESTs associated with fluorosis by DDRT-PCR in rat liver. We gained 8 genes, 3 new ESTs, and 1 unknown function sequence and firstly demonstrated that microsomal glutathione S-transferase 1 (MGST1), ATP synthase H⁺ transporting mitochondrial F₀ complex subunit C1, selenoprotein S, mitochondrial IF1 protein, and mitochondrial succinyl-CoA synthetase alpha subunit were participated in mitochondria metabolism, functional and structural damage process caused by chronic fluorosis. This information will be very helpful for understanding the molecular mechanisms of fluorosis.

3,5-diiodo-L-thyronine increases FoF1-ATP synthase activity and cardiolipin level in liver mitochondria of hypothyroid rats

Short-term effects of 3,5-L-diiodothyronine (T(2)) administration to hypothyroid rats on F(o)F(1)-ATP synthase activity were investigated in liver mitochondria. One hour after T(2) injection, state 4 and state 3 respiration rates were noticeably stimulated in mitochondria subsequently isolated. F(o)F(1)-ATP synthase activity, which was reduced in mitochondria from hypothyroid rats as compared to mitochondria from euthyroid rats, was significantly increased by T(2) administration in both the ATP-synthesis and hydrolysis direction. No change in β-subunit mRNA accumulation and protein amount of the α-β subunit of F(o)F(1)-ATP synthase was found, ruling out a T(2) genomic effect. In T(2)-treated rats, changes in the composition of mitochondrial phospholipids were observed, cardiolipin (CL) showing the greatest alteration. In mitochondria isolated from hypothyroid rats the decrease in the amount of CL was accompanied by an increase in the level of peroxidised CL. T(2) administration to hypothyroid rats enhanced the level of CL and decreased the amount of peroxidised CL in subsequently isolated mitochondria, tending to restore the CL value to the euthyroid level. Minor T(2)-induced changes in mitochondrial fatty acid composition were detected. Overall, the enhanced F(o)F(1)-ATP synthase activity observed following injection of T(2) to hypothyroid rats may be ascribed, at least in part, to an increased level of mitochondrial CL associated with decreased peroxidation of CL.

Methyl-beta-cyclodextrin induces mitochondrial cholesterol depletion and alters the mitochondrial structure and bioenergetics

There is growing evidence of mitochondrial membrane raft-like microdomains that are involved in the apoptotic pathway. The aim of this study was to investigate the effect of methyl-beta-cyclodextrin (MβCD), being a well-known lipid microdomain disrupting agent and cholesterol chelator, on the structure and bioenergetics of rat liver mitochondria (RLM). We observed that MβCD decreases the function of RLM, induces changes in the mitochondrial configuration state and decreases the calcium chloride-induced swelling. These data suggest that disruption of mitochondrial raft-like microdomains by cholesterol efflux on one hand impairs mitochondrial bioenergetics, but on the other hand it protects the mitochondria from swelling.

T3 fails to restore mitochondrial thiol redox status altered by experimental hypothyroidism in rat testis

Oxidative stress impaired sperm function might lead to infertility. The objective of this study was to evaluate the effects of altered thyroid hormone levels on regulation of mitochondrial glutathione redox status and its dependent antioxidant defense system in adult rat testis and their correlation with testicular function. Adult male Wistar rats were rendered hypothyroid by administration of 6-n-propyl-2-thiouracil in drinking water for six weeks. At the end of the treatment period, a subset of the hypothyroid rats was treated with T(3) (20 μg/100g body weight/day for 3 days). Mitochondria were isolated from euthyroid, hypothyroid and hypothyroid+T(3)-treated rat testes, and sub-fractionated into sub-mitochondrial particles and matrix fractions. Mitochondrial respiration, oxidative stress indices and antioxidant defenses were assayed. The results were correlated with daily testicular sperm production and epididymal sperm viability. Increased pro-oxidant level and reduced antioxidant capacity rendered the hypothyroid mitochondria susceptible to oxidative injury. The extent of damage was more evident in the membrane fraction. This was reflected in higher degree of oxidative damages inflicted upon membrane lipids and proteins. While membrane proteins were more susceptible to carbonylation, thiol residue damage was evident in matrix fraction. Reduced levels of glutathione and ascorbate further weakened the antioxidant defenses and impaired testicular function. Hypothyroid condition disturbed intra-mitochondrial thiol redox status leading to testicular dysfunction. Hypothyroidism-induced oxidative stress condition could not be reversed with T(3) treatment.

Adenine nucleotide translocator promotes oxidative phosphorylation and mild uncoupling in mitochondria after dexamethasone treatment

The composition of the mitochondrial inner membrane and uncoupling protein [such as adenine nucleotide translocator (ANT)] contents are the main factors involved in the energy-wasting proton leak. This leak is increased by glucocorticoid treatment under nonphosphorylating conditions. The aim of this study was to investigate mechanisms involved in glucocorticoid-induced proton leak and to evaluate the consequences in more physiological conditions (between states 4 and 3). Isolated liver mitochondria, obtained from dexamethasone-treated rats (1.5 mg.kg(-1).day(-1)), were studied by polarography, Western blotting, and high-performance thin-layer chromatography. We confirmed that dexamethasone treatment in rats induces a proton leak in state 4 that is associated with an increased ANT content, although without any change in membrane surface or lipid composition. Between states 4 and 3, dexamethasone stimulates ATP synthesis by increasing both the mitochondrial ANT and F1-F0 ATP synthase content. In conclusion, dexamethasone increases mitochondrial capacity to generate ATP by modifying ANT and ATP synthase. The side effect is an increased leak in nonphosphorylating conditions.

Comparative study of myocardial high energy phosphate substrate content in slow and fast growing chicken and in chickens with heart failure and ascites

In order to explain the biochemical mechanisms associated with deteriorating heart function in broiler chickens, this study compared myocardial high energy phosphate substrates in leghorns, feed restricted (Broilers-Res) broilers, ad libitum fed broilers (Broilers-AL), and in broilers that developed heart failure and ascites. The profile of adenine nucleotide content in the heart tissue did not differ between leghorns and Broilers-Res, but there were significant differences among Broilers-Res, Broilers-AL, and broilers with ascites. During intensive growth periods, leghorns and Broilers-Res showed increasing trends in heart ATP levels, whereas in fast growing broilers the heart ATP declined (p<0.021). ATP:ADP and ATP:CrP ratios increased with age in both leghorn and Broilers-Res, declined in fast growing broilers, and were the lowest in broilers that developed heart failure. The changes in heart high energy phosphate profile in broilers suggest that the energy demand of the heart during a rapid growth phase may exceed the bird's metabolic capacity to supply adequate levels of high energy phosphate substrate. The insufficiency of energy substrate likely contributes to the declining heart rate. In some individuals this may lead to impaired heart pump function, and in more severe cases may progress to heart pump failure.

Evidence that triiodothyronine decreases rat serum leptin concentration by down-regulation of leptin gene expression in white adipose tissue

Conflicting results have been reported regarding the effect of triiodothyronine (T(3)) on serum leptin and adipose tissue leptin gene expression in human and animals. The aim of the present study was to evaluate the effect of administration of increasing doses of T(3) on serum leptin concentration and on leptin mRNA abundance in white adipose tissue of rats. The results presented in this paper indicate that administration of single different doses of T(3) to euthyroid rats resulted dose dependent increases of serum total T(3) concentrations which are associated with a decrease in white adipose tissue leptin mRNA level. The leptin mRNA level in white adipose tissue was negatively correlated with serum total T(3) concentration (r=-0.8, p<0.001). Like white adipose tissue leptin mRNA level, serum leptin concentration decreased after T(3) administration, and was also negatively correlated with the serum T(3) concentration (r=-0.8, p<0.001). In contrast, administration of T(3) to the same rats led to a significant increase in white adipose tissue expression of the malic enzyme gene (malic enzyme activity and malic enzyme mRNA level), a known target gene for T(3). The results indicate that T(3) exerts a selective inhibitory effect on white adipose tissue leptin gene expression in vivo. A conclusion is that T(3) decreases rat serum leptin concentration by down-regulation of leptin gene expression in white adipose tissue.

Hypothyroidism down-regulates mitochondrial citrate carrier activity and expression in rat liver

The effect of hypothyroidism on citrate carrier (CiC) activity has been investigated in rat-liver mitochondria. The rate of citrate transport was reduced by approximately 50% in mitochondria from hypothyroid as compared with euthyroid rats. In parallel, a decrease in the rate of de novo fatty acid synthesis was observed in the cytosol of the former animals. Kinetic analysis of citrate transport revealed that only the Vmax was reduced by hypothyroidism, while Km was almost unaffected. Hypothyroidism increased the mitochondrial percentage of phosphatidylcholine while decreased that of phosphatidylethanolamine; an altered fatty acid pattern but no significant difference in the sum of saturated and unsaturated fatty acids as well as in the unsaturation index was observed. The CiC Arrhenius plot did not show appreciable difference between the two groups of rats. However, Western blot analysis associated with mRNA quantitation indicated that both protein level and mRNA accumulation of hepatic CiC were noticeably decreased in hypothyroid state. Therefore, a reduced content of the carrier protein can represent a plausible mechanism to explain the decline in the CiC activity observed in rat liver mitochondria of hypothyroid rats.

Time-course of hormonal induction of mitochondrial glycerophosphate dehydrogenase biogenesis in rat liver

Thyroid hormones are important regulators of mitochondrial metabolism. Due to their complex mechanism of action, the timescale of different responses varies from minutes to days. In this work, we studied selective T3 induction of the inner mitochondrial membrane enzyme-glycerophosphate dehydrogenase (mGPDH) in liver of euthyroid rats. We correlated the kinetics of the T3 level in blood, the mRNA level in liver, the activity and amount of mGPDH in liver mitochondria after a single dose of T3. The T3 level reached maximum after 1 h (80 nmol/l) and subsequently rapidly decreased. mGPDH mRNA increased also relatively fast, reaching a maximum after 12 h and fell to the control level after 72 h. An increase of mGPDH activity could be already found after 6 h and reached a maximum after 24 h in accordance with the increase in mGPDH content (2.4-fold vs. 2.7-fold induction). After 72 h, the mGPDH activity showed a significant 30% decrease. When the rats received three subsequent doses of T3, the increase of mGPDH activity was 2-fold higher than after a single T3 dose. The results demonstrate that mGPDH displays rapid induction as well as decay upon disappearance of a hormonal stimulus, indicating a rather short half-life of this inner mitochondrial membrane enzyme.

The reduced tolerance of rat fatty liver to ischemia reperfusion is associated with mitochondrial oxidative injury

BACKGROUND

Oxidative stress contributes to the pathogenesis of hepatic ischemia-reperfusion injury. This study aimed to determine whether fatty degeneration affects the oxidative damage during warm ischemia reperfusion and whether mitochondria, the major intracellular site of energy synthesis, represent a preferential target of this injury.

MATERIALS AND METHODS

Fed rats with control or fatty liver induced by choline deficiency underwent 60' lobar ischemia and reperfusion. Oxidative damage was assessed by measuring in whole liver tissue and in isolated mitochondria the thiobarbituric acid-reactive substances (TBARs), protein carbonyls (PC), and total and oxidized glutathione (GSH and GSSG) concentrations. The mitochondrial F0-F1-ATPase content and the oxidative phosphorylation activity were also determined. Rat survival and ALT release were assessed as parameters of liver injury.

RESULTS

In the whole liver tissue, with the exception of TBARs, no differences were observed for GSH, GSSG, and PC between the two groups throughout all of the experiment. In contrast, in isolated mitochondria, fatty infiltration was associated with a mild oxidative imbalance already under basal conditions. The preischemic differences in the mitochondrial TBARs, PC, and GSSG levels were significantly amplified by reperfusion in the presence of steatosis. The enhanced oxidative damage was associated to a reduced F0-F1-ATPase content and oxidative phosphorylation activity in fatty liver mitochondria. Finally, serum ALT levels were significantly greater and survival significantly lower in rats with steatotic liver.

CONCLUSIONS

Fatty infiltration exacerbates mitochondrial oxidative injury during warm ischemia reperfusion. The increased oxidative stress can alter mitochondrial functions, including key processes for ATP synthesis, thus, contributing to the reduced tolerance to reperfusion injury.

Thyroid hormone treatment of hypothyroid rats restores the regenerative capacity and the mitochondrial membrane permeability properties of the liver after partial hepatectomy

We have investigated the effect of thyroid hormone on recovery of liver mass and on the mitochondrial membrane permeability properties during rat liver regeneration after 70% partial hepatectomy (PH). In the euthyroid state, liver weight starts to recover 24 h after PH and is completely restored 96 h after PH. Cyclosporin A (CsA)-sensitive mitochondrial permeability transition (MPT) occurs 24 h after PH, and it has been suggested to act in the signaling mechanism for hepatocyte proliferation. In this study we show that hypothyroidism delays recovery of the liver mass, being only 50% of the initial weight 96 h after PH, and alters the duration and mode of MPT occurrence, first inducing a CsA-insensitive swelling 24 h after PH, followed by a CsA-sensitive swelling 96 h after PH. The occurrence of both CsA-sensitive and -insensitive swelling is shown to be associated with an increase in mitochondrial calcium content. Concurrent with mitochondrial swelling, external release of matrix proteins from mitochondria, such as aspartate aminotransferase and malate dehydrogenase, is shown to be CsA insensitive 24 h after PH and CsA sensitive 96 h after PH. After thyroid hormone administration to hypothyroid rats, the liver regenerative capacity is restored, and the duration and mode of MPT occurrence as well as changes in mitochondrial calcium content become similar to those observed in the euthyroid condition. The results of the present study suggest the involvement of a mitochondria-mediated pathway in regulation of the liver regenerative process by thyroid hormone.

Mitochondrial glutathione content determines the rate of liver regeneration after partial hepatectomy in eu- and hypothyroid rats

BACKGROUND/AIMS

Mitochondrial glutathione has been postulated to affect mitochondrial function and liver regeneration.

METHODS

Mitochondrial respiration, total and oxidized glutathione, and liver regeneration were assessed after partial hepatectomy in glutathione-depleted and in hypothyroid rats with/without supplementation of glutathione ester.

RESULTS

Mitochondrial, cytosolic and circulating glutathione levels were lower in glutathione-depleted rats. Hepatectomy was followed by significant changes of intra- and extracellular glutathione and of mitochondrial respiration. In glutathione-deficient rats, the recovery of mitochondrial function and the liver regeneration were delayed. Administration of glutathione ester partially corrected the fall of cytosolic and mitochondrial glutathione following hepatectomy, reduced mitochondrial oxidative damage, and accelerated the restoration of mitochondrial respiration and the rate of liver regeneration. In hypothyroid rats, intracellular glutathione homeostasis and mitochondrial respiration were impaired already at baseline; slower regeneration and mitochondrial oxidative alterations were observed after hepatectomy. Glutathione ester ameliorated the regenerative response in hypothyroid rats by providing higher concentrations of cytosolic and mitochondrial glutathione.

CONCLUSIONS

Glutathione depletion and hypothyroidism affect the mitochondrial function during liver regeneration. Liver regenerates more slowly in glutathione-depleted and in hypothyroid rats. The earlier restoration of mitochondrial function and the higher rate of proliferation in glutathione ester treated rats suggest that the maintenance of intracellular glutathione facilitates liver regeneration.

Thyroid hormone administration to hypothyroid rats restores the mitochondrial membrane permeability properties

We have investigated the effect of thyroid hormone on the mitochondrial membrane permeability properties in a hypothyroid rat model. The role played by calcium in affecting these properties has been also examined. Cyclosporin A-sensitive mitochondrial calcium efflux, swelling, and external release of matrix proteins are events that occur normally during the permeability transition process induced by calcium loading of mitochondria. We demonstrate that these events are impaired in mitochondria isolated from the liver of hypothyroid rats, even in the presence of high calcium content. However, after thyroid hormone administration to hypothyroid rats, the mitochondrial permeability transition process in response to calcium loading is restored. Consequently, mitochondrial calcium efflux, swelling, and release of matrix proteins, like glutamate dehydrogenase, malate dehydrogenase, and aspartate aminotransferase occur. These effects are abrogated by the concomitant administration of cyclosporin A. The results of the present study suggest that hypothyroidism may be a potential source of adverse effects in patients receiving cyclosporin A.

Thyroid hormone increases transcription of GA-binding protein/nuclear respiratory factor-2 alpha-subunit in rat liver

Thyroid hormone (TH) regulates mitochondrial respiratory rate by activating coordinated transcription in the nucleus and mitochondria. Whereas TH activates transcription of mitochondrial genes directly, the activation of nuclear-encoded mitochondrial genes is probably executed by indirect unknown mechanisms. Nuclear respiratory factors (NRF)-1 and GA-binding protein (BP)/NRF-2 may function as transacting genes, but regulation of these genes by TH is not demonstrated. We show that TH administration to hypothyroid rats promptly increases GABP/NRF-2 alpha-subunit mRNA levels in the liver, without significant changes in beta, gamma subunits. In run-on and time-course experiments, the transcription rate and protein levels increased three-fold in response to TH, indicating GABP/NRF-2 transcriptional regulation. The results also support the notion that ATP synthase beta-subunit is regulated by TH through the indirect activation of GABP/NRF-2.

The influence of hypoxia on the myocardium of experimentally diabetic rats with and without protection by Ginkgo biloba extract. III: Ultrastructural investigations on mitochondria

Completing our preceding ultrastructural studies on diabetes and additional acute hypoxia of rat myocardium and the protective effect of Ginkgo extract (EGb) we investigated specific ultrastructural-morphometric parameters of corresponding mitochondria. Aim of the study was to answer the question whether mitochondria of diabetic myocardium are more sensitive to hypoxia than in normal condition, and whether antioxidative protection by EGb is effective. Further we compared the ultrastructural reactions of mitochondria of different intracellular locations. Voluminal parameters of mitochondria indicated a moderate swelling after diabetes and a further slight swelling after additional hypoxia, which was slightly reduced after EGb pretreatment. Decrease of volume density of mitochondrial cristae was less expressed after diabetes and much stronger after additional hypoxia; slight protection by EGb was only visible after diabetes. Degenerative intramitochondrial areas increased significantly after diabetes and after hypoxia; EGb was protective only after additional hypoxia. The relative number of ATPase particles (F1-coupling factors) at the inner mitochondrial membranes was slightly but significantly reduced after diabetes and stronger reduced after additional hypoxia; only in the latter condition Ginkgo extract was slightly protective. The product of volume density of mitochondria x volume density of cristae x relative number of ATPase particles at the inner mitochondrial membrane (as structural equivalent of the myocardial capacity for ATP production) indicated better than single parameters the increasing mitochondrial damage after diabetes of 4 months duration and subsequent acute hypoxia of 20 min duration. After hypoxia this capacity amounted only to 46% of the normal and was improved by EGb to 53%.

Correlation between decreased expression of mitochondrial F0F1-ATP synthase and low regenerating capability of the liver after partial hepatectomy in hypothyroid rats

In hypothyroid rats, partial hepatectomy does not induce liver regeneration until 120 h after surgical operation. when, instead, in normal rats a complete recovery of the liver mass, in this interval, is observed. In normal rats, a good efficiency of mitochondrial oxidative phosphorylation is needed as an energy source for liver regeneration (Guerrieri, F. et al., 1995); in hypothyroid rats the efficiency of mitochondrial oxidative phosphorylation is low in the 0-120 h interval after partial hepatectomy. This low efficiency of oxidative phosphorylation appears to be related to a low mitochondrial content of F0F1-ATP synthase, in liver of hypothyroid rats, which does not recover after partial hepatectomy. In the liver of hypothyroid rats, low levels of the nuclear-encoded mitochondrial catalytic betaF1 subunit and of its transcript are observed and they do not increase, as occurs in normal rats, after partial hepatectomy.