Subject(s)
Adipose Tissue, Brown/drug effects , Cadmium Chloride/toxicity , Cold Temperature , Mitochondria/drug effects , Adipose Tissue, Brown/physiology , Animals , Body Temperature Regulation/drug effects , Male , Mitochondria/metabolism , Oxygen Consumption , Rats , Rats, Wistar , Triiodothyronine/administration & dosageABSTRACT
In the present work, the effect "in vivo' of increasing doses of RU 38486 upon the hepatic mitochondrial function of diabetic rats has been studied. At the same time, the action of adrenalectomy and corticosterone restitution on this function were comparatively demonstrated. The parameters measured were oxygen consumption with the substrates: 3-hydroxybutyrate (HB), succinate (Suc) and malate-glutamate (Mal-glut) in intact liver mitochondria and the activities of 3-hydroxybutyrate dehydrogenase (HBD) and cytochrome c oxidase (Cyt.c oxid.) enzymes in broken liver mitochondria. The groups of animals studied were normal controls (N) and the following groups of diabetic rats: rats without any treatment (D), adrenalectomized rats (D+ADX), rats that were adrenalectomized and treated with corticosterone (D+ADX+C) and four groups treated with increasing oral doses of RU (in mg/kg body wt.), that is, 12.5 (D+RU1), 25.0 (D+RU2), 37.5 (D+RU3) and 50.0 (D+RU4). The results showed a tendency of increasing values of mitochondrial oxygen consumption in diabetic animals treated with RU. The favourable effect of increasing doses of RU on O2 consumption of diabetic rat liver mitochondria with each of the substrates showed a significant association as indicated by the values obtained for the correlation coefficients r (0.95, 0.97 and 0.99 according to the substrate HB, Succ or Mal-glut, respectively). Likewise, the correlation between the treatment with increasing doses of RU and the recovery of enzyme activities showed a significant dose-effect association with r 0.94 for HBD and r = 0.95 for Cyt.c oxid. Adrenalectomy showed a similar effect to treatment with the maximum dose of RU while corticosterone restitution gave measured values similar to those of the D group. In conclusion, the favourable, significant variation of the hepatic mitochondrial function of diabetic rats was demonstrated by the dose-dependent treatment with RU as seen by the correlation statistical study performed. At the same time, the pernicious effect that glucocorticoids exert upon such function in experimental diabetes was confirmed.
Subject(s)
Diabetes Mellitus, Experimental/metabolism , Hormone Antagonists/pharmacology , Mifepristone/pharmacology , Mitochondria, Liver/drug effects , Oxygen Consumption/drug effects , 3-Hydroxybutyric Acid , Adrenalectomy , Animals , Anti-Inflammatory Agents/pharmacology , Corticosterone/pharmacology , Diabetes Mellitus, Experimental/enzymology , Dose-Response Relationship, Drug , Electron Transport Complex IV/drug effects , Electron Transport Complex IV/metabolism , Female , Hydroxybutyrate Dehydrogenase/drug effects , Hydroxybutyrate Dehydrogenase/metabolism , Hydroxybutyrates/metabolism , Malates/metabolism , Mitochondria, Liver/enzymology , Mitochondria, Liver/metabolism , Oxygen Consumption/physiology , Rats , Succinates/metabolism , Succinic AcidABSTRACT
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.
Subject(s)
Adipose Tissue, Brown/metabolism , Adipose Tissue/metabolism , Cold Temperature , Hypothyroidism/metabolism , Mitochondria, Heart/metabolism , Mitochondria/metabolism , Myocardium/metabolism , Oxygen Consumption/drug effects , Thyroxine/pharmacology , Triiodothyronine/pharmacology , Adipose Tissue/ultrastructure , Adipose Tissue, Brown/ultrastructure , Animals , Body Temperature Regulation/drug effects , Body Temperature Regulation/physiology , Glycerolphosphate Dehydrogenase/metabolism , Hypothyroidism/pathology , Hypothyroidism/physiopathology , Iopanoic Acid/pharmacology , Male , Mitochondria/drug effects , Mitochondria/physiology , Mitochondria, Heart/drug effects , Mitochondria, Heart/physiology , Myocardium/ultrastructure , Organ Size , Oxygen Consumption/physiology , Radioimmunoassay , Rats , Rats, Inbred Strains , Thyroxine/metabolism , Triiodothyronine/metabolismABSTRACT
In the present work we studied, in female chronic diabetic rats the effect of either the parenteral administration of tamoxifen (TAM) (500 micrograms.kg-1.day-1) for 15 days or the ovariectomy upon the respiration and oscillatory behaviour of intact mitochondria and the activities of 3-hydroxybutyrate dehydrogenase (HBD) and cytochrome c oxidase (Cox) of disrupted liver mitochondria. The treatment with TAM as well as the ovariectomy of diabetic animals significantly increased the respiratory control (RC) and the state 3 (S3) of respiration of intact liver mitochondria with the three substrates assayed (3-hydroxybutyrate, malate-glutamate and succinate). Both treatments also lowered significantly the damped factors of the oscillatory variation of liver intact mitochondria of diabetic rats. Moreover, the two above-mentioned treatments restored the activities of HBD and Cox of liver disrupted mitochondria to normal values. The effect of estrogens at level of its receptors in the modulation of liver mitochondrial function and liver HBD and Cox activities in chronic diabetes is discussed.
Subject(s)
Diabetes Mellitus, Experimental/physiopathology , Mitochondria, Liver/enzymology , Mitochondria, Liver/physiology , Ovariectomy , Tamoxifen/pharmacology , Analysis of Variance , Animals , Diabetes Mellitus, Experimental/enzymology , Electron Transport Complex IV/metabolism , Estradiol/physiology , Female , Hydroxybutyrate Dehydrogenase/metabolism , Mitochondria, Liver/drug effects , Oxygen Consumption , RatsABSTRACT
The present work studied the effect of cold on oxygen consumption (OC) and alpha-glycerophosphate dehydrogenase activity (alpha-GPD) in heart mitochondria of hypothyroid rats (hypo) treated with T3, T4 or T4 plus Iopanoic Acid (IOP). 200 g male Wistar rats were made hypothyroid by 131I administration. Animals were injected s.c., in divided doses, for 10 days, with one of the following substances: T3, 300 ng/100 g BW/day; T4, 2 micrograms/100 g BW/day or T4 plus IOP, 5 mg/100 g BW/day, for 72 h preceding the experiment. One half of each group was housed in a cold room at 4 degrees C and the other at 22 degrees C, for 25 h, and thereafter decapitated. Heart mitochondria were isolated by routine methods. The OC was measured polarographically using L-malate, L-glutamate and malonate as substrates. Intramitochondrial alpha-GPD activity was measured by a microcolorimetric assay. The results from 16 or 20 rats/group (4 or 5 pools of 4 hearts each) were: In the rats kept at 22 degrees C the OC (in ng at. oxyg./min/mg prot.; State 3) in the hypo+T4 group was 69 +/- 10; in the rats treated with T4+IOP, 75 +/- 11 and in the hypo+T3, 102 +/- 5. When the animals were exposed to 4 degrees C no change was observed in the hypo+T4 and hypo+T4IOP groups. On the other hand, OC was significantly lower in the T3-treated animals (p less than 0.001, versus their controls at 22 degrees C). This group of rats did not survive when exposed to cold.(ABSTRACT TRUNCATED AT 250 WORDS)
Subject(s)
Cold Temperature , Glycerolphosphate Dehydrogenase/metabolism , Mitochondria, Heart/physiology , Oxygen Consumption/physiology , Adaptation, Physiological , Animals , Body Temperature Regulation , Hypothyroidism/drug therapy , Hypothyroidism/physiopathology , Male , Rats , Rats, Inbred Strains , Thyroid Hormones/therapeutic use , Triiodothyronine/administration & dosageABSTRACT
In the present work the effects of corticosterone restitution were examined in female rats with chronic streptozotocin (SZ)-induced diabetes upon intact liver mitochondrial function and the activities of 3-hydroxybutyrate dehydrogenase (HBD), succinate dehydrogenase (SD) and cytochrome c oxidase (Cox) of the ruptured organelle. The liver mitochondrial function was analyzed by the respiration and the osmotic oscillatory behaviour. Respiration was measured by polarographic method and both the state 3 of active respiration (S3) and the respiratory control (RC) were determined using the following substrates: 3-hydroxybutyrate, succinate and malate-glutamate. The oscillatory behaviour was measured using as parameters the damping factors (DF) which are the ratios of amplitudes of two consecutive peaks or troughs of the spectrophotometrical tracings of this phenomenon. A group of control normal rats (N) and the following three groups of diabetic rats were studied: controls (D), adrenalectomized (D + ADX) and adrenalectomized with corticosterone restitution (D + ADX + C). The results of mitochondrial respiration showed that the mean values of S3 and RC decreased with the three substrates in the group D + ADX + C compared with D + ADX group (p < 0.001). This group demonstrated a significant increase of S3 and RC values of the respiration compared with the D group. The oscillatory behaviour of liver mitochondria of D + ADX + C group demonstrated a significant increase in the DF of peaks and troughs compared with D + ADX group. The values of DF of the latter group were not significantly different from the N group. The behaviour of the enzymes activities of ruptured liver mitochondria were different for each enzyme in the different groups of treated rats. Thus, in the D + ADX + C group the mean value of the activity of HBD significantly decreased, that of the Cox increased (p < 0.02) and that of SD did not show any variation compared with the corresponding values of the D + ADX group. Likewise, the mean value of HBD activity in this latter group was similar to that of the N group and that of Cox activity was lesser (p < 0.01) than that of the D group. The conclusion is drawn that corticosterone has significant additional diabetogenic effects upon biochemical functions of liver mitochondria in the SZ-induced diabetic state which could occur through the hormone cellular receptors.
Subject(s)
Corticosterone/pharmacology , Electron Transport Complex IV/metabolism , Hydroxybutyrate Dehydrogenase/metabolism , Mitochondria, Liver/physiology , Succinate Dehydrogenase/metabolism , Adrenalectomy , Animals , Corticosterone/administration & dosage , Diabetes Mellitus, Experimental , Female , Mitochondria, Liver/enzymology , Oxygen Consumption/drug effects , RatsABSTRACT
El presente trabajo estudió el efecto del frío sobre el consumo del oxígeno (CO) y la actividad *-glicerofosfato deshidrogenasa (*-GPD) en mitocondria cardíaca de ratas hipotiroideas (hipo) tratadas con T3, T4 o T4 más Acido lopanoico (IOP). Se usaron ratas Wistar macho de 200g de peso hechas hipotiroideas con la administración de I. Los animales fueron inyectadoss s.c., en dosis divididas, por 10 días, con una de las siguientes sustancias: T3, 300 ng/100g peso/día; T4, 2 *g/100g peso/día o T4 más IOP, 5 mg/100g peso/día, por 72 hs. previas al experimento. Una mitad de cada grupo fue mantenida a 4ºC y el resto a 22ºC, por 24 hs., y logo decapitados. Se aislaron las mitocondrias de corazón por métodos de rutina. El CO se midió polarográficamente usando L-malato, L-glutamato y malonato como sustratos. La actividad mitocondrial *-GPD se medió por un método microcolorimétrico. Los resultados correspondientes a 16 o 20 ratas/grupo (4 o 5 "pooles" de 4 corazones cada uno) fueron los isguientes: En las ratas mantenidas a 22ºC el CO (en ng at. de oxíg./min/mg prot.; Estado 3) de las Hipo+T4 fue de 69 ñ 10; en el grupo tratado con T4+IOP fue de 75 ñ 11 y ... (AU)
Subject(s)
Rats , Animals , Male , Cold Temperature , Mitochondria, Heart/physiology , Oxygen Consumption/physiology , Glycerolphosphate Dehydrogenase/metabolism , Thyroid Hormones/therapeutic use , Triiodothyronine/administration & dosage , Hypothyroidism/physiopathology , Hypothyroidism/drug therapy , Body Temperature Regulation , Adaptation, Physiological , Rats, Inbred StrainsABSTRACT
The present work studied the effect of cold on oxygen consumption (OC) and alpha-glycerophosphate dehydrogenase activity (alpha-GPD) in heart mitochondria of hypothyroid rats (hypo) treated with T3, T4 or T4 plus Iopanoic Acid (IOP). 200 g male Wistar rats were made hypothyroid by 131I administration. Animals were injected s.c., in divided doses, for 10 days, with one of the following substances: T3, 300 ng/100 g BW/day; T4, 2 micrograms/100 g BW/day or T4 plus IOP, 5 mg/100 g BW/day, for 72 h preceding the experiment. One half of each group was housed in a cold room at 4 degrees C and the other at 22 degrees C, for 25 h, and thereafter decapitated. Heart mitochondria were isolated by routine methods. The OC was measured polarographically using L-malate, L-glutamate and malonate as substrates. Intramitochondrial alpha-GPD activity was measured by a microcolorimetric assay. The results from 16 or 20 rats/group (4 or 5 pools of 4 hearts each) were: In the rats kept at 22 degrees C the OC (in ng at. oxyg./min/mg prot.; State 3) in the hypo+T4 group was 69 +/- 10; in the rats treated with T4+IOP, 75 +/- 11 and in the hypo+T3, 102 +/- 5. When the animals were exposed to 4 degrees C no change was observed in the hypo+T4 and hypo+T4IOP groups. On the other hand, OC was significantly lower in the T3-treated animals (p less than 0.001, versus their controls at 22 degrees C). This group of rats did not survive when exposed to cold.(ABSTRACT TRUNCATED AT 250 WORDS)
ABSTRACT
In the present work the effects of corticosterone restitution were examined in female rats with chronic streptozotocin (SZ)-induced diabetes upon intact liver mitochondrial function and the activities of 3-hydroxybutyrate dehydrogenase (HBD), succinate dehydrogenase (SD) and cytochrome c oxidase (Cox) of the ruptured organelle. The liver mitochondrial function was analyzed by the respiration and the osmotic oscillatory behaviour. Respiration was measured by polarographic method and both the state 3 of active respiration (S3) and the respiratory control (RC) were determined using the following substrates: 3-hydroxybutyrate, succinate and malate-glutamate. The oscillatory behaviour was measured using as parameters the damping factors (DF) which are the ratios of amplitudes of two consecutive peaks or troughs of the spectrophotometrical tracings of this phenomenon. A group of control normal rats (N) and the following three groups of diabetic rats were studied: controls (D), adrenalectomized (D + ADX) and adrenalectomized with corticosterone restitution (D + ADX + C). The results of mitochondrial respiration showed that the mean values of S3 and RC decreased with the three substrates in the group D + ADX + C compared with D + ADX group (p < 0.001). This group demonstrated a significant increase of S3 and RC values of the respiration compared with the D group. The oscillatory behaviour of liver mitochondria of D + ADX + C group demonstrated a significant increase in the DF of peaks and troughs compared with D + ADX group. The values of DF of the latter group were not significantly different from the N group. The behaviour of the enzymes activities of ruptured liver mitochondria were different for each enzyme in the different groups of treated rats. Thus, in the D + ADX + C group the mean value of the activity of HBD significantly decreased, that of the Cox increased (p < 0.02) and that of SD did not show any variation compared with the corresponding values of the D + ADX group. Likewise, the mean value of HBD activity in this latter group was similar to that of the N group and that of Cox activity was lesser (p < 0.01) than that of the D group. The conclusion is drawn that corticosterone has significant additional diabetogenic effects upon biochemical functions of liver mitochondria in the SZ-induced diabetic state which could occur through the hormone cellular receptors.
ABSTRACT
In the present work the effects of corticosterone restitution were examined in female rats with chronic streptozotocin (SZ)-induced diabetes upon intact liver mitochondrial function and the activities of 3-hydroxybutyrate dehydrogenase (HBD), succinate dehydrogenase (SD) and cytochrome c oxidase (Cox) of the ruptured organelle. The liver mitochondrial function was analyzed by the respiration and the osmotic oscillatory behaviour. Respiration was measured by polarographic method and both the state 3 of active respiration (S3) and the respiratory control (RC) were determined using the following substrates: 3-hydroxybutyrate, succinate and malate-glutamate. The oscillatory behaviour was measured using as parameters the damping factors (DF) which are the ratios of amplitudes of two consecutive peaks or troughs of the spectrophotometrical tracings of this phenomenon. A group of control normal rats (N) and the following three groups of diabetic rats were studied: controls (D), adrenalectomized (D + ADX) and adrenalectomized with corticosterone restitution (D + ADX + C). The results of mitochondrial respiration showed that the mean values of S3 and RC decreased with the three substrates in the group D + ADX + C compared with D + ADX group (p < 0.001). This group demonstrated a significant increase of S3 and RC values of the respiration compared with the D group. The oscillatory behaviour of liver mitochondria of D + ADX + C group demonstrated a significant increase in the DF of peaks and troughs compared with D + ADX group. The values of DF of the latter group were not significantly different from the N group. The behaviour of the enzymes activities of ruptured liver mitochondria were different for each enzyme in the different groups of treated rats. Thus, in the D + ADX + C group the mean value of the activity of HBD significantly decreased, that of the Cox increased (p < 0.02) and that of SD did not show any variation compared with the corresponding values of the D + ADX group. Likewise, the mean value of HBD activity in this latter group was similar to that of the N group and that of Cox activity was lesser (p < 0.01) than that of the D group. The conclusion is drawn that corticosterone has significant additional diabetogenic effects upon biochemical functions of liver mitochondria in the SZ-induced diabetic state which could occur through the hormone cellular receptors.
ABSTRACT
El presente trabajo estudió el efecto del frío sobre el consumo del oxígeno (CO) y la actividad *-glicerofosfato deshidrogenasa (*-GPD) en mitocondria cardíaca de ratas hipotiroideas (hipo) tratadas con T3, T4 o T4 más Acido lopanoico (IOP). Se usaron ratas Wistar macho de 200g de peso hechas hipotiroideas con la administración de I. Los animales fueron inyectadoss s.c., en dosis divididas, por 10 días, con una de las siguientes sustancias: T3, 300 ng/100g peso/día; T4, 2 *g/100g peso/día o T4 más IOP, 5 mg/100g peso/día, por 72 hs. previas al experimento. Una mitad de cada grupo fue mantenida a 4§C y el resto a 22§C, por 24 hs., y logo decapitados. Se aislaron las mitocondrias de corazón por métodos de rutina. El CO se midió polarográficamente usando L-malato, L-glutamato y malonato como sustratos. La actividad mitocondrial *-GPD se medió por un método microcolorimétrico. Los resultados correspondientes a 16 o 20 ratas/grupo (4 o 5 "pooles" de 4 corazones cada uno) fueron los isguientes: En las ratas mantenidas a 22§C el CO (en ng at. de oxíg./min/mg prot.; Estado 3) de las Hipo+T4 fue de 69 ñ 10; en el grupo tratado con T4+IOP fue de 75 ñ 11 y ...
Subject(s)
Rats , Animals , Male , Cold Temperature , Oxygen Consumption/physiology , Glycerolphosphate Dehydrogenase/metabolism , Mitochondria, Heart/physiology , Adaptation, Physiological , Body Temperature Regulation , Thyroid Hormones/therapeutic use , Hypothyroidism/drug therapy , Hypothyroidism/physiopathology , Rats, Inbred Strains , Triiodothyronine/administration & dosageABSTRACT
Chronic diabetes induced by the injection of streptozotocin in male and female albino adult rats provoked significant alteration of liver mitochondrial function 30 or 35 days after administration of the drug. Thus, we obtained mean values of respiratory control (RC) and state 3 (S3) with 3-hydroxybutyrate as substrate 40 or 50% lower than those of non-diabetic animals. With other substrates (malate-glutamate, succinate) the decrease of RC and S3 in the diabetic animals was 20% or 30% of the normal mean values. The osmotic damped oscillations of mitochondria were measured as another parameter of the organella function. It was assayed with valinomycin as K+ ionophore and succinate as substrate. In diabetic rats of both sexes we found a significant increase of the mean damping factor of these oscillatory variations compared with normal values. The above-mentioned results indicate a lesser elasticity and an impaired K+ transport of mitochondria across the inner membrane in diabetic animals. Both reported parameters, respiration and oscillatory variations of liver mitochondria, were measured in normal non-diabetic rats and in the groups of diabetic rats referred to as follows: 1) intact (male and female), 2) gonadectomized (male and female), 3) oophorectomized with restitution of 17 beta-estradiol. Ovariectomized diabetic rats showed a significant increase in the values of the RC and S3 of liver mitochondria compared with intact female diabetic animals. The withdrawal of the ovarian hormone in female diabetic rats significantly decreased the values of the damping factors of the oscillatory mechanism and they were similar to the normal. The restitution of 17 beta-estradiol to oophorectomized diabetic rats resulted in a decrease of liver mitochondrial respiration. The damping factor of liver mitochondria of the oophorectomized diabetic rats treated with the estrogen showed values significantly higher than those of female diabetic animals without the hormone and similar to the values of the intact diabetic female rats. Castration of male rats did not produce any effect upon the liver mitochondrial RC and S3 or upon the mean damping factor of the oscillatory variation either. Then the castration of male diabetic rats did not modify the mitochondrial function. In contrast, the oophorectomy of diabetic animals produced amelioration of mitochondrial respiration and oscillatory behavior. The conclusion is drawn that in female rats the circulating 17 beta-estradiol produced a pernicious effect upon liver mitochondrial function in the experimental diabetic state.
Subject(s)
Diabetes Mellitus, Experimental/physiopathology , Estradiol/pharmacology , Mitochondria, Liver/drug effects , Orchiectomy , Ovariectomy , Oxygen Consumption/drug effects , Animals , Female , Hydroxybutyrate Dehydrogenase/metabolism , Male , Mitochondria, Liver/metabolism , Mitochondria, Liver/physiology , Rats , StreptozocinABSTRACT
Chronic diabetes induced by the injection of streptozotocin in male and female albino adult rats provoked significant alteration of liver mitochondrial function 30 or 35 days after administration of the drug. Thus, we obtained mean values of respiratory control (RC) and state 3 (S3) with 3-hydroxybutyrate as substrate 40 or 50
lower than those of non-diabetic animals. With other substrates (malate-glutamate, succinate) the decrease of RC and S3 in the diabetic animals was 20
or 30
of the normal mean values. The osmotic damped oscillations of mitochondria were measured as another parameter of the organella function. It was assayed with valinomycin as K+ ionophore and succinate as substrate. In diabetic rats of both sexes we found a significant increase of the mean damping factor of these oscillatory variations compared with normal values. The above-mentioned results indicate a lesser elasticity and an impaired K+ transport of mitochondria across the inner membrane in diabetic animals. Both reported parameters, respiration and oscillatory variations of liver mitochondria, were measured in normal non-diabetic rats and in the groups of diabetic rats referred to as follows: 1) intact (male and female), 2) gonadectomized (male and female), 3) oophorectomized with restitution of 17 beta-estradiol. Ovariectomized diabetic rats showed a significant increase in the values of the RC and S3 of liver mitochondria compared with intact female diabetic animals. The withdrawal of the ovarian hormone in female diabetic rats significantly decreased the values of the damping factors of the oscillatory mechanism and they were similar to the normal. The restitution of 17 beta-estradiol to oophorectomized diabetic rats resulted in a decrease of liver mitochondrial respiration. The damping factor of liver mitochondria of the oophorectomized diabetic rats treated with the estrogen showed values significantly higher than those of female diabetic animals without the hormone and similar to the values of the intact diabetic female rats. Castration of male rats did not produce any effect upon the liver mitochondrial RC and S3 or upon the mean damping factor of the oscillatory variation either. Then the castration of male diabetic rats did not modify the mitochondrial function. In contrast, the oophorectomy of diabetic animals produced amelioration of mitochondrial respiration and oscillatory behavior. The conclusion is drawn that in female rats the circulating 17 beta-estradiol produced a pernicious effect upon liver mitochondrial function in the experimental diabetic state.
ABSTRACT
In the present study it is shown that streptozotocin (SZ)-induced chronic diabetes of female albino rats produced significant alterations in liver mitochondrial function after 30-35 days of diabetes. The disturbances were as follows: (1) a significant fall of the mean values of the respiratory control ratio and of state 3 of respiration using three substrates, 3-hydroxybutyrate, malate-glutamate and succinate, and (2) a significant increase of the mean damping factor of the oscillatory osmotic variations (with valinomycin as K+ ionophore and succinate as substrate). The same mitochondrial function parameters were analyzed for comparison in control non-diabetic rats (group N) and in the following groups of female rats with chronic diabetes: intact (group I), oophorectomized (6 days after the injection of SZ) (group O), and oophorectomized with restitution therapy of 17 beta-estradiol (from the operation until the day before killing) (group O + Eol). The O group showed significantly higher values of the respiratory control ratio and of state 3 of respiration and significantly lower damping factors than group I. The restitution treatment in the O + Eol group restored the mitochondrial functions assayed to values similar to those of group I. These data provide strong evidence that estrogens exert a negative effect at the molecular level upon impaired liver mitochondrial functions in SZ-induced diabetes.
Subject(s)
Diabetes Mellitus, Experimental/metabolism , Estradiol/pharmacology , Mitochondria, Liver/metabolism , Ovariectomy , Animals , Female , Kinetics , Mitochondria, Liver/drug effects , Oxygen Consumption/drug effects , Rats , Reference ValuesABSTRACT
Liver D-3-hydroxybutyrate dehydrogenase (OHBD) is subjected to estrogen modulation. Estrogen action was demonstrated by (a) the lesser activity of liver OHBD in female rats, as compared with their male counterparts; (b) the increase of OHBD activity after ovariectomy of sexually mature rats; (c) the decrease of OHBD activity after treatment of gonadectomized or normal rats with 17 beta-estradiol or with artificial estrogens; (d) the decrease of OHBD activity in female rats during sexual development; (e) the effects of tamoxifen on the enzyme activity. The kinetics of OHBD reaction using liver mitochondria from estrogen-treated rats showed a 50% decrease of Vmax, as compared with the control value, in contrast to the other parameters which did not vary. These results, taken together with the effect of estrogens on liver mitochondrial phospholipids, point to a decreased content of OHBD in liver mitochondria from estrogen-treated rats. In contrast to OHBD, succinate dehydrogenase and cytochrome oxidase activities, mitochondrial protein synthesis and L-malate + L-glutamate oxidation by coupled liver mitochondria either increased or were not affected by estrogens. Kidney and heart OHBD were affected by ovariectomy and estrogens like the liver enzyme, though to a lesser degree.