Favourable, significant effect of the dose-dependent treatment with RU 38486 (RU) on the alterations of the hepatic mitochondrial function of diabetic rats.

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.

Improving effects obtained by the ovariectomy or treatment with tamoxifen of female diabetic rats over the function and enzyme activities of liver mitochondria.

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.

Effects of withdrawal of glucocorticoids on improving the function and enzymatic activities of liver mitochondria in female diabetic rats.

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.

[Effects of cold on myocardial mitochondria respiration of rats with hypothyroidism treated with triiodothyronine]. / Efectos del frío sobre la respiración mitocondrial del miocardio de ratas hipotiroideas tratadas con triiodotironina.

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)

Efectos del frío sobre la respiración mitocondrial del miocardio de ratas hipotiroideas tratadas con triiodotironina. / [Effects of cold on myocardial mitochondria respiration of rats with hypothyroidism treated with triiodothyronine]

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)

Effects of withdrawal of glucocorticoids on improving the function and enzymatic activities of liver mitochondria in female diabetic rats.

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.

Effects of withdrawal of glucocorticoids on improving the function and enzymatic activities of liver mitochondria in female diabetic rats.

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.

Effect of ovarian hormones upon liver mitochondrial function in diabetic rats.

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.