Preconditioning with triiodothyronine improves the clinical signs and acute tubular necrosis induced by ischemia/reperfusion in rats

Background

Renal ischemia/reperfusion (I/R) injury is manifested by acute renal failure (ARF) and acute tubular necrosis (ATN). The aim of this study was to evaluate the effectiveness of preconditioning with 3, 3, 5 triiodothyronine (T₃) to prevent I/R renal injury.

Methodology/Principal Findings

The rats were divided into four groups: sham-operated, placebo-treated (SO-P), sham-operated T_3- treated (SO- T₃), I/R-injured placebo-treated (IR-P), and I/R-injured T₃-treated (IR- T₃) groups. At 24 h before ischemia, the animals received a single dose of T₃ (100 μg/kg). Renal function and plasma, urinary, and tissue variables were studied at 4, 24, and 48 h of reperfusion, including biochemical, oxidative stress, and inflammation variables, PARP-1 immunohistochemical expression, and ATN morphology. In comparison to the SO groups, the IR-P groups had higher plasma urea and creatinine levels and greater proteinuria (at all reperfusion times) and also showed: increased oxidative stress-related plasma, urinary, and tissue variables; higher plasma levels of IL6 (proinflammatory cytokine); increased glomerular and tubular nuclear PARP-1 expression; and a greater degree of ATN. The IR-T₃ group showed a marked reduction in all of these variables, especially at 48 h of reperfusion. No significant differences were observed between SO-P and SO-T₃ groups.

Conclusions

This study demonstrates that preconditioning rats with a single dose of T₃ improves the clinical signs and ATN of renal I/R injury. These beneficial effects are accompanied by reductions in oxidative stress, inflammation, and renal PARP-1 expression, indicating that this sequence of factors plays an important role in the ATN induced by I/R injury.

Long-term consequences of uninephrectomy in male and female rats

We investigated the effects of uninephrectomy (UNX) in 6-week-old male and female rats on blood pressure (BP), renal sodium handling, salt sensitivity, oxidative stress, and renal injury over 18 months postsurgery, studying control sham-operated and UNX-operated rats at 6, 12, and 18 months postsurgery, evaluating their renal sodium handling, BP, urinary isoprostanes, N-acetyl-β-D-glucosaminidase, and proteinuria before and after a 2-week high-salt intake period. At 18 months, plasma variables were measured and kidney samples were taken for the analysis of renal morphology and tissue variables. BP was increased at 6 months in male UNX rats versus controls and at 12 and 18 months in both male and female UNX rats and was increased in male versus female UNX groups at 18 months. UNX did not affect water and sodium excretion under basal conditions and after the different test in male and female rats at different ages. However, the renal function curve was shifted to the right in both male and female UNX rats. High-salt intake increased BP in both UNX groups at 6, 12, and 18 months and in the female control group at 18 months, and it increased proteinuria, N-acetyl-β-D-glucosaminidase, and isoprostanes in both UNX groups throughout the study. Renal lesions at 18 months were more severe in male versus female UNX rats. In summary, long-term UNX increased the BP, creatinine, proteinuria, pathological signs of renal injury, and salt sensitivity. Earlier BP elevation was observed and morphological lesions were more severe in male than in female UNX rats.

Cardiovascular and renal manifestations of glutathione depletion induced by buthionine sulfoximine

Oxidative stress contributes to the development of several cardiovascular diseases, including diabetes, renal insufficiency, and arterial hypertension. Animal studies have evidenced the association between higher blood pressure (BP) and increased oxidative stress, and treatment with antioxidants has been shown to reduce BP, while BP reduction due to antihypertensive drugs is associated with reduced oxidative stress. In 2000, it was first reported that oxidative stress and arterial hypertension were produced in normal Sprague-Dawley rats by oral administration of buthionine sulfoximine (BSO), which induces glutathione (GSH) depletion, indicating that oxidative stress may induce hypertension. The contribution of several potential pathogenic factors has been evaluated in the BSO rat model, the prototype of oxidative stress-induced hypertension, including vascular reactivity, endothelium-derived factors, renin-angiotensin system activity, TXA(2)-PGH(2) production, sodium sensitivity, renal dopamine-induced natriuresis, and sympathetic tone. This review summarizes the main factors implicated in the pathogenesis of BSO-induced hypertension and the alterations associated with GSH depletion that are related to renal function or BP control.

[Effects of thermo-oxidised oils on lipid peroxidation in experimental animals]

INTRODUCTION

The quality of fats and oils used for frying is as important as the quality of the final product since during the frying process oxidization by-products are formed and become part of the diet, being potentially harmful for the consumers' health.

OBJECTIVE

To determine the effects of thermo-oxidised fats and oils on the oxidization of plasma lipoproteins inexperimental rats.

METHODS

Determination by means of spectrophotometric techniques of those substances reacting with thiobarbituric acid and total cholesterol (enzymatic method) in the sera of 40 Wistar rats that consumed crude thermooxidised oils and fats with different levels of malonil aldehyde(MDA) for 30 days.

RESULTS

The group of rats receiving a diet with thermooxidised oils and fats experienced significant increases in MDA plasma levels throughout the study period, lipid peroxidation being higher with increasing MDA content (p < 0.05) regardless the type of fat compound consumed. However, those rats receiving crude oils and fats kept plasma levels of lipidic peroxides without significant changes throughout the experimental period (p > 0.05). By contrast, cholesterol levels increased towards the end of the experimental period in both the rats consuming crude fats and those consuming thermo-oxidised fats (p < 0.05).

CONCLUSIONS

Consumption of oils and fats submitted to repeat thermal heating has an influence on plasma lipidic peroxidation, which becomes higher with increasing number of heating processes applied, so that it would advisable not to abuse of reheating the oils used for frying foods.