Renal haemodynamics and function in weanling rats treated with enalapril from birth

The Impact of Functional and Structural Maturation of the Kidney on Susceptibility to Drug and Chemical Toxicity in Neonatal Rodents

Drug responses are often unpredictable in juvenile animal toxicity studies; hence, optimizing dosages is challenging. Renal functional differences based on age of development will often result in vastly different toxicologic responses. Developmental changes in renal function can alter plasma clearance of compounds with extensive renal elimination. Absorption, distribution, metabolism, and excretion of drugs vary depending on animal age and kidney maturation. Toxicity can result in malformations or renal degeneration. Although renal morphologic development in humans generally occurs in utero, maximal levels of tubular secretion, acid-base equilibrium, concentrating ability, or glomerular filtration rate (GFR) are reached postnatally in humans and animals and subject to drug effects. Maturation of renal metabolism and transporters occurs postnatally and plays a critical role in detoxification and excretion. Maturation times must be considered when designing juvenile toxicity studies and may require cohorts of animals of specific ages to achieve optimal dosing schemes and toxicokinetics. In recent years, critical end points and windows of susceptibility have been established comparatively between species to better model pharmacokinetics and understand pediatric nephrotoxicity. There are examples of agents where toxicity is enhanced in neonates, others where it is diminished, and others where rat nephrotoxicity is expressed as juvenile toxicity, but in humans as gestational toxicity.

Effect of enalapril in cisplatin-induced nephrotoxicity in rats; gender-related difference

Background:

The function of renin angiotensin system (RAS) is gender-related, and this system affects cisplatin (CP)-induced nephrotoxicity. In this study, we compared the effect of enalapril as an angiotensin-converting enzyme (ACE) inhibitor on CP-induced nephrotoxicity between male and female rats.

Materials and Methods:

Sixty-two adult male and female Wistar rats were divided into eight groups. Both genders received CP (2.5 mg/kg, i.p.) and enalapril (30 mg/kg, i.p.) for 7 days in compared with CP alone or enalapril alone or vehicle alone treated groups. At the end of the experiment, blood samples were obtained, and the kidney tissue was investigated for histopathological changes.

Results:

CP increased the serum levels of blood urea nitrogen and creatinine as well as kidney weight and kidney tissue damage score in both genders (P < 0.05). However, not only enalapril failed to ameliorate the aforementioned parameters in both genders, but also it intensified nephrotoxicity in females (P < 0.05). In addition, enalapril enhanced body weight loss induced by CP in females (P < 0.05). CP alone decreased kidney level of nitrite in both genders (P < 0.05) and enalapril could not reverse this decreasing. The combination of enalapril and CP significantly increased serum level of nitrite in females, but this was not observed in males (P < 0.05).

Conclusion:

Enalapril as an ACE inhibitor failed to ameliorate nephrotoxicity induced by CP in both male and female rats. In addition, enalapril aggravated CP-induced nephrotoxicity in female possibly due to gender-dependent RAS response.

The role of oxidative stress in renal injury induced in rats by losartan exposure during lactation

INTRODUCTION

Rats exposed to angiotensin II (AII) receptor antagonists during lactation present progressive disturbances in renal development that lead to progressive alterations in renal function and structure. This study evaluates the role of oxidative stress in the renal changes induced by exposure to losartan, a type 1 AII receptor antagonist, in rats during lactation.

MATERIALS AND METHODS

Male Wistar pups were divided into: Control, pups of dams that received 2% sucrose solution; Control-tempol, pups of dams that received tempol (0.34 g/l), a superoxide dismutase mimetic compound; Losartan, pups of dams that received losartan (100 mg/kg/day), and Losartan-tempol, pups of dams that received losartan and tempol. Losartan and/or tempol were administered during lactation. Blood and urine samples were collected at 21 or 60 days, and the kidneys were removed.

RESULTS

Losartan-treated pups exhibited disturbances in renal function and structure that persisted into adulthood. Tempol treatment reduced oxidative stress and attenuated the changes induced by losartan in the glomerular filtration rate, desmin expression at the glomerular edge, vimentin in tubular cells, as well as apoptosis and inflammatory infiltration in the renal cortex.

CONCLUSION

Oxidative stress contributes at least in part to the renal injury observed in pups exposed to losartan during lactation.

Intrauterine growth restriction: fetal programming of hypertension and kidney disease

The etiology of hypertension historically includes 2 components: genetics and lifestyle. However, recent epidemiologic studies report an inverse relationship between birth weight and hypertension suggesting that a suboptimal fetal environment may also contribute to increased disease in later life. Experimental studies support this observation and indicate that cardiovascular/kidney disease originates in response to fetal adaptations to adverse conditions during prenatal life.

Changes in renal hemodynamics and excretory function induced by a reduction of ANG II effects during renal development

The aim was to evaluate whether blockade of ANG II effects during renal development modifies the renal response to an increment of plasma amino acid concentration. It was also examined in anesthetized rats whether the reduction of the renal ability to eliminate an acute volume expansion (VE), elicited by blockade of ANG II during renal development, is sex and/or age dependent. Newborn Sprague-Dawley rats were treated with vehicle or an AT(1)-receptor antagonist (ARA) during postnatal nephrogenesis. Amino acid infusion induced increments (P < 0.05) of glomerular filtration rate (31 +/- 6%) and renal plasma flow (26 +/- 5%) in male but not in female vehicle-treated rats. Natriuretic and diuretic responses to amino acid infusion were similar in male and female vehicle-treated rats. These renal hemodynamics and excretory responses to amino acid infusion were abolished in ARA-treated rats. Renal responses to VE were evaluated at 3-4 and 9-10 mo of age in vehicle and ARA-treated rats. VE-induced natriuresis and diuresis were reduced by more than 38% (P < 0.05) in 3- to 4-mo-old male and female ARA-treated rats. An age-dependent reduction (P < 0.05) in the renal ability to eliminate VE was found in male but not in female rats treated with ARA. Our results demonstrate that the renal effects induced by an increment in amino acids are abolished when ANG II effects have been reduced during nephrogenesis. In addition, this reduction of ANG II effects elicits an impairment of the renal ability to eliminate an acute VE in males and females, which is aggravated by age only in male rats.

Sex and age differences of renal function in rats with reduced ANG II activity during the nephrogenic period

This study was designed to test the hypothesis that blockade of angiotensin II effects during renal development accelerates the aging-related changes in renal hemodynamics and proteinuria, and that these changes are sex dependent. It has also been examined whether the deterioration of urinary concentrating ability elicited by angiotensin II blockade is sex and/or aging dependent. Newborn Sprague-Dawley rats were treated with vehicle or an AT(1) angiotensin II receptor antagonist (ARA) during the first 14 postnatal days. Blood pressure, glomerular filtration rate, proteinuria, and urinary concentrating ability in response to dehydration were examined in conscious rats at 3 and 11 mo of age. ARA treatment elicited a similar increment in blood pressure in males and females that was greater (P < 0.05) at 11 than at 3 mo of age. Glomerular filtration rate only decreased (P < 0.05) in 11-mo-old male ARA-treated rats (0.59 +/- 0.07 vs. 0.80 +/- 0.07 ml.min(-1).g(-1) in control group). At 3 mo of age, proteinuria increased in male (107%) but not in female ARA-treated rats. However, at 11 mo of age, proteinuria increased in both sexes, but the increment was greater (P < 0.05) in male (244%) than in female (138%) ARA-treated rats. Renal ability to concentrate urine in response to prolonged water dehydration was only reduced in ARA-treated males. The reduction of urinary concentrating ability was accentuated by aging. Therefore, we conclude that blockade of angiotensin II effects during renal development elicits an important deterioration of cortical and medullary function that is sex and aging dependent.

The renin-angiotensin system in the development of the congenital anomalies of the kidney and urinary tract

PURPOSE OF REVIEW

Recognition of the dramatically expanded functional repertoire of the renin-angiotensin system now includes a role in morphogenesis of the kidney and urinary tract. On the basis of published data, the article presents formulations of mechanisms through which the system operates.

RECENT FINDINGS

Studies in humans and animals carrying defective angiotensin-related genes have provided unequivocal evidence that the renin-angiotensin system is involved in the normal development of both the kidney and the urinary tract. Angiotensin exerts its function through at least two different types of receptors, AT1 and AT2. AT1 mediates establishment of the ureteral peristaltic machinery, while AT2 mediates the early kidney and urinary tract morphogenesis. Disruption in receptor functions promotes development of congenital anomalies of the kidney and urinary tract.

SUMMARY

Angiotensin is involved in multiple steps of normal development of the kidney and urinary tract through two types of receptors. This takes place in concert with other functionally overlapping genes.