Influence of Nifedipine on Stone Formation and Renal Function in Cholesterol-Induced Nephrolithiasis in Rats

Abstract

Previous investigations showed that nifedipine limited calcium phosphate stone formation induced by a high-cholesterol diet in rats. This study was performed to obtain further insights into the effects of nifedipine on stone prevention, renal function and urine composition. Male Wistar rats were assigned to one of the following groups: (1) cholesterol diet (n = 22), (2) cholesterol diet plus nifedipine (n = 22) and (3) control (n = 6). A high-cholesterol diet was given for 4 weeks, nifedipine was administered by gavage to group 2 for 4 weeks (50 mg/kg/24 h). During weeks 1 and 4, 5 rats of each group were housed in metabolic cages for urine collection. Sodium (Na), calcium (Ca), magnesium (Mg), phosphate (P_i), citrate and creatinine were determined in the urine. The kidneys of 4 animals of group 1 and 2 were perfused and removed for histology after 1,2,3 and 4 weeks, respectively. Clearance studies (inulin, Na, Ca, Mg, P_i) were performed (n = 6/group) after 4 weeks. The cholesterol diet induced a marked renal stone formation which was significantly limited by nifedipine [calcification index (week 4) 1.75 ± 0.5 vs. 0.75 ± 0.5]. The sequential histological examinations showed that concrement formation started intracellularly after only 1 week in group 1 whereas in group 2 the first concretions were observed only after 3 weeks. The cholesterol diet induced an increased excretion of Ca and P_i, citrate and Mg were reduced. The concomitant application of nifedipine resulted in a higher excretion of Ca, Mg and citrate when compared to the cholesterol group. The inulin clearance was decreased in the latter group. Nifedipine limited this decrease. The fractional excretion (FE) of Ca, P_i and Mg was increased with the cholesterol diet. Nifedipine further increased the FE of Ca and Mg; FE of P_i was decreased when compared to group 1. Our results show that nifedipine limits nephrolithiasis and the deterioration of renal function in rats fed a cholesterol diet. Tubular cells obviously play a key role in the process of cholesterol-induced stone formation, probably being more important than changes in urine composition.

Clinical characteristics in urolithiasis formation according to body mass index

“…In Japan, detailed cross-sectional studies on the presence or absence of insulin resistance were performed, and they determined that female patients with kidney stones had high insulin resistance and insulin values, supporting the link between obesity and urolithiasis (21). Furthermore, one study reports that urolithiasis formation (calcium phosphate) is observed in the kidney when rats receive a high cholesterol diet (22).…”

Arterial Blood Pressure following Different Types of Urinary Stone Therapy

“…Alterations in calcium metabolism at the cellular level have been described in patients with arterial hypertension [14]. In experimental studies, similar mechanisms could be shown to play a role in the pathogenesis of stone formation [15, 16]. Since urolithiasis is a common disease (prevalence in industrialized nations 4%), the new onset of hypertension in those patients has a strong socioeconomic impact.…”