Gene expression of vasopressin receptor type 2 and aquaporin 2 in acute renal failure versus chronic renal failure in rats

ABSTRACT

Urinary concentration decreases in response to a reduction of functioning renal mass. Although a variety of factors have been implicated, the pathogenesis of impaired urinary concentration ability in acute renal failure [ARF] and in chronic renal failure [CRF] especially the cellular and molecular defects, were poorly understood. Our study therefore aimed to present a possible explanation for the pathogenesis of impaired urinary concentration and the molecular defect in kidney tissue of experimental ARF and CRF rat models and aimed to find and compare any molecular defect difference between ARF and CRF. Thirty albino adult male rats were used in our study and the animals were divided into three groups. Group I Sham-operated controls [n=10]. Group II Renal ischemia-reperfusion injury group [n=10] in which the renal artery and vein were bilaterally exposed and occluded for 30min with vascular clamps to produce renal ischemia-induced acute renal failure [ARF], the clamps were removed to allow kidney reperfusion then the animal sacrified after 24H. Group III Chronic renal failure group [n=10], this group of animals underwent right total nephrectomy and removal of 2/3 of the left kidney and the experimental protocol lasted about one month then the animals were sacrified. Blood, urine and kidney tissue samples were collected from the three groups to measure serum urea and creatinine and 24 hour-urinary albumin for evaluation of kidney function and to measure aquaporin 2 water channel and vasopressin-receptor type 2 [V[2]] gene expressions in kidney tissue. Kidney function tests as regards serum urea, serum creatinine and 24 hour-urinary albumin in group II and group III showed a significant [p<0.05] increase in comparison to control group [group I]. Ischemic-reperfusion rats [group II] showed the highest of these parameters indicating that, they had the worst kidney function. A significant [p<0.05] decrease in vasopressin-receptor type 2 [V[2]] mRNA expression in kidney tissue was shown in group II [ARF] and group III in comparison to the control rats [group I] with the highest reduction in group II. A similar result was found as regards Aquaporin 2 water channel mRNA expression with a significant [p<0.05] reduction in group II and group III in comparison to group I, and the highest reduction was seen in group II among the three studied groups. In both ischemia-reperfusion rats and CRF rats, the ischemic and nephrectomy insults were associated with decreased mRNA expression of the aquaporin 2 and vasopressin-receptors type 2 [V[2]] in the kidney tissue, coinciding with the impairment of kidney function. This may contribute to the impairment in urinary concentration in the post-ischemic period and the urinary concentration defect associated with CRF