Effect of feeding on glomerular filtration rate and proteinuria in conscious aging rats

Abstract

Food intake increases glomerular filtration and proteinuria in adult rats. That this postprandial hyperfiltration could be age dependent was investigated in 3-, 10-, 20-, and 30-mo-old rats. Glomerular filtration rate and protein excretion were measured in fed or 24 h fasted conscious animals. In the 3-mo-old rats food ingestion increased renal filtration by 45% from 1.17 +/- 0.08 to 1.73 +/- 0.11 ml.min-1.g kidney wt-1 (n = 6). As the animals became older, the differences between fed and fasted periods became smaller: in 30-mo-old rats glomerular filtration rate was 0.85 +/- 0.03 and 1.01 +/- 0.06 ml.min-1.g kidney wt-1 (n = 6) in fasted and fed conditions, respectively. Proteinuria, which was mainly albuminuria, increased slightly with age and was more markedly reduced by acute food restriction in the 30-mo-old than in the 3-mo-old rats. Because the renin-angiotensin system activity decreases with age, its role in postprandial hyperfiltration was assessed by measuring glomerular filtration in 3-mo-old animals whose angiotensin II converting-enzyme activity was chronically inhibited by daily administration of perindopril. In such experimental conditions there was no longer a difference in renal filtration between fed and fasted rats. These data indicate that 1) postprandial increase in glomerular filtration is to some extent related to the renin-angiotensin system activity; 2) short-term reduction of food intake reduces proteinuria even in senescent rats, although the feeding dependence of the glomerular filtration is blunted with age.

Prevention of cardiovascular and renal pathology of aging by the advanced glycation inhibitor aminoguanidine.

“…NO'-mediated renal responses are reportedly blunted in the aging rat (36). The maintenance of a normal NO'-dependent dilatory reserve in the systemic vasculature by AG may provide a basis to speculate significant opposing action to renal vasoconstrictive forces, resulting in a lowering of renal vascular resistance adequate enough to maintain normal renal blood flow.…”

Inhibition of Renal Dipeptidyl Peptidase IV Enhances Peptide YY1–36-Induced Potentiation of Angiotensin II-Mediated Renal Vasoconstriction in Spontaneously Hypertensive Rats

“…Food intake increases plasma levels of PYY 1-36 by as much as 10-fold after a large, fatty meal (Pappas et al, 1986;Armstrong et al, 1991;Fu-Cheng et al, 1997;Anini et al, 1999;MacIntosh et al, 1999;Teixeira et al, 2001;Korner et al, 2005). In addition, food intake and obesity are associated with activation of the renin-angiotensin system (Corman et al, 1988;Cassis et al, 1998;Ahmed et al, 2005). Therefore, frequent intake of large, fatty, calorie-laden meals associated with obese-prone eating patterns in type 2 diabetics would 1) increase time-averaged circulating levels of PYY 1-36 because the intestinal L-cells would be driven to release larger pulses of PYY 1-36 (because of larger meals) and more frequently pulses of PYY 1-36 (because of more frequent large meals) and 2) stimulate the renin-angiotensin system.…”

Multiple Factors Influence Glomerular Albumin Permeability in Rats

“…Micropuncture data have been generated using FMW rats in the fasting condition, whereas we used SMW rats in the fed condition. 18,19 Because feeding status increases urinary albumin and prostprandial GFR has previously been quantified in rats, 27 we first set out to determine the effects of feeding on GSC A . As shown in Figure 1, after an overnight fast SMW rats showed a marked reduction in GSC A : from 0.03560.005 to 0.01660.004 (mean 6 SD; P,0.01).…”