Increase In Glomerular Volume Research Articles

Glomerular filtration, renal blood flow, and solute excretion in conscious aging rats.

Measurement of daily food and water intakes and of renal water and solute excretion in 10-, 20-, and 30-mo-old female rats revealed that they ate the same amounts of food and excreted the same amounts of glucose, sodium, and potassium irrespective of age but that in the 30-mo-old rats phosphate, calcium, and magnesium excretion rose. The glomerular filtration rate and p-aminohippuric acid clearance measured in conscious animals following moderate volume expansion did not differ with age, when expressed per 100 g body wt, but decreased markedly in the 30-mo-old rats when compared with kidney weight. This was related to the senile hypertrophy of the kidneys in the 30-mo-old group, which was reflected by increases in glomerular volume and length of the proximal tubules and by enlargement of the medulla, with the number of nephrons remaining constant with age. There was no evidence of glomerulosclerosis or kidney disease, and proteinuria remained at a low level in all three age groups. These results suggest that the diminished renal filtration rate observed in both conscious and anesthetized senescent rats is due to a reduced supply of blood per gram of kidney tissue and not to loss of nephrons.

Morphologic correlates of renal growth arrest in neonatal partial ureteral obstruction.

To investigate the morphologic correlates of decreased renal blood flow and growth arrest resulting from chronic partial ureteral obstruction in the neonate, guinea pigs were subjected to unilateral ureteral constriction within the first 2 days of life and were studied at 3 and 8 wk of age. Severity of histologic changes in the obstructed and intact contralateral kidney was assessed by light microscopy. Morphometric glomerular measurements were made using a computerized tracing device. Since contralateral nephrectomy or administration of angiotensin converting enzyme inhibitor (enalapril) result in increased blood flow to the obstructed kidney, morphologic changes were also examined in separate groups of animals subjected to these maneuvers, and were compared to appropriate controls. Ipsilateral chronic partial ureteral obstruction resulted in decreased glomerular volume (p less than 0.0001) and increased glomerular crowding associated with tubular dilatation and progressive glomerular sclerosis, tubular atrophy, and interstitial fibrosis. The intact contralateral kidney underwent hypertrophy with increase in glomerular volume (p less than 0.0001) and decreased glomerular density. Contralateral nephrectomy prevented the decrease in glomerular volume in the obstructed kidney and resulted in decreased glomerular density and reduced tubular atrophy at 3 wk of age. Enalapril prevented the decrease in glomerular volume at 3 wk of age, but glomerular and tubular changes progressed and were unaffected by enalapril at 8 wk. Left kidney glomerular volume was directly related to renal blood flow (r = 0.71, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral complications of serum sickness.

Salt restriction inhibits renal growth and stabilizes injury in rats with established renal disease. Male Munich-Wistar rats that underwent right nephrectomy and segmental infarction of two thirds of the left kidney were fed standard chow for 4 wk and then randomly assigned to ingest standard or low-salt chow for an additional 4 wk. Four wk after ablation, rats had systemic hypertension, proteinuria, and glomerular sclerosis. The prevalence of sclerosis, protein excretion rate, and glomerular volume increased between the fourth and eighth week in rats that were fed standard chow, however, in rats that were fed low-salt chow, the increase in glomerular volume and development of further glomerular sclerosis was prevented whereas the protein excretion rate actually declined. Micropuncture studies performed 8 wk after ablation revealed that the glomerular hydraulic pressure was elevated in remnant kidneys and was not affected by salt restriction. This study demonstrates that dietary salt restriction can prevent further glomerular injury and reduce proteinuria even when instituted in rats with established renal disease. These findings are also consistent with the hypothesis that glomerular hypertrophy promotes injury in this model of hypertension and progressive renal disease.