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Hyperparathyroidism, secondary to renal disease, is thought to cause high bone turnover via prostaglandin E[sub 2] (PGE[sub 2] ). Diets high in n-3 fatty acids reduced PGE[sub 2] . Thus the objective was to compare the effect of diets high in n-6 and n-3 fatty acids on hyperparathyroidism, bone turnover, and PGE[sub 2] in Han:SPRD-cy rats that develop polycystic kidney disease (PKD). Weanling male rats (n=58) were randomized to diets made with either corn or flaxseed oil (5%) for 8 weeks, followed by measurement of plasma parathyroid hormone (PTH), osteocalcin, urinary N-telopeptide (NTX), and ex vivo release of PGE[sub 2 ] from femur. Plasma PTH was elevated (P<0.01) as a result of PKD. Mean values for plasma osteocalcin and urinary NTX were elevated (P<0.01) by PKD but not altered by diet. In contrast, values for PGE[sub 2] were lowest in the PKD rats fed flaxseed oil compared with PKD rats fed corn oil and compared with non-affected rats fed either oil. Rats with PKD have high-turnover bone disease, likely due to hyperparathyroidism, that is unaffected by feeding corn or flaxseed oils. Since PGE[sub 2 ] release is lower in the presence of high bone turnover, the high bone turnover in evolving rat uremia is not likely to be mediated by PGE[sub 2] . [ABSTRACT FROM AUTHOR]

Dietary protein restriction slows progression of the Han:SPRD-cy rat model of polycystic kidney disease. We undertook studies to examine the relative changes in interstitial and tubular pathology as a result of feeding an 8% casein (LP) diet to Han:SPRD-cy rats. Archival tissue from a previous study comparing LP and 20% casein (NP) diets was examined morphometrically after immunohistochemical or histochemical staining for apoptosis, proliferation antigens, interstitial fibrosis, and macrophage infiltration. Expression of common extracellular matrix genes was measured by Northern analysis. Animals fed LP diet demonstrated reduced tubular epithelial remodelling compared with animals fed NP diet by both proliferating cell nuclear antigen-positive cells (57.5 vs. 71.6 cells/mm epithelium, P=0.007) or apoptosis (31.2 vs. 35.6 cells/mm epithelium, P=0.006). Interstitial pathology demonstrated that LP feeding was associated with proportionately greater reductions in interstitial fibrosis (0.3 vs. 1.3 ml/kg body weight, P=0.003), interstitial cellularity (361 vs. 604 cells/high-power field, P=0.0002), and interstitial macrophages (67 vs. 149 cells/high-power field, P=0.0002). Northern analysis only revealed significantly lower levels of monocyte chemoattractant protein mRNA (P=0.04) in animals fed the LP diet. Dietary protein restriction modifies both tubule and interstitium, with significant impact upon interstitial inflammation and fibrosis in the Han:SPRD-cy rat. [ABSTRACT FROM AUTHOR]