Elevated bone turnover in rat polycystic kidney disease is not due to prostaglandin E₂

Abstract.

Hyperparathyroidism, secondary to renal disease, is thought to cause high bone turnover via prostaglandin E₂ (PGE₂). Diets high in n-3 fatty acids reduced PGE₂. Thus the objective was to compare the effect of diets high in n-6 and n-3 fatty acids on hyperparathyroidism, bone turnover, and PGE₂ 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 PGE₂ 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 PGE₂ 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 PGE₂ 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 PGE₂.