Compartmental Study of Rat Renal Prostaglandin Synthesis during Development

Abstract

The biosynthesis of prostaglandins (PGs) from the endogenous and exogenous precursor, arachidonic acid (AA), in renal papilla, medulla and cortex from neonatal to adult rats was investigated. Rat renal papilla and medulla incubated in the presence of [1-¹⁴C]AA released radioactive PGE₂, PGF_2α and PGD₂ which increased with age. No radioactive prostaglandins were found in the supernatants of renal cortex at any age studied. The amount of total prostaglandins released from the endogenous precursor also increased from 10 to 70 days of age, PGD₂ being the prostaglandin that showed the most important rise. In the cortex, only PGE₂ release increased with age. Cyclooxygenase (COX) activity was measured in papillary, medullary and cortical homogenates by using [1-¹⁴C]AA as substrate. Papillary and medullary COX activity increased after 10 days of age and continued to rise up to day 30 thereafter remaining unaltered until adulthood. Cortical COX activity was very low and decreased with age. These findings indicate the low capacity of the neonatal rat kidney to synthesize PGs.

Coordinate regulation between the nuclear receptor peroxisome proliferator-activated receptor-γ and cyclooxygenase-2 in renal epithelial cells

“…1C). This profile is similar to the prostaglandin profile of the renal medulla [23]. PGs synthesis varied following the kinetic of COX-2 protein expression.…”

Changes in the Kinetic Properties of Renal Arachidonoyl-CoA Synthetase during Development in the Rat

“…The aim of the present report was to find an enzymatic basis that could explain the changes in arachidonate homeostasis and metabolism that occur during kidney maturation [2,4,13]. We had previously demonstrated that in newborn rats renal membrane phospholipids are almost depleted of arachidonic acid [4], show high avidity for exogenous arachidonic acid [2], and low prostaglandin synthesis [13]; while kidney maturation seemed to be characterized by enrichment in membrane arachidonic acid [4] and increase in prostaglandin synthesis [13].…”

“…As we have previously shown, in the neonatal kidney arachidonate content is low, fatty acid availability is scarce and cyclooxygenase activity is also low [4,13]. Thus, a highaffinity acyl-CoA synthetase is necessary to accomplish the storage of arachidonate in membrane phospholipids in the presence of a demand for prostaglandin synthesis.…”

“…We had previously demonstrated that in newborn rats renal membrane phospholipids are almost depleted of arachidonic acid [4], show high avidity for exogenous arachidonic acid [2], and low prostaglandin synthesis [13]; while kidney maturation seemed to be characterized by enrichment in membrane arachidonic acid [4] and increase in prostaglandin synthesis [13].…”

Cyclooxygenases in the Collecting Duct of Neonatal Rabbit Kidney

“…For the neonatal kidney little is known about the synthesis of the different prostaglandins and the expression of their specific receptors. A recent paper describes a low COX activity and consequently a low release of prostaglandin E 2 (PGE 2 ) in the cortex of the newborn rat, whereas the medulla was a rich source of PGE 2 , PGF 2á and PGD 2 [22]. However, the expression of specific PGE 2 receptors was shown in the neonatal rat cortex [23].…”