Background: Prostaglandin (PG)-specific organic anion transporter (OAT-PG) is a recently identified renal transporter involved in the local clearance of prostaglandin E2 (PGE2). Since the renal biosynthesis of PGE2 is not increased during pregnancy, this transporter expression would affect the gestational changes in the renal PGE2 content. Methods: Kidneys from rats at different gestational stages were used to examine gestational changes in the renocortical PGE2 concentration. The renal expression of OAT-PG and the enzymes for PGE2 synthesis was also examined sequentially, together with the gestational changes in renal renin production. Results: The renocortical PGE2 concentration was significantly increased during midterm to late pregnancy, with a maximum increase of 47.6 ± 11.5% from the virgin value. Although the expression of the enzymes, such as cyclooxygenases and PG synthases, was not increased, that of OAT-PG was significantly decreased throughout pregnancy, inversely correlating with changes in the renocortical PGE2 concentration. Renal renin production was significantly increased during pregnancy. Conclusion: This study demonstrated for the first time that the tissue PGE2 concentration was increased in pregnant rat kidneys, which may be associated with the gestational rise in glomerular filtration rate. The decreased expression of OAT-PG was thought to be responsible for the increased tissue PGE2 content.
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