Postnatal development of glomerular filtration rate (GFR) and renal blood flow is associated with a fall in renal vascular resistance that may be mediated by vasoactive substances. We examined differences in the regulation of one such substance, prostaglandin E2 (PGE2). The present studies examined renal cortical and medullary PGE2 synthesis and degradation in rats aged 20 days (30.7 g), 31 days (101 g), and 120 days (413 g). PGE2 synthesis in cortical microsomes was highest in 20-day-old rats compared to 31- and 120-day-old rats. In contrast, medullary PGE2 synthesis was lowest in 20-day-old rats compared to 31- and 120-day-old rats. Both cortical and medullary PGE2 degradation were highest in 20-day-old rats and decreased with age. Despite demonstrating significant age-dependent differences in cortical and medullary PGE2 synthesis, 11 days of aspirin given between age 20-31 days blocked PGE2 synthesis in cortex and medulla by 60 and 76%, respectively, but GFR was similar to control 31-day-old rats (0.78 +/- 0.04 ml/min/g kidney weight, aspirin-treated, versus 0.85 +/- 0.03 ml/min/g kidney weight, control), suggesting that observed age-dependent differences in renal PGE2 synthesis is not a major determinant of development of GFR. A more important determinant of GFR may be age- related differences in renal cortical prostaglandin turnover.