Renal prostaglandin E₂ synthesis and degradation in the developing rat

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 medullary 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 GFR may be age-related differences in renal cortical prostaglandin turnover.