In glomeruli isolated from adult rats, arachidonic acid (C20:4) is metabolized through at least two different pathways: the lipoxygenase and the cyclooxygenase pathway, resulting in the synthesis of 12-hydroxyeicosatetraenoic acid (12-HETE) and four prostaglandins (PG) respectively. Because renal blood flow (RBF) and glomerular filtration rate (GFR) increase during development, and because C20:4 metabolites are implicated in their local regulation, the conversion of 3H-C20:4 was studied in 3 groups of rats; group A: 4 days old, 10 g; group B: 10 days old, 25 g; group C: 60 days old, 200 g. Glomeruli mechanically isolated from blanched kidneys were incubated with 5.4 X 10(-8) M 3H-C20:4. Lipoxygenase and cyclooxygenase products were extracted and resolved by high-performance liquid chromatography (HPLC); quantitative determination of PGs was performed by radioimmunoassay (RIA). The results are: (1) conversion of C20:4 to lipoxygenase product is predominant in comparison to cyclooxygenase products; (2) conversion of labeled C20:4 into 12-HETE is constant with age; (3) identified cyclooxygenase products, PGE2, and particularly PGF2 alpha are maximum in group B; (4) the variation of C20:4 metabolism during development suggest that these products may be involved in the maturation and the regulation of glomerular functions.