Sites of prostaglandin E2 (PGE2) synthesis along the rabbit nephron

The purpose of this study was to establish whether the nephron segments recognized as PGE2 target sites in the rabbit, i.e. the proximal tubule, the thick ascending limb and the collecting tubule, are also sites of PGE2 production. We therefore developed a microimmunoassay sensitive enough to allow the measurement of PGE2 on microdissected tubular segments about 1 mm in length. Under the conditions used (30 min incubation at 20 degrees C), a basal rate of PGE2 production was measured in the cortical (CCT) and medullary portions of the collecting tubule, as could be expected. In the presence of 10(-4) M sodium arachidonate, it was shown that: (1) The thin descending limb (TDL) is also an active site of PGE2 formation. When expressed per mm tubule length the amounts formed were lower in TDL than in CCT (14.1 +/- 2.7 SE pg/mm, n = 5, vs. 93.5 +/- 10.7, n = 8). They were quite comparable, however, when expressed per microgram total proteins (0.70 ng in TDL vs 0.6 in CCT). (2) A slight PGE2 production was noted in the connecting tubule but it was likely due to contamination by adjacent CCT cells. (3) In the other nephron segments, only negligible amounts of PGE2 were formed, which are probably of no physiological significance.