Prostaglandin E2 binding sites in human renal tissue: characterization and localization by radioligand binding and...

The prostaglandin E2 (PGE2) binding site in human kidney was characterized in membrane preparations from cortex, outer medulla and inner medulla using radioligand binding techniques. The localization of the binding sites for [3H]PGE2 was visualized autoradiographically. In the membrane suspensions, the highest level of specific [3H]PGE2 binding was detected in the outer medulla (Bmax = 335 +/- 28 fmol mg-1 protein) followed by the inner medulla (Bmax = 258 +/- 21 fmol mg-1 protein) and the cortex (Bmax = 143 +/- 22 fmol mg-1 protein). The binding was of high affinity with KD values between 3.7 and 6.2 nM in the various regions. Unlabelled prostaglandins competed for the [3H]PGE2 binding sites in the following rank order of potency: PGE2 approximately PGE1 greater than PGF2 alpha approximately PGA2 greater than PGB2 greater than PGI2 approximately PGD2. Autoradiographs revealed that a high density of [3H]PGE2 (2 nM) binding sites were located on the distal tubule, particularly on the thick ascending limbs of Henle. Lower densities of [3H]PGE2 binding sites were found on the medullary collecting ducts and possibly on the thin loops of Henle. In contrast, no specific [3H]PGE2 binding could be found on the proximal tubule, glomeruli or on blood vessels. This distribution is in accordance with the assumed site of action for the salt and water regulatory function of PGE2.