Two isoforms of the rat kidney EP₃ receptor derived by alternative RNA splicing: Intrarenal expression co-localization

Two different clones, named rEP_3A (∼2.2 kb) and rEP_3B (∼5.2 kb), were isolated from a rat kidney cDNA library by a homology screening approach. rEP_3A was shown to encode the rat kidney prostaglandin E receptor EP₃ subtype (rEP_3A receptor) (Takeuchi, K. et al. B.B.R.C. (1993) 194: 885). rEP3B receptor differs only in its carboxyl-terminal tail (Ile-336 to Pro-364) from rEP3A receptor. Southern blot analysis of genomic DNA has suggested that the EP₃ receptor gene is a single copy gene. RT-PCR using microdissected nephron segments showed co-expression of both receptor mRNAs specifically in distal nephron segments such as mTAL, cTAL, CCD and IMCD, whereas no significant expression of both receptor mRNAs was detected from GL, PCT, and PST. In conclusion, we have cloned an isoform of the rat kidney EP₃ receptor, rEP_3B receptor. rEP_3A and rEP_3B receptors are suggested to be derived by alternative RNA splicing, and both receptors are co-localized to distal tubules exerting an effect on water and electrolyte metabolism.