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

Two different clones, named rEP3A (approximately 2.2 kb) and rEP3B (approximately 5.2 kb), were isolated from a rat kidney cDNA library by a homology screening approach. rEP3A was shown to encode the rat kidney prostaglandin E receptor EP3 subtype (rEP3A 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, rEP3B receptor. rEP3A and rEP3B 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.