Ontogeny of angiotensin II type 2 (AT2) receptor mRNA in the rat

To study the distribution of the recently cloned angiotensin II type 2 (AT2) receptor in the rat fetus, a double stranded cDNA was generated by a new and recently described methodology requiring no cloning procedure. The cDNA obtained after reverse transcription (RT) and polymerase chain reaction (PCR) amplification corresponded to 500 base pairs of the gene coding sequence, and included the SP6 and T7 promoters at the 5' and 3' end, respectively. 35S-labeled cRNA sense and antisense probes were synthesized by in vitro transcription and used for in situ hybridization. From 13 to 19 days of gestation the AT2 receptor mRNA expression evolved and extended from a series of paired spots located para-axially, which were not identifiable at this level of observation, to a distribution in various mesenchymes (perichondrium, subepidermal layers), muscle cells (tongue, diaphragm, stomach), and classical target organs for Ang II (adrenal gland, kidney, aorta). During the first days after birth, the AT2 receptor mRNA decreased and remained detectable only in the adrenal gland and kidney. The distribution of the AT2 receptor mRNA appeared strikingly different from that of the AT1A receptor, which was studied in parallel for comparison.