Localization of brain angiotensinogen mRNA by hybridization histochemistry.

The topographical distribution of rat brain angiotensinogen (Ao) mRNA was determined using hybridization histochemistry (in situ hybridization) with two different hybridization probes, a 32P-labelled 42 residue oligonucleotide and a full-length complementary (antisense) RNA labelled with either sulfur 35 or phosphorus 32. Low levels of Ao mRNA sequences were detected throughout the brain while high levels were restricted to specific areas often corresponding to classical nuclear boundaries. All areas in which angiotensin II-like immunoreactivity had been previously detected contained moderate to high levels of Ao mRNA and many previously undetected areas were also found to contain high levels of this mRNA. The results underline the ubiquitous presence of angiotensinogen-synthesizing cells in the brain and support previous evidence that the angiotensinogen gene could be expressed by several types of brain cells.