1. The distribution of angiotensinogen and endogenous renin-like activity were analysed in different areas of the central nervous system in normal and DOC-salt-treated hypertensive rats.
2. Angiotensinogen concentration and renin-like activity were significantly increased in the cerebral cortex, cerebellum, hypothalamus and brain stem of the DOC-salt-treated rats 30 days after the initiation of the experiment.
3. Influence of plasma contamination on the former results was evaluated by the determination of (a) plasma angiotensinogen concentration in control and treated animals and (b) blood content remaining in the different regions of the central nervous system, after saline perfusion of the brain, in a group of normal rats.
4. Plasma angiotensinogen concentration was significantly decreased in DOC-salt-treated rats, therefore blood contamination would tend to diminish the magnitude of increase in central nervous system angiotensinogen in these animals.
5. Present results have shown an increased concentration of angiotensinogen in some areas of the central nervous system in DOC-salt-treated rats. The results have also confirmed an enhanced activity of the endogenous renin-like enzyme in the same regions; this change seems to be mainly due to the increment in angiotensinogen. Increased formation of central angiotensin could be involved in the development of DOC-salt hypertension. The biosynthetic pathways of renin substrate as well as its endogenous regulation remain undetermined.