Angiotensinogen in cerebrospinal fluid corresponds chromatographically to the gamma-form of plasma angiotensinogen

Angiotensinogen (Aogen) (CA 11002-13-14), the prohormone of the neuro- and vasoactive peptide angiotensin II (Ang II) (CA 11128-99-7), is found in dog brain as well as in dog plasma. At 2-4 micrograms/ml CSF, Aogen comprises 1-2% of the total protein in dog CSF. Immunopurified CSF and plasma Aogen were compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and anion-exchange HPLC. Two major (alpha- and beta-) forms and one minor (gamma-) form of Aogen were observed in dog plasma. The majority of Aogen in dog CSF was chromatographically identical to the gamma-form of plasma Aogen; alpha- and beta-Aogen forms comprised less than 5% of the total CSF Aogen. The N-terminal amino acid sequences of alpha-, beta-, and gamma-Aogen identified these proteins as members of the Aogen family. The N-terminal amino acid sequence of CSF gamma-Aogen was Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-Leu-Leu-Val-Tyr-Ser-Lys-Ser-Ser-(X)-Glu- . More basic than either alpha- or beta-Aogen, gamma-Aogen was shown to be a glycoprotein with an apparent molecular weight (Mr) of 58,000. CSF [des Ang I]-Aogen exhibited a greater anion-exchange HPLC retention. CSF, however, contained only minor amounts of [des Ang I]-Aogen. These analyses have demonstrated that brain overwhelmingly releases one particular Aogen into the CSF; however, very little of this brain Aogen is utilized for the production of Ang I.