angiotensinogen and Neuroblastoma

Angiotensin II (Ang II) increases the level of tyrosine phosphorylation of several proteins in nondifferentiated NG108-15 cells, a hybrid derived from the fusion of mouse neuroblastoma and rat glioma cells. Conversely, incubation of NG108-15 cells with an angiotensin-converting enzyme (ACE) inhibitor decreased the basal level of tyrosine phosphorylation of proteins, suggesting that locally secreted Ang II may act as an autocrine regulator. By RT-PCR, we found that nondifferentiated NG108-15 cells contained the mRNA transcript of the rat angiotensinogen, mouse renin and rat ACE genes, thus confirming that NG108-15 cells contain all the elements of a local renin-angiotensin system.

Topics: Angiotensin II; Angiotensin-Converting Enzyme Inhibitors; Angiotensinogen; Animals; Cell Line; DNA Primers; Glioma; Hybrid Cells; Lisinopril; Mice; Neuroblastoma; Peptidyl-Dipeptidase A; Phosphorylation; Polymerase Chain Reaction; Rats; Renin-Angiotensin System; RNA, Messenger

Angiotensinogen in plasma is of hepatic origin, but many organs possess the ability to synthesize this protein because messenger RNA for angiotensinogen is widely distributed in the body. The cell types responsible for the extrahepatic synthesis of angiotensinogen remain to be identified. To examine whether renin-containing cells synthesize angiotensinogen, we have utilized a polyclonal antibody to angiotensinogen and immunoprecipitated metabolically labeled cells of two neuroblastomas known to contain renin. The results indicate that the cell line Neuro 2a synthesizes and releases a protein with a molecular mass of 57 kDa that is specifically recognized by the angiotensinogen antibody, indicating that Neuro 2a synthesizes angiotensinogen. Similarly, the cell line NB41A3 was also found to synthesize a protein specifically recognized by the antibody to angiotensinogen.

Topics: Angiotensinogen; Animals; Antibodies; Antigen-Antibody Complex; Cell Line; Electrophoresis, Polyacrylamide Gel; Molecular Weight; Neuroblastoma; Renin

Cultured neuroblastoma cells and neuroblastoma-glioma cells have been shown to contain renin activity, angiotensin-converting enzyme activity, and angiotensins. It has been assumed that these cells also produce angiotensinogen as the substrate of an intracellular renin-angiotensin system. However, measurements of angiotensinogen have not been reported in the neuroblastoma or neuroblastoma-glioma cells, and the possibility that the cells generate angiotensins from fetal bovine angiotensinogen has not been eliminated. In this work angiotensinogen was shown to accumulate in the serum-free medium of thoroughly washed neuroblastoma cells (mouse Neuro-2A and rat B103) and glioma cells (rat C6). Separate experiments demonstrated that mouse Neuro-2A cells continue to produce angiotensinogen even after two passages in a defined serum-free culture medium. Further evidence that the angiotensinogen was not a contaminant from fetal bovine serum was obtained by the use of a monoclonal antibody raised against angiotensinogen of rat plasma. The angiotensinogen of Neuro-2A and C6-glioma cells is bound by the monoclonal antibody, whereas fetal bovine angiotensinogen is not bound. These results are consistent with the hypothesis that angiotensinogen is produced locally in the brain and in neuroblastoma cells as a substrate for an intracellular renin-angiotensin system.

Topics: Angiotensinogen; Angiotensins; Animals; Antibodies, Monoclonal; Astrocytoma; Cell Line; Mice; Neuroblastoma; Rats

Topics: Angiotensinogen; Angiotensins; Animals; Cell Line; Hypothalamus; Neuroblastoma; Radioligand Assay; Rats; Receptors, Angiotensin; Receptors, Cell Surface