Angiotensin II potentiates DNA synthesis in AT-1 transformed cardiomyocytes.
Angiotensin II has been shown to be mitogenic in various cell types. In cultured neonatal cardiomyocytes, we have demonstrated that angiotensin II causes hypertrophy, not hyperplasia. However, fetal or neonatal cardiomyocytes exhibit limited proliferation in primary culture, and are mitotically less potent. In order to determine whether angiotensin II is simply a hypertrophic or hyperplastic growth factor for mitotically-potent cardiomyocytes, we analysed [3H]-thymidine uptake and cell cycle-regulated gene expression using SV40 large T-transformed AT-1 cardiomyocytes. Angiotensin II, alone and in combination with other growth factors, increased [3H]-thymidine uptake in a dose-dependent manner. The mRNA expression of G1 cyclins (Cyclin C, D1, D2, D3) and histone H1-kinase activity by CDK2 increased 6 h after angiotensin II stimulation. Western blot analysis revealed cyclin B1 expression after 18 h , which peaked at 30 h. Histone H1-kinase activity by cdc2 was also increased by angiotensin II, and peaked at 24-36 h, indicating that these changes were cell cycle dependent. Double immunofluorescent photography showed that AT-1 cells incorporated BrdU, and expressed cdc2 by angiotensin II stimulation. [3H]-thymidine and BrdU uptake were blocked by losartan, but not by PD123319. In contrast with neonatal cardiomyocytes, angiotensin II potentiated DNA synthesis and induced cell cycle regulated gene expression in AT-1 cardiomyocytes, and this activity was mediated by the angiotensin II type-1 receptor.
Fukuda
K
K
Cardiovascular Division, Beth Israel Deaconess Medical Center, and Department of Medicine, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, USA.
Izumo
S
S
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects; D002461:Cell Line, Transformed; D019926:Cyclin B / Q000235:genetics; D056744:Cyclin B1; D016213:Cyclins / Q000235:genetics; D004261:DNA Replication / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D019808:Losartan / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D009206:Myocardium / Q000166:cytology*; D010766:Phosphorylation; D006656:Protamine Kinase / Q000235:genetics; D011725:Pyridines / Q000494:pharmacology; D013539:Simian virus 40; D013936:Thymidine / Q000378:metabolism; D014407:Tumor Cells, Cultured
D000952:Antigens, Polyomavirus Transforming; C534700:Ccnb1 protein, mouse; D019926:Cyclin B; D056744:Cyclin B1; D016213:Cyclins; D007093:Imidazoles; D011725:Pyridines; D000804:Angiotensin II; C073402:PD 123319; D006656:Protamine Kinase; D019808:Losartan; D013936:Thymidine