5-Hydroxytryptamine, angiotensin and bradykinin transiently increase intracellular calcium concentrations and PKC-alpha activity, but do not induce mitogenesis in human vascular smooth muscle cells.
The potent vasoconstrictor substances, 5-hydroxytryptamine (5-HT), angiotensin II (A II), and bradykinin bind to G-protein coupled receptors and activate phospholipase C-beta. Using the Fura-2 technique and microfluorometry we found that all three agonists induce a transient increase in intracellular calcium ([Ca2+]i) by releasing stored calcium in human renal artery smooth muscle cells. Using binding of [3H]-phorbol dibutyrate (PDBu) to quantify membrane-associated protein kinase C (PKC) we also showed that 5-HT, A II and bradykinin induced a rapid but transient translocation of protein kinase C (PKC) to the plasma membrane. The time-course of the rise in [Ca2+]i was similar to that of the increase in [3H]-PDBu binding, suggesting transient activation of the calcium dependent alpha-isoform of PKC. Following prolonged pre-treatment with tetradecanoyl phorbol acetate (100 nmol L-1), which down-regulates PKC-alpha and delta, the angiotensin-induced PKC translocation was lost. 5-HT, A II or bradykinin were unable to increase cell proliferation or act as a co-mitogens with platelet-derived growth factor in human vascular smooth muscle cells. Thus, transient increases in [Ca2+]i or PKC activity by a vasoconstrictor agent are insufficient to cause vascular smooth muscle proliferation.
Assender
J W
JW
Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
Irenius
E
E
Fredholm
B B
BB
D000804:Angiotensin II / Q000494:pharmacology*; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D006801:Humans; D008938:Mitosis / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D012701:Serotonin / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism; D014665:Vasodilator Agents / Q000494:pharmacology*
D010982:Platelet-Derived Growth Factor; D014665:Vasodilator Agents; D000804:Angiotensin II; D012701:Serotonin; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D001920:Bradykinin; D002118:Calcium; D013936:Thymidine