AT1 angiotensin receptors mobilize intracellular calcium in a subclone of NG108-15 neuroblastoma cells.
The effects of angiotensin II (AII) and related peptides on the mobilization of internal Ca2+ were studied in a subclone of NG 108-15 cells. The subclone, C1, was prepared by fluorescence-activated cell cloning using a rapid response kinetics and a large response magnitude following stimulation by AII as the selection criteria. Angiotensin I, AII, and angiotensin III (AIII) stimulated Ca2+ mobilization in the C1 cells in a concentration-dependent manner (1 nM-100 microM), yielding EC50 values of 437 +/- 80 nM (n = 4; slope = 1.6 +/- 0.3), 57 +/- 8 nM (n = 12; slope = 1.5 +/- 0.3), and 36 +/- 5 nM (n = 7; slope = 1.4 +/- 0.3), respectively. AIII was significantly more potent than AII (p less than 0.05). In contrast, Des-Phe8-AII, AII-hexapeptide (AII 3-8), and p-NH2-Phe6-AII (1-10 microM) were inactive as agonists. Although the effects of AII and AIII in C1 and parent NG108-15 cells were totally inhibited by the AT1 receptor-selective nonpeptide antagonist, DUP-753 (0.3-1 microM), the AT2-selective antagonists, EXP-655 and CGP42112A (1-10 microM), failed to block the effects of AII. DUP-753 (0.3-100 nM) produced dextral shifts of the AII-induced concentration-response curves and yielded an estimated affinity constant (pA2) of 8.5 +/- 0.2 (n = 16) using single-point analysis involving different concentrations of DUP-753. These data compared well with those obtained for the inhibition of AII-induced aortic contractions by DUP-753 (pA2 = 8.5) reported previously by others.(ABSTRACT TRUNCATED AT 250 WORDS)
Ransom
J T
JT
Institutes of Immunology and Biological Sciences, Palo Alto, California.
Sharif
N A
NA
Dunne
J F
JF
Momiyama
M
M
Melching
G
G
D000803:Angiotensin I / Q000494:pharmacology; D000804:Angiotensin II / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000805:Angiotensin III / Q000037:antagonists & inhibitors / Q000494:pharmacology; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D001713:Biphenyl Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D007093:Imidazoles / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism*; D019808:Losartan; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology; D011945:Receptors, Angiotensin / Q000378:metabolism*; D013777:Tetrazoles / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D057911:Angiotensin Receptor Antagonists; D001713:Biphenyl Compounds; D007093:Imidazoles; D011945:Receptors, Angiotensin; D013777:Tetrazoles; D000804:Angiotensin II; D000805:Angiotensin III; D000803:Angiotensin I; D019808:Losartan; D002118:Calcium