The neuropeptide bradykinin stimulates phosphoinositide turnover in HSDM1C1 cells: B2-antagonist-sensitive responses and receptor binding studies.
Bradykinin (BK) and its analogs (1 nM-100 microM) stimulated phosphoinositide (PI) turnover in murine fibrosarcoma (HSDM1C1) cells in a concentration-dependent manner. The relative potencies (EC50) were: BK = 48 +/- 4 nM; Lys-BK = 39 +/- 3 nM; Met-Lys-BK = 158 +/- 33 nM, Des-Arg9-BK = 2617 +/- 598 nM (means +/- SEM, n = 3-14). All these analogs were full agonists and they produced up to 5.4 +/- 0.4-fold stimulation of PI turnover at the highest concentration (10-100 microM) of the peptides. In contrast, the analogs [D-Arg0-HYP3-Thienyl5,8-D-Phe7]-BK (HYP3-antagonist), [D-Arg0-HYP3-Thienyl,5,8-D-Phe7]-BK (Thienyl antagonist) and Des-Arg9-Leu8-BK were inactive, as agonists, at 0.1 nM-1 microM in this system. These data suggested that BK-induced PI turnover in these cells was mediated via B2-type of BK receptors. This was confirmed further by the fact that both the B2-selective Hyp3- and Thienyl-antagonists inhibited BK-induced PI turnover with KBS of 369 +/- 51 nM and 368 +/- 118 nM respectively while the B1-selective antagonist, Des-Arg9-Leu8-BK, was inactive at 1 microM. [3H]BK receptor binding studies revealed two binding sites, one with high affinity (Kd = 0.24 +/- 0.06 nM; Bmax = 1.4 +/- 0.4 pmol/g tissue) and the other with low affinity (Kd = 18.5 +/- 0.95 nM; Bmax = 25.1 +/- 0.52 pmol/g tissue), on HSDM1C1 cell homogenates. The rank order of affinity of BK analogs at inhibiting specific [3H]BK binding was similar to that found for PI turnover.(ABSTRACT TRUNCATED AT 250 WORDS)
Sharif
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Institute of Pharmacology, Syntex Discovery Research, Palo Alto, California 94303.
Whiting
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RL
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001920:Bradykinin / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D065168:Bradykinin Receptor Antagonists; D005354:Fibrosarcoma / Q000378:metabolism*; D007609:Kallidin / Q000494:pharmacology; D051379:Mice; D008969:Molecular Sequence Data; D010716:Phosphatidylinositols / Q000378:metabolism*; D018002:Receptors, Bradykinin / Q000378:metabolism*; D014316:Tritium; D014407:Tumor Cells, Cultured
D065168:Bradykinin Receptor Antagonists; D010716:Phosphatidylinositols; D018002:Receptors, Bradykinin; D014316:Tritium; C058532:HOE k86-4321; C024626:bradykinin, des-Arg(9)-; D007609:Kallidin; C018103:bradykinin, Met-Lys-; C053010:NPC 567; D001920:Bradykinin