ISSN:
1573-6903
Keywords:
Bradykinin
;
receptors
;
phosphoinositides
;
PI turnover
;
receptor binding
;
HSDM1C1 cells
;
fibrosarcoma
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Bradykinin (BK) and its analogs (1 nM-100 μM) 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 μM) 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 μM 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 μM. [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. Taken together, these data have provided evidence for the presence of two B2-type BK binding sites on the HSDM1C1 cells. Based on the affinity parameters, the low-affinity component of [3H]BK binding in HSDM1C1 cells appears to be coupled to the phospholipase C-induced PI turnover mechanism. The high-affinity component has been previously shown to mediate the production of prostaglandins by activation of phospholipase A2.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00975053
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