In:
Canadian Journal of Physiology and Pharmacology, Canadian Science Publishing, Vol. 70, No. 10 ( 1992-10-01), p. 1360-1371
Abstract:
Primary cultures of cells from late pregnant rat myometrium contain B2 kinin receptors through which bradykinin (BK) stimulates inositol phosphate (InsP) formation and arachidonic acid (20:4) release. Equilibrium binding at 4 °C revealed that [ 3 H]BK identified a maximal number of cell surface B2 kinin receptor binding sites on rat myometrial cells of 308 ± 78 fmol/10 6 cells with apparently a single equilibrium dissociation constant of 1.8 ± 0.2 nM. At 37 °C, [ 3 H]BK binding was associated with a time-dependent decrease in the reversibility of the binding. This decrease was due in part to formation of slowly dissociating cell surface receptor [ 3 H]BK binding and in part to internalization of the receptor-bound [ 3 H]BK. Exposure of labeled cells to BK resulted in dose-dependent increases in [ 3 H]InsP 3 , [ 3 H]InsP 2 ([ 3 H]Ins(1,4)P 2 ), and [ 3 H]InsP 1 [([ 3 H]Ins(1)P 1 ) formation and [ 3 H]20:4 release. Pretreatment with 100 ng/mL pertussis toxin did not perturb BK stimulation of [ 3 H]InsP formation but partially (~30%) inhibited BK stimulation of [ 3 H]20:4 release. BK stimulation of [ 3 H]20:4 release was directly proportional to the number of receptor sites occupied by BK. In contrast, stimulation of [ 3 H]InsP formation required a threshold level of receptor occupancy, which decreased as a function of time of BK exposure. These results show that BK interacts with B2 kinin receptors on rat myometrial cells with apparently a single affinity through which BK stimulates [ 3 H]InsP formation and [ 3 H]20:4 release. BK stimulation of [ 3 H]InsP formation requires a threshold BK concentration, which decreases with time, and we suggest that the decrease is due to a time-dependent formation of a BK receptor binding state from which BK slowly dissociates.Key words: bradykinin, receptors, myometrium, inositol phosphates, arachidonic acid.
Type of Medium:
Online Resource
ISSN:
0008-4212
,
1205-7541
Language:
English
Publisher:
Canadian Science Publishing
Publication Date:
1992
detail.hit.zdb_id:
2004356-9
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