The bradykinin receptor--a putative receptor-operated channel in PC12 cells: studies of neurotransmitter release and inositol phosphate accumulation.
Bradykinin (BK) induced [3H]norepinephrine [( 3H]NE) release and phosphatidylinositol turnover were investigated in PC12 cells. Induction of [3H]NE release by BK is mediated by activation of BK-B2-receptors, as determined using type specific BK receptor antagonists. BK induces [3H]NE release with a half maximal effective concentration of 30 +/- 0.5 nM, and reaches maximal net fractional release of 9.0 +/- 1% with 200 nM BK. The BK-induced release is Ca2+ dependent, reaching maximal release at 1.0 mM Ca2+, is pertussis toxin insensitive (1 microgram/ml), slightly increased by a dibutyryl cAMP (1 mM) and not affected by inhibitors of the cyclooxygenase or lipoxygenase pathways. Voltage-sensitive Ca2+ channel blockers, verapamil (10 microM), nifedipine (10 microM), and omega-conotoxin (CgTx 10 nM), do not block the BK-induced release. However, a considerable inhibitory effect was obtained by divalent cations Co2+ (ED50 = 0.2 mM) and Ni2+ (ED50(2)+ = 1 mM). These results indicate the involvement of a Ca2+ channel in the BK-mediated release which is different from the L- or N-type voltage sensitive calcium channels. Whereas [Ca2+]ex is essential for the BK-induction of catecholamine release, the rise in level of InsP's induced by BK in the presence or in the absence of [Ca2+]ex is similar up to concentration of 1 microM. This indicates that the rise in InsP's induced by BK is not sufficient to cause neurotransmitter release. Moreover, subsequent addition of Ca2+ to BK-stimulated cells in Ca(2+)-free medium yields no release. Hence, no activity triggered by BK alone could be further stimulated by Ca2+ for induction of release.(ABSTRACT TRUNCATED AT 250 WORDS)
Weiss
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Department of Biological Chemistry, Hebrew University of Jerusalem, Israel.
Atlas
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D000310:Adrenal Gland Neoplasms; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002460:Cell Line; D000242:Cyclic AMP / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004815:Epidermal Growth Factor / Q000494:pharmacology; D007294:Inositol / Q000378:metabolism; D007295:Inositol Phosphates / Q000378:metabolism; D007700:Kinetics; D009638:Norepinephrine / Q000378:metabolism*; D010673:Pheochromocytoma; D051381:Rats; D018002:Receptors, Bradykinin; D017981:Receptors, Neurotransmitter / Q000502:physiology*
D002121:Calcium Channel Blockers; D007295:Inositol Phosphates; D018002:Receptors, Bradykinin; D017981:Receptors, Neurotransmitter; D007294:Inositol; D004815:Epidermal Growth Factor; D000242:Cyclic AMP; D001920:Bradykinin; D002118:Calcium; D009638:Norepinephrine