Bradykinin induces a rapid release of inositol trisphosphate from a neuroblastoma hybrid cell line NCB-20 that is not antagonized by enkephalin

Abstract

In mouse neuroblastoma × Chinese hamster brain clonal cell line NCB-20, bradykinin (BK) receptor stimulation causes phosphoinositide hydrolysis and release of inositol phosphates. Maximum stimulation (4-fold) of [2- 3H]inositol trisphosphate (IP 3) release in the absence of Li + from NCB-20's prelabelled for 20–24 hours with [2- 3H]myo-inositol (15 μCi/confluent 60 mm dish) occurred after 5–10 seconds of bradykinin exposure, with an EC 50 of approximately 100 nM. Inositol bisphosphate (IP 2) and inositol monophosphate (IP 1) also showed increases (2.9-fold and 1.5 fold, respectively), with peaks at 15–20 seconds and 50 seconds, respectively. Under these same conditions, D-Ala 2-D-Leu 5 enkephalin (DADLE) (10 μM), an opiate agonist with 2 nM affinity, gave no stimulation of IP 3 release. Furthermore, it did not block BK-initiated release, both when applied simultaneously with BK and when cells were preincubated with DADLE for 100 minutes to lower cyclic AMP levels. These results show that (1) pain-inducing BK has a major acute stimulatory effect on receptor-phospholipase C-coupled IP 3 release, (2) the opioid peptide DADLE has no such effect and (3), DADLE does not block the IP 3 release induced by BK.