Expression of Functional Bradykinin Receptors in Xenopus Oocytes

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Abstract
MRNA prepared from various tissues and cultured cells was injected into Xenopus laevis oocytes. Three to five days after injection, the response of the oocytes to the peptide bradykinin was monitored. The oocytes were voltage clamped and the membrane currents generated on application of agonist were recorded. mRNA from NG108‐15, rat uterus, and human fibroblast cell line WI38 gave similar responses to bradykinin (1 μM), with an initial inward current (10–20 nA) followed by a prolonged period of membrane current oscillations. The same pattern of response was given by total RNA from rat dorsal root ganglia. No response to bradykinin (10 μM) was recorded from oocytes injected with rat brain mRNA, although these oocytes gave peak inward currents of about 75 nA in response to serotonin (10 μM). mRNA from both NG108–15 cells and rat uterus was fractionated on sucrose gradients. This resulted in an approximately fivefold increase in the size of the response compared to that given by unfractionated mRNA. The largest responses were given by mRNA fractions with a size of approximately 4.5 kb. Data were obtained consistent with the expression of both B1 and B2 receptors by WI38 human fibroblasts and with the expression of only the B2 type of receptor by NG108‐15 cells.