The gene for the human substance P receptor (NK-1) was cloned using cDNA probes made by the polymerase chain reaction from primers based on the rat sequence. The gene spans 45-60 kb and is contained in five exons, with introns interrupting at sites homologous to those in the NK-2 receptor gene. Analysis of restriction digests of genomic DNA from mouse/human cell hybrids indicates the NK-1 receptor is a single-copy gene located on human chromosome 2. Polymerase chain reaction using primers based on the 5' and 3' ends of the coding sequence was used to generate full-length cDNAs from human lung and from IM9 lymphoblast cells. When transfected into COS-7 cells, the NK-1 receptor binds 125I-BHSP with a Kd of 0.35 +/- 0.07 nM and mediates substance P induced phosphatidylinositol metabolism. The receptor is selective for substance P; the relative affinity for neurokinin A and neurokinin B is 100- and 500-fold lower, respectively. Human IM9 lymphoblast cells express relatively high levels of the NK-1 receptor, and Northern blot analysis indicates modulation of mRNA levels by glucocorticoids and growth factors, suggesting that this cell line may be useful as a model for studying the control of NK-1 receptor gene expression.

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1 Mongrel dogs were chronically instrumented with an intra-aortic catheter, a K6nigsberg intraventricular pressure transducer and a D6ppler flow probe around the left coronary artery. After ganglionic blockade with hexamethonium, the cardiovascular effects of bradykinin B, and B2 receptor agonists, des-Arg9-bradykinin and bradykinin (BK), were investigated in the presence and absence of specific antagonists. The contribution of nitric oxide (NO) and prostanoids to the cardiovascular effects of kinins was also examined. 2 BK (1 gg kg-' min-') and des-Arg9-BK (1 Mug kg-' min-') both given as a 2 min i.v. infusion, produced a significant decrease in mean arterial pressure (MAP, -34+4% for BK and -45+2% for des-Arg9-BK) and coronary vascular resistance (CVR, -37+5% for BK and -50+2% for des-Arg9-BK), without affecting cardiac contractility, left ventricular end diastolic pressure, and coronary velocity. BK caused a significantly greater decrease in MAP and CVR than des-Arg9-BK (P<0.05). 3 Pretreatment with the B, receptor antagonist, des-Arg9-[Leu8]-BK (25 pg kg-') significantly inhibited the decrease in MAP and CVR produced by des-Arg9-BK but not by BK. Infusion of des-Arg9-[Leu8]-BK alone also induced a significant decrease in MAP and CVR (P<0.05). In the presence of the B2 receptor antagonist, Hoe 140 (25 jug kg-'), only the decreases in MAP and CVR caused by BK were significantly reduced (P<0.05). 4 Inhibition of NO synthase with Nw-nitro-L-arginine (L-NOARG, 45 mg kg-') significantly (P<0.05) prevented the decrease in CVR but not MAP induced by des-Arg9-BK, whilst responses to BK were not affected by L-NOARG pretreatment. Inhibition of prostanoid synthesis with indomethacin (25 mg kg-') did not affect the reductions in MAP and CVR induced by des-Arg9-BK or BK. 5 In conclusion, i.v. des-Arg9-BK and BK administration induced reductions in MAP and CVR suggesting that in conscious instrumented dogs both B, and B2 receptors are present and can affect systemic blood pressure and coronary resistance regulation. Our results also suggest that prostanoids are not involved in the vascular response to kinins and that coronary vascular B, receptors are at least in part coupled to the release of NO.