Several physiological effects induced by activation of neurokinin3 (NK3) receptors are mediated by the production of nitric oxide (NO). We investigated the intracellular coupling of NK3 receptors to NO synthase (NOS) using a Chinese hamster ovary cell line that was stably transfected with both the NK3 receptor and type I (neuronal) NOS. NOS activity in the transfected cell line was assayed directly, by measuring the formation of L- citrulline, another product of NOS, as well as indirectly, by measuring the production of cGMP in cultured rat fetal lung fibroblasts (RFL-6 cells). MePhe7-neurokinin B (NKB) stimulation of L-[3H]citrulline production was concentration-dependent and yielded a two-site model for the concentration- response relationship. The production of L-citrulline in response to two other tachykinins, substance P or neurokinin A, revealed only a one-site nature of the response. The production of cGMP in response to MePhe7-NKB had an EC50 value that corresponded to the high-potency component of MePhe7- NKB-induced production of L-[3H]citrulline. Agonist-induced calcium signaling was also concentration-dependent, and the acute increase in the production of cGMP by MePhe7-NKB (0.1 nM) was dependent on the release of calcium from intracellular stores. Results of this study provide the first direct evidence that NK3 receptors couple to the generation of NO within the same cell.
|Number of pages
|Journal of Pharmacology and Experimental Therapeutics
|Published - May 2000
ASJC Scopus subject areas
- Molecular Medicine