Tachykinins induce a [Ca2+]i rise in the acinar cells of feline tracheal submucosal gland.

The intracellular Ca2+ concentration ([Ca2+]i) of acinar cells of isolated submucosal glands from trachea was measured using a fluorescent dye, Fura-2. Neurokinin A (NK-A) produced a sustained rise in [Ca2+]i in a dose-dependent manner, reaching a response of 500 to 600% of the prior baseline value at 10(-6) or 10(-5) M, and the NK-A evoked [Ca2+]i was significantly higher than that by substance P (SP) at similar concentrations. NK-B did not induce significant increases in [Ca2+]i. In a Ca(2+)-free solution, NK-A produced a transient rise in [Ca2+]i, which returned to the baseline within 3 min. Mucus glycoprotein (MGP) secretion, estimated by measuring trichloroacetic-acid (TCA) precipitable glycoconjugates, was stimulated by NK-A or SP. These findings indicate that tachykinins produce a rise in [Ca2+]i by both entry from the extracellular solution and release from intracellular storage, probably by NK-2 receptor stimulation, and stimulate MGP secretion from airway submucosal glands.