The effects of peptide histidine isoleucine and neuropeptide Y on mucus volume output from the ferret trachea.

1. The effects of peptide histidine isoleucine (PHI) and neuropeptide Y (NPY) were examined on the mucus volume output produced by methacholine and phenylephrine in the ferret whole trachea in vitro. 2. Sustained application of methacholine (5 microM) or phenylephrine (20 microM) produced a maintained volume output of mucus from the trachea. Both these agonists also increased the output of lysozyme (a marker for serous cell secretion). 3. PHI inhibited the maintained mucus volume output produced by methacholine but had no effect on that due to phenylephrine. The output of lysozyme produced by methacholine or phenylephrine was not significantly changed by PHI. 4. NPY enhanced the volume output of mucus produced by methacholine or phenylephrine; however, the rate of output of lysozyme in mucus produced by both agonists was reduced by NPY. 5. We suggest that PHI has no effect on serous cell secretion but inhibits secretion from another source, possibly mucous cells. NPY inhibits serous cell secretion but has a stronger stimulant action on secretion from another source, again possibly mucous cells. 6. PHI and NPY may be important physiological modulators of mucus volume output in the ferret trachea.