Inhibitory effect of NH4Cl on secretion of collagen in human gingival fibroblasts.

The general protein synthesis in human gingival fibroblasts as measured by 14C-proline incorporation was only moderately inhibited by 10 mM NH4C1 during incubation for 36 h. The proportion secreted as noncollagen protein and recovered from the cellular fraction as collagen was not significantly affected, whereas a pronounced inhibitory effect on the secretion of collagen was evident after 24 h. This effect was dose dependent, with a significant inhibition of collagen secretion even at 2 mM ammonia. The applied concentrations of NH4C1 had no significant effect on the hydroxylation of prolyl residues in collagen. Ammonia had no inhibitory effect on the secretion of fibronectin, another major secretory protein from fibroblasts. When comparing different lysosomotropic agents; NH4C1, chloroquine and methylamine, the most prominent effect was consistently found to be an inhibition of the secretion of collagen.