NH4C1 and protein metabolism in human gingival fibroblasts

The biologic effect of ammonia was studied in cultures of fibroblasts isolated from human gingiva, NH4Cl in the range 2-20 mM was found to exhibit a concentration dependent growth inhibitory effect, with a delayed action which was most pronounced at low concentrations. Concomitant with the growth inhibitory effect a significant cellular accumulation of protein was evident. No effects on protein synthesis in general, as measured by 14C-proline incorporation, was found, whereas some inhibitory effect on collagen biosynthesis was indicated. Secretion of 14C-collagen and other labeled proteins was not affected. The only pronounced effect of ammonia on metabolism of the 14C-labeled proteins was an inhibition of the intracellular degradation of newly synthesized collagen, the lysosomes being suggested as the site for this degradation.