[en] The rates of ³H-proline incorporation by the rat periodontal ligament, the gingival connective tissue and the dental pulp were studied by autoradiography. The rate of ³H-proline incorporation by the periodontal ligament was 2.8 times higher than by the gingival connective tissue and 5 times higher than by the dental pulp. These differences were significant (p<0.01). The pattern of ³H-proline incorporation by the periodontal ligament was significantly different (p<0.01) from that by the gingival connective tissue and the dental pulp. The latter two tissues exhibited a similar pattern of ³H-proline incorporation. The ratio of the rates of ³H-proline incorporation by the three tissues did not correlate with the ratio of the cellular densities in the same three tissues. (author)