Changes in proteoglycan composition during development of rat skin. The occurrence in fetal skin of a chondroitin sulfate proteoglycan with high turnover rate.

Extraction of the skin of newborn rat yielded two populations of galactosaminoglycan-containing proteoglycan: a Mr = 111,000-200,000 dermatan sulfate proteoglycan (DS-PG) with a Mr congruent to 55,000 core glycoprotein and a Mr congruent to 10(6) chondroitin sulfate proteoglycan (CS-PGs) composed of two subpopulations with different size core-glycoproteins (Mr congruent to 480,000 and 520,000). Tryptic peptide mapping of chondroitinase-treated DS-PG and CS-PGs indicated that the peptide patterns observed with the two core molecules from CS-PGs were identical with each other but distinct from the peptide pattern of the DS-PG core molecule. It is likely therefore that the two forms of CS-PGs are derived from the same gene product by post-translational modification or partial degradation, but DS-PG is derived from a distinct gene product. Comparison of the concentration (hexuronate/DNA) of the proteoglycans in newborn and fetal rat skin showed an age-related change in proteoglycan composition; at 4 days before birth, the uronic acid proportions, DS-PG:CS-PGs, were about 14:1 and during the next 4 days, DS-PG increased 2.2-fold whereas CS-PGs decreased 4-fold. On a per DNA basis, the rate of [3H]serine incorporation into CS-PGs was 2.5 times the rate for DS-PG at 4 days before birth but decreased by 95% during the next 4 days. The rate for DS-PG also decreased but to a much lesser extent, so that by 2 days before birth, it began to exceed the rate for CS-PGs. The striking change in the concentration and labeling rate of CS-PGs can be interpreted either as a decrease of CS-PGs synthesis, or as an increase of CS-PGs breakdown, or both, a process which might be involved in the transition of extracellular matrix from a fetal type to a newborn or adult type.