Beschreibung:
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<jats:list-item><jats:p>Cultured arterial smooth muscle cells synthesize and secrete two types of sulfated proteoglycans, designated as proteoglycan A and B, into the culture medium. They are isolated as immunologically distinct monomers with relative molecular masses of 280 × 10<jats:sup>3</jats:sup> and 180 × 10<jats:sup>3</jats:sup> and are characterized as chondroitin‐sulfate‐rich (A) and dermatan‐sulfate‐rich (B) proteoglycans. Both proteoglycan A and B were labelled with [<jats:sup>35</jats:sup>S]sulfate and used for studies of endocytosis.</jats:p></jats:list-item>
<jats:list-item><jats:p>Uptake of proteoglycan B by arterial smooth muscle cells shows saturable kinetics. At saturation (500 μ) one cell may endocytose up to 1.5 × 10<jats:sup>6</jats:sup> proteoglycan B molecules/h. Proteoglycan A is internalized at a 10‐fold lower rate. No saturation kinetics were observed at high proteoglycan A concentrations (500 μ).</jats:p></jats:list-item>
<jats:list-item><jats:p>Endocytosis of proteoglycan B in the presence of an excess of proteoglycan A and vice versa suggest that proteoglycan A and B do not compete for the same receptor site. Free hyaluronate or chondroitin sulfate do not inhibit the uptake of proteoglycan B or A.</jats:p></jats:list-item>
<jats:list-item><jats:p>The results suggest that proteoglycan B is internalized by arterial smooth muscle cells via a high‐affinity receptor‐mediated process, whereas proteoglycan A is taken up by fluid endocytosis and/or by low‐affinity endocytotic processes.</jats:p></jats:list-item>
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