Sodium spirulan (Na-SP) is a sulfated polysaccharide isolated from the blue-green alga Spirulina platensis. Na-SP has anticoagulant and fibrinolytic properties in vitro, including activation of heparin cofactor II, enhancement of vascular endothelial cell fibrinolytic activity and stimulation of endothelial proteoglycan (PG) release. In the present study, we investigated the types of endothelial PGs whose release is stimulated by Na-SP. Na-SP stimulated the PG release in a dose- and time-dependent manner. However, heparin, dextran sulfate and hyaluronan stimulated the release of heparan sulfate PGs rather than chondroitin/dermatan sulfate PGs, whereas the release of both types of PGs was strongly stimulated by Na-SP. Sepharose CL-6B chromatography of [35S]sulfate-labeled PGs showed that PGs were partially released after partial degradation of the core proteins without a change in chain length of the glycosaminoglycan chains after Na-SP treatment. On the other hand, SDS-polyacrylamide gel electrophoresis and Western blot analysis of the PG core proteins indicated that the Na-SP-releasable PGs are both a large heparan sulfate PG, perlecan, and a small chondroitin/dermatan sulfate PG, biglycan, without change in the size of the core proteins. Taken together, these results suggest that Na-SP stimulates the endothelial release of both perlecan and biglycan with the intact structures, possibly by mechanisms different from those of heparin, dextran sulfate and hyaluronan; a part of the PG core proteins may be degraded after Na-SP treatment. Since perlecan and biglycan have antithrombin activities, the present data support the hypothesis that Na-SP may enhance local anticoagulant activity in the liquid phase on the endothelium via stimulation of endothelial PG release.