Soluble (1-->3)-beta-D-glucan purified from Candida albicans: biologic effects and distribution in blood and organs in rabbits.

(1-->3)-beta-D-glucan is a ubiquitous constituent of fungi, and elevated plasma glucan levels are commonly present in patients with deep mycosis or fungemia. The pharmacokinetics, biologic effects, and distribution in blood and organs of iodine 125-labeled (1--> 3)-beta-D-glucan purified from Candida albicans organisms were analyzed in rabbits during the 24-hour period after intravenous administration of this constituent. The intravascular half-life of beta-glucan was 1.8 minutes in the low-dose group (9.3 micrograms/kg, n = 3) and 1.4 minutes in the high-dose group (222 micrograms/kg, n = 3), and the total body clearance was 1.12 +/- 0.30 ml/min and 1.17 +/- 0.16 ml/min (mean +/- SD), respectively (not significantly different). The serum concentration of (1-->3)-beta-D-glucan was also biologically determined by a test using coagulation factor G of the Japanese horse-shoe crab (G test). There was good correlation between the clearance of beta-glucan measured biologically and isotopically. During the 24-hour period of observation the rabbits remained well and beta-glucan failed to alter blood cell counts, tumor necrosis factor levels, or lipid metabolism. 125I-labeled beta-glucan associated with the blood cellular compartment initially was less than 3% (the majority in the platelets) and decreased further during the following 2-hour period. Over 97% of circulating 125I-labeled beta-glucan was associated with the cell-free plasma, and the majority of this glucan in plasma appeared not to be associated with lipoproteins. The liver contained more than 80% of the 125I-labeled beta-glucan detected in the six major organs analyzed.