Polyethylene glycol-L-asparaginase and L-asparaginase studies in rabbits.
Injections of polyethylene glycol (PEG)-L-asparaginase or L-asparaginase were given to two rabbits each at doses of 40 units/kg. Ten min following injection of either enzyme preparation, the plasma enzyme concentration was approximately 1 unit/ml. This level decreased steadily in the rabbits given L-asparaginase, with a t1/2 of approximately 20 hr. In contrast, the enzyme level in rabbits given PEG-L-asparaginase decreased much more slowly, with a t1/2 of approximately 144 hr. The slower disappearance rate of PEG-L-asparaginase resulted in greater values for the area under the concentration versus time curve and smaller values for total clearance. Immediately following the enzyme injections, no L-asparagine could be detected in the plasma, and a transient elevation of L-aspartic acid levels was noted. By 4 hr, the L-aspartic acid level in all of the rabbits returned to near normal. The L-asparagine, however, was not measurable as long as plasma enzyme was detectable. Levels of L-asparagine returned to normal 4 days after L-asparaginase administration, and 27 days elapsed before L-asparagine was detected in rabbits given PEG-L-asparaginase.
D000596:Amino Acids / Q000097:blood; D000818:Animals; D001215:Asparaginase / Q000097:blood / Q000493:pharmacokinetics*; D001216:Asparagine / Q000097:blood; D001224:Aspartic Acid / Q000097:blood; D006207:Half-Life; D066298:In Vitro Techniques; D008297:Male; D011092:Polyethylene Glycols / Q000097:blood / Q000493:pharmacokinetics*; D011817:Rabbits
D000596:Amino Acids; D001224:Aspartic Acid; D011092:Polyethylene Glycols; D001216:Asparagine; C042705:pegaspargase; D001215:Asparaginase