METABOLITES FORMED AFTER INTRAVENOUS ADMINISTRATION OF FREE OR ALBUMIN-BOUND PROSTAGLANDIN El IN THE RAT*

Recent reports [ 1,2] indicated the presence of seven metabolites of prostaglandin Ez (PGE,) and five metabolites of prostaglandin Fzor (PGFZLY) in the urine of rats after intravenous injection with radioactive prostaglandins. These results suggested that PGE, and PGF2, are converted into three groups of metabolites via three separate pathways which involve oxidation of the hydroxyl group at C-15 [3], reduction of the tram double bond [3], B [4] and o oxidations. Previous studies from this laboratory have established the binding in vitro of PGEZ, PGF,, and prostaglandin AZ @‘GA,) to plasma albumin [5,6]. Studies with rats that received intravenous injections of prostaglandin PGFZa and PGAz [7] showed this binding to significantly modify the in vivo metabolism of these prostaglandins as judged from the disappearance of the injected prostaglandins from the blood circulation and the appearance of their metabolites. This report describes differences in the in vivo metabolism of intravenously injected free and albumin-bound PGEz .