Journal of Lipid Research, Vol. 12, 699-705, November 1971
Copyright © 1971 by Lipid Research, Inc.

Differential distribution of orthophosphate-³²P and glycerol-¹⁴C among molecular species of phosphatidylinositols of rat liver in vivo

B. J. Holub and A. Kuksis

Department of Biochemistry, and Banting and Best Department of Medical Research, University of Toronto, Toronto 101, Canada

The incorporation of orthophosphate-³²P and glycerol-2-¹⁴C into the various species of rat liver phosphatidylinositols as a function of time was determined in vivo. ³²P was administered intraperitoneally and glycerol-¹⁴C was given intravenously. The phosphatidylinositols were resolved intact according to degree of unsaturation. 1-3 hr after injection of the labeled phosphate, the relative specific activity of the linoleoyl dienes exceeded that of the arachidonoyl tetraenes about 17-fold, and that of the trienes and polyenes about 8-fold. The relative specific activities of all the fractions became about equal 2-3 days after administration of ³²P.

The labeling patterns obtained with glycerol were comparable to those seen for the phosphate. As early as 5 min about 65% of the activity was localized in the monoenes plus dienes, while only 17% was found in the tetraenes, although the mass proportions of these fractions were 7.1 and 77.0% of the total phosphatidylinositols, respectively. The recovery of the total radioactivity in the monoenes and dienes decreased continuously with time to about 15% at 9 hr, while that recovered in the tetraenes rose steadily to about 70%. The present data are consistent with an active synthesis of the monoenoic and dienoic phosphatidylinositols by way of the phosphatidate, followed by a deacylation-reacylation cycle involving arachidonic acid, as claimed for other rat liver glycerophosphatides.

Supplementary key words arachidonoyl • de novo synthesis • transacylation

Submitted on April 2, 1971
Accepted on June 21, 1971

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