Studies of differential turnover of palmitoyl and stearoyl species of glycerophosphatides using labeled unsaturated acids |
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Authors: | B J Holub W C Breckenridge A Kuksis |
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Affiliation: | (1) Department of Biochemistry and Banting and Best Department, of Medical Research, University of Toronto, Toronto, Canada |
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Abstract: | Normal and bile fistula rats were injected with 1-14C-linoleate and arachidonate as albumin complex and the glycerides and glycerophosphatides of the liver and bile were isolated
at various time intervals. The distribution of radioactivity among the individual molecular species was determined by thin
layer and radio gas chromatography and specific enzymic hydrolyses. At 30 min after administration of linoleate 30% of the
radioactivity in liver was in lecithins and 8% in cephalins, while at 120 min 48% was in lecithins and 16% in cephalins. After
arachidonate, 58% and 64% of the counts were in lecithins and 12% to 13% in the cephalins at the above periods of sampling.
The specific activity of the palmitoyl linoleoyl lecithins and cephalins was two to three times higher than that of the corresponding
stearoyl linoleoyl species, which was of the same order but much lower magnitude than found previously for lecithins using
labeled phosphate and choline. The palmitoyl and stearoyl species of arachidonoyl lecithins possessed equal specific activities,
in sharp contrast to previous findings with radioactive phosphate, which showed a 12 times higher specific activity for the
palmitoyl arachidonate. The palmitoyl arachidonoyl cephalins had two to three times greater specific activity than the corresponding
stearoyl species in agreement with previous work using labeled phosphate. The distribution of radioactivity suggests that
the arachidonate was incorporated into the lecithins largely via acyl transfer, while the linoleate contributed to both acyl
transfer and de novo synthesis. Interpretation of the mechanism of uptake of these acids into the cephalins awaits further
studies.
Presented in part at the Federation of American Societies for Experimental Biology Meeting, Atlantic City, April 1970. |
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