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GLYCEROL-3-PHOSPHATE ACYLTRANSFERASE 2 EXPRESSION CORRELATES WITH TRIACYLGLYCEROL MASS IN RAT TESTISPellon Maison|||M1; Cattaneo|||ER1; Coleman |||RA2; Gonzalez Baro|||MR1 1INIBIOLP- UNLP- CCT La Plata CONICET- 60 y 120 La Plata. 2Dept Nutrition, Univ. N. Carolina, USA E-mail: magalipellon@yahoo.com.ar Polyunsaturated fatty acids (PUFA) play an important role in testicular metabolism. It has been suggested that PUFA-rich triacylglycerols (TAG) play a special role in the traffic and metabolism of PUFA in testis. Glycerol-3-P acyltransferases (GPAT) catalyze the first and committed step in de novo glycerolipid synthesis. The mitochondrial isoform GPAT2 is highly expressed in rat testis and has no preference for saturated acyl-CoA substrates. We have previously shown by Oil-red-O staining that GPAT2 overexpression in CHOK1 cells increased the TAG content compared to GPAT1-overexpressing and control cells. To correlate gpat2 expression with TAG synthesis in testis, we measured TAG mass and gpat2 mRNA and protein expression during postnatal development. Testicular 30-day old rat TAG mass was 2-fold higher than 19, 40 and 60-day old rats. Interestingly, gpat2 mRNA expression followed the same pattern, reaching a peak at 30 days of age, consistent with GPAT2 protein expression. NEM sensitive GPAT activity was measured in purified mitochondria with palmitoylCoA and oleoylCoA substrates. This activity did not change at different stages of development when palmitoylCoA was used as a substrate but reached a peak at 40 days of age when oleoylCoA was used.Our results suggest that GPAT2 is involved in TAG synthesis in testis and that its activity is important for the onset of spermatogenesis. Biocell 33, 87. ISSN 0327-9545