Incorporation of [U-14C] palmitate into lipids by the stable fly, Stomoxys calcitrans (L.)

The incorporation in vivo of [U-14C] palmitate into fat body lipids was studied in the blood feeding stable fly, Stomoxys calcitrans. Palmitate was rapidly esterified into triacylglycerol and after one-half h, nearly one third of the total recovered label was in the triacylglycerol fraction with a concomitant loss of radioactivity in the free fatty acids. The fat body, from one day sugar-water-fed flies incorporated more label into triacylglycerol than those from flies fed on blood. The present study indicates that fat body from sugar-water-fed stable flies retains a high lipogenic ability and that availability of proper precursors may be a limiting factor in lipogenesis. The incorporation of [14C] palmitate into triacylglycerol decreased during subsequent blood meals, except for an increased incorporation into triacylglycerol by the fat body of males after the fourth blood meal. Flies fed five blood meals showed the least incorporation of label into fat body lipids after [14C] palmitate injection. The capacity for incorporation of [14C] palmitate into fat body lipids was reduced in starved stable flies. In addition, the lipids isolated from starved flies showed reduced specific activities.