Turnover of locust haemolymph diglycerides during flight and rest

Abstract

The constant, elevated diglyceride concentration in the haemolymph of adult male Locusta migratoria during sustained tethered flight (14.1 ± 1.2 mg/ml haemolymph) was established to be a steady state, in which the rate of diglyceride mobilization matched the rate of utilization. Pulse-labelling of the haemolymph diglycerides with [1- 14C]-oleic acid in steady state flight conditions results in a turnover time of about 1 hr for the diglyceride pool, whereas in animals rested after flight values close to 8 hr were obtained. So, during flight there is a sharp increase in lipid transport, the initial turnover rate in the resting animal (0.3–0.5 mg diglyceride/hr) reaching 3.4 mg diglyceride/hr at the steady state flight level. As identical turnover rates were obtained using [1- 14C]-palmitic acid or [1- 14C]-linolenic acid, apparently there is no preferential utilization of diglycerides with a specific fatty acid composition in flight muscle energy metabolism. The characteristic diglyceride fatty acid spectrum at the steady state flight level remained remarkably constant during flight performances lasting for 6 hr. The above findings indicate homogeneity of the haemolymph diglyceride pool and suggest random utilization of fatty acids.