The Physiology of Blood Trehalose and its Function During Flight in the Blowfly

Abstract

1. The finding (Evans & Dethier, 1957) that glucose and trehalose are the normal blood sugars of the blowfly Phormia regina has been confirmed. 2. It is estimated that most of the flight energy is derived from the oxidation of trehalose and, to a lesser extent, of other sugars found in the blood. 3. Several lines of evidence indicate that the concentration of blood trehalose normally regulates the rate at which energy is expended by the flight muscles during flight. ‘Exhaustion’ results when trehalose cannot be supplied to the flight muscle at the necessary rate. 4. Fat body is the chief source of blood trehalose; endogenous and exogenous substrates are used for its synthesis. The rate of blood trehalose synthesis can be very rapid, almost compensating for the rate of utilization by the flight muscle during flight. 5. It appears, therefore, that the intensity of flight is determined largely by the interaction of two rate processes: the rate of trehalose utilization (flight muscles) and the rate of trehalose synthesis (fat body). 6. A diagram is presented which accounts for the establishment of glucose and trehalose as the normal blood sugars of this fly and summarizes our findings on the transfer of carbohydrates between various tissues. 7. The blood volume (6-7 µl.) has been estimated from dilution of injected 14C-inulin. This volume is not changed appreciably by flight.