EFFECTORS OF METABOLIC DEPRESSION IN AN ESTIVATING PULMONATE SNAIL (HELIX-ASPERSA) - WHOLE ANIMAL AND IN-VITRO TISSUE STUDIES

We have examined metabolic depression in the land snail (Helix aspersa ) during estivation, and have developed a tissue model of metabolic de pression using an in vitro mantle preparation. The metabolic rate of H . aspersa is depressed by 84% in vivo within 4 weeks of onset of estiv ation, and this metabolic depression is accompanied by a decrease in h aemolymph PO2 and pH, and an increase in haemolymph PCO2. The in vitro mantle preparation has a stable O-2 consumption and energy charge, an d an energy charge similar to that of mantle in vivo. The in vitro man tle is an O-2-conforming tissue, with VO2 varying curvilinearly with P O2. Consequently, we have developed a mathematical method of calculati ng tissue VO2 at any PO2. These calculations show that under appropria te incubation conditions of pH and PO2, the mantle from estivating ani mals shows a stable in vitro metabolic depression of 48% compared to m antle from control snails. The extrinsic effects of PO2 and pH account for 70% of the total in vitro metabolic depression of mantle tissue; intrinsic effecters contribute a further 30%.