LACTATE ACCUMULATION IN THE SHELL OF THE TURTLE CHRYSEMYS-PICTA BELLII DURING ANOXIA AT 3-DEGREES-C AND 10-DEGREES-C

Lactate concentrations were measured in the shell and plasma of the tu rtle Chrysemys picta bellii after 3 months of submergence anoxia at 3 degrees C and during and after 9 days of submergence anoxia at 10 degr ees C. Liver and skeletal muscle lactate levels were also measured in control and anoxic animals at each temperature, At 3 degrees C, mean s hell lactate concentration (N=4) reached 133 mmol kg(-1) shell mass an d plasma lactate levels were 144 mmol l(-1); at 10 degrees C, shell an d plasma lactate concentrations (N=5) rose in parallel during anoxic e xposure, to 70.8 mmol kg(-1) shell mass and 78.9 mmol l(-1), respectiv ely, and returned in parallel to control levels during 9 days of recov ery, At the end of the anoxic periods, an estimated 44% of the total b ody lactate resided in the shell at 3 degrees C and 43% at 10 degrees C, and indirect evidence suggests that the shell buffered these same f ractions of the acid load, Because of the high lactate concentration p er kilogram of shell water (416 mmol kg(-1) at 3 degrees C; 221 mmol k g(-1) at 10 degrees C) and the known formation of calcium lactate comp lexes, it is postulated that most of the lactate existed in the shell in combined form. I conclude that sequestration of lactate within the shell represents a potentially major adaptation to anoxic acidosis for this animal and, together with the previously described release of sh ell carbonates, may account for up to two-thirds of the total lactic a cid buffering in this animal.