THE IN-VITRO RESPIRATORY AND ACID-BASE PROPERTIES OF BLOOD AND TISSUEFROM THE KEMPS RIDLEY SEA-TURTLE, LEPIDOCHELYS-KEMPI

We determined the in vitro respiratory and acid-base properties of blo od and tissue from Kemp's ridley sea turtles (Lepidochelys kempi). Blo od O-2 dissociation curves of ridley turtles were sigmoid, with a P-50 of 31.2 +/- 0.3 (mean +/- SD) torr. at 25 degrees C and pH 7.51. Incr ements in temperature or PCO2 were associated with a shift of the O-2 dissociation curves to the right and, hence, a reduction in hemoglobin -O-2 binding affinity. The apparent heat of oxygenation, which is a me asure of the temperature sensitivity of hemoglobin-O-2 affinity, was - 10.5 kcal/mol O-2. The degree of cooperativity of O-2 for hemoglobin b inding sites, as measured by the Hill coefficient, increased at higher temperatures (20-30 degrees C at a PCO2 of 37 torr), but was unaffect ed by changes in PCO2 (37-52 ton at 25 degrees C). The CO2-Bohr effect was -0.34 torr/pH unit. The CO2 capacitance coefficient of whole bloo d and plasma declined as a function of increased PCO2 (22 degrees C). Non-bicarbonate buffer capacities (22 degrees C) were 19.7, 18.5, and 6.4 slykes for whole blood, true plasma, and separated plasma, respect ively. The skeletal muscle myoglobin content was 3.1 +/- 0.84 mg.g(-1) of tissue. The respiratory and acid-base properties of blood and tiss ue from Kemp's ridley sea turtles are consistent with those of species that utilize lung O-2 stores during long-term aerobic dives. The enha nced hemoglobin-O-2 temperature sensitivity exhibited by the ridley tu rtle could be a physiological adaptation for life in coastal environme nts that typically undergo substantial fluctuations in temperature.