Meeting Abstract
P2.131 Sunday, Jan. 5 15:30 Effects of environmental hypoxia and elevated CO2 on the hemocyanin oxygen binding properties of the Atlantic mud crab, Panopeus herbstii MILLAN-HERNANDEZ, CA*; BURNETT, KG; BURNETT, LE; College of Charleston; College of Charleston; College of Charleston c_millan.01@hotmail.com
The changes in hemocyanin (Hc) O2 binding properties with exposure to chronic environmental hypoxia and hypercapnia were investigated in the Atlantic mud crab. Crabs (mean wt. 5.31 g) were exposed to one of four treatments for 2 weeks: normoxia (>80% air saturation), hypoxia (20% air saturation), hypercapnia (2% CO2, > 80% air saturation), and hypercapnic hypoxia (2% CO2, 20% air saturation). Hemocyanin concentration in crabs freshly collected from the field was 5.9 g/100 mL ±0.6 SEM, N = 29; this did not change as a result of treatment. Hc of normoxic controls displayed a Bohr shift with a slope of -0.51 and a P50 of 1.47 kPa at pH 7.4. Hypoxia did not change the size of the Bohr shift, but resulted in an overall increase in O2 affinity (P50 = 1.29 kPa, pH 7.4). The addition of CO2 resulted in a larger Bohr shift (-0.66) compared to the normoxic control. Treatment with a combination of hypoxia and CO2 also increased the Bohr shift (-0.61) compared with its hypoxia control (-0.47). Neither CO2 treatment increased the O2 affinity. The interaction between the O2 binding sites on Hc, cooperativity (=n50), was not influenced significantly by pH in normoxia and hypoxia with the mean n50 of 3.2 at pH 7.4. n50 decreased with pH in the two CO2 treatments and was 2.9 at pH 7.4 in both treatments. There was a small effect of lactate in the normoxia treatment (-0.07 = Δlog P50/Δlog [lactate]) at pH 7.4 and there was no significant change with any treatment. Hc was insensitive to urate. P. herbstii Hc O2 affinity clearly increased as a result of chronic treatment with hypoxia. However, environmental CO2 canceled the adaptive benefits of the hypoxia treatment, especially at low pH. (NSF DBI-1062990, IOS-1147008)
