Meeting Abstract
104.1 Thursday, Jan. 7 Carbonic anhydrase activity in gill and mantle tissues from Doryteuthis pealeii NYACK, A.C.*; HENRY, R.P.; SEIBEL, B.A.; University of Rhode Island; Auburn University; University of Rhode Island alnyack@gmail.com
The enzyme carbonic anhydrase (CA) rapidly catalyzes the reversible reaction of CO2 to HCO3– and H+ both at sites of production (tissues) and excretion (gills/lungs) in animals. CA is involved in several physiological functions (e.g. energy production, osmoregulation, and acid-base balance), and it is a vital component of the systemic transport and excretion of CO2. Although CA has been examined in many organisms, it has not been characterized in squids. We compared total CA activity between gill segments (anterior, middle, and posterior), mantle, and fin, and within subcellular fractions (membrane, mitochondria, and cytoplasm) from Doryteuthis pealeii. Tissues were homogenized and subjected to differential centrifugation to separate subcellular fractions. CA activity of each fraction was measured using the ∆pH method. Total CA activity was significantly greater in all gill segments than in either mantle or fin (P < 0.001) as was CA activity within each subcellular fraction (P < 0.001). There was no significant difference between gill segments (P = 0.26), or between fin and mantle (P = 0.35). While the cytosolic fraction was significantly greater than other fractions within each tissue type, the mitochondrial fraction was greater than the membrane fraction only in middle and posterior gill segments (P = 0.0015 and 0.0006, respectively). Low CA activity in the fin and mantle (sites of CO2 production) could help facilitate the large Bohr shift in the hemolymph typical of squids. We also hypothesize that the differences between fractions suggest different CA isozymes within each tissue, and differences between gill segment fractions may indicate a shift in predominant functions along the gill from respiratory to osmoregulatory, similar to functional differences observed in crab gills.
