Meeting Abstract
P1.86 Jan. 4 Salinity-stimulated changes in expression and activity of two carbonic anhydrase isoforms in gills of the blue crab Callinectes sapidus SERRANO, Laetitia*; HALANYCH, Kenneth/M; HENRY, Raymond/P; Auburn University, Alabama; Auburn University, Alabama; Auburn University, Alabama serrala@auburn.edu
Hemolymph osmolality and changes in carbonic anhydrase (CA) activity and mRNA expression were measured in ion-transporting (G7) and respiratory (G3) gills in Callinectes sapidus acclimated to 35ppt and transferred to 15ppt. Expression of a putative housekeeping gene, arginine kinase (AK), was also studied. Osmolality rapidly decreased from 1100 mOsm and stabilized at 780 mOsm by 24hr. In crabs acclimated to 35ppt, AK levels were 4-fold higher in G7 than in G3. After transfer to 15ppt, mRNA expression exhibited a progressive increase in G7 from 6hr to 7d but remained relatively stable in G3. Two CA isoforms were sequenced from gills. CA1 and CA2 cDNA encode proteins showing high-scoring matches to cytoplasmic CA isoforms. CA1 and CA2 mRNA expression was low and not different in G3 and G7 in crabs at 35ppt. No changes were observed in G3 after transfer to 15ppt. CA1 mRNA expression in G7 exhibited a 4-fold and 6-fold increase at 2 and 6hr post-transfer and then decreased at 12-24hr. A second rise occurred at 48hr and declined at 28d after transfer. CA2 mRNA expression was induced 100 fold in G7 between 2 and 12hr, after which mRNA levels remained constant with one peak of expression at 48hr. CA1 was expressed at a level 500 times greater than CA2 in G7 at 35ppt and about 10 times higher 6hr and 7d at 15ppt. The initial increase in CA activity in G7 occurred at 24hr and it continued to rise through 7d. No changes in activity were observed in G3. These results indicate that low salinity-stimulated CA induction is under transcriptional regulation. The different isoforms expression patterns and their relative amount suggest that CA1 is the physiologically important isoform for ion regulation in low salinity. Supported by NSF IBN 02-30005 to RPH.
