Effect of age on acetylcholinesterase and other hemolymph proteins in Aplysia

Hemolymph was examined in young (ca. 86 days old), mature (ca. 163 days old), and old (ca. 294 days old) Aplysia for age-related changes in constituent proteins. In young, mature, and old animals protein concentrations were 1.6 +/- 0.27, 1.41 +/- 0.53, and 1.45 +/- 0.43 mg.ml-1, respectively. The copper-containing respiratory protein, hemocyanin, measured by determining the copper concentration, was found to increase significantly from young (0.98 +/- 0.51 microgram.ml-1) to mature (2.02 +/- 0.95 micrograms.ml-1) Aplysia, with little change between mature and old (1.92 +/- 0.43 micrograms.ml-1) animals. These findings were consistent with the results obtained when hemocyanin was directly measured by spectrophotometric absorption at 340 nm. Acetylcholinesterase (AChE) was present in the hemolymph of Aplysia. Its activity was highest in mature animals (3121 +/- 1627 units.mg-1) and least in old animals (1463 +/- 599 units.mg-1). Young animals had intermediate levels (2080 +/- 762 units.mg-1). SDS-PAGE revealed a distinct pattern of protein bands for hemolymph from each age group; hemolymph from the young group contained six prominent protein bands with molecular weights (MW) from 13 to 300 kDa. Hemolymph of mature and old animals exhibited four and three prominent protein bands, respectively, with MW between 45 and 300 kDa. A prominent band at 97 kDa was present in samples from the mature group, but was faint in samples from the old group and absent in samples from the young group.(ABSTRACT TRUNCATED AT 250 WORDS)