Test of the adaptive modulation hypothesis in rodents: dietary flexibilityand enzyme plasticity

The phenotypic response of digestive enzymes was assessed in two species of rodents with different foods habits. Species were Phyllotis darwini (omniv orous) and Octodon degus (herbivorous). The activity of sucrase, maltase an d aminopeptidase-N were determined in vitro in animals feeding two contrast ing diets. No effect of dietary chemistry on sucrase and maltase activities was observed. Nevertheless, aminopeptidase-N showed a reversible response to diet in P. darwini but not in O. degus. Through Principal Component Anal ysis we separated the specific and non-specific modulation of the enzymes. The analysis showed that aminopeptidase-N activity is up-regulated by dieta ry protein in P. darwini. Differences in the phenotypic response of this sp ecies apparently reflect the historic levels of specific substrates of the natural diets for this enzyme, linking dietary flexibility and digestive pl asticity in an evolutionary context. (C) 1999 Elsevier Science Inc. All rig hts reserved.