MCCUE, M.D.; BENNETT, A.F.; HICKS, J.W.; University of California, Irvine: The physiology underlying specific dynamic action in pythons: a tail of two hypotheses

We have previously demonstrated that specific dynamic action (SDA) in pythons is not triggered by inert food boluses and is highly dependent on meal type. Here we further investigated physiological processes underlying SDA by testing two existing hypotheses. The first catabolic hypothesis, suggests that the majority of SDA results from the oxidative deamination of specific amino acids (i.e. alanine, glycine, and phenylalinine). This hypothesis predicts that amino acids that are deaminated via hydrolysis (i.e. arginine, asparginine, aspartic acid, and glutamic acid) would not contribute to [or contribute negatively to] postprandial elevations in metabolism [measured by oxygen consumption]. The second anabolic hypothesis suggests that the majority of SDA results from tissue growth that is fueled by a complete balance of newly assimilated amino acids. This hypothesis predicts that ingestion of incomplete amino acid mixtures (those deficient in essential amino acids) would result in reduced SDA responses compared to responses following ingestion of complete amino acid mixtures. These hypotheses were tested by feeding juvenile Burmese pythons (Python molurus) several individual amino acids (15 mmol/kg), and amino acid mixtures (30 mmol/kg). Amino acid mixtures were either complete-balanced (based on mouse composition) or deficient in specific groups of amino acids (i.e. essential, polar, etc.). Flow-through respirometry was used to quantify metabolism by measuring rates of oxygen consumption in snakes. Energy devoted to SDA during meal processing was then compared among treatments to understand how various physiological processes contribute to costs of SDA. This project was sponsored by NSF IBN-0091308 awarded to A.F. Bennett and J.W. Hicks, and NSF Graduate Research Fellowship awarded to M.D. McCue.