M D McCue | PubMed Health

PubMed2006

Specific dynamic action: a century of investigation.

Specific dynamic action (SDA) is the term used to refer to the increased metabolic expenditure that occurs in postprandial animals. Postprandial increases in metabolism were first documented in animals over two hundred years ago, and have since been observed in every species thus far examined. Ironically, the ubiquity of this physiological response to feeding understates its complex nature. This review is designed to summarize both classical and modern hypotheses regarding the causality of SDA as well as to review important findings from the past century of scientific research into SDA. A secondary aim of this work is to emphasize the importance of carefully designed experiments and systematic hypothesis testing to make more rapid progress in understanding the physiological processes that contribute to SDA. I also identify three areas in SDA research that deserve more detailed investigation. The first area is identification of the causality of SDA in 'model' organisms. The second area is characterization of SDA responses in novel species. The third area is exploration of the ecological and potential evolutionary significance of SDA in energy budgets of animals.

Animals↗

PubMed2005

The effect of meal composition on specific dynamic action in burmese pythons (Python molurus).

We quantified the specific dynamic action (SDA) resulting from the ingestion of various meal types in Burmese pythons (Python molurus) at 30 degrees C. Each snake was fed a series of experimental meals consisting of amino acid mixtures, simple proteins, simple or complex carbohydrates, or lipids as well as meals of whole animal tissue (chicken breast, beef suet, and mouse). Rates of oxygen consumption were measured for approximately 4 d after feeding, and the increment above standard metabolic rate was determined and compared to energy content of the meals. While food type (protein, carbohydrate, and lipid) had a general influence, SDA was highly dependent on meal composition (i.e., amino acid composition and carbohydrate structure). For chicken breast and simple carbohydrates, the SDA coefficient was approximately one-third the energetic content of the meal. Lard, suet, cellulose, and starch were not digested and did not produce measurable SDA. We conclude that the cost of de novo protein synthesis is an important component of SDA after ingestion of protein meals because (1) simple proteins, such as gelatin and collagen, did not stimulate levels of SDA attained after consumption of complete protein, (2) incomplete mixtures of amino acids failed to elicit the SDA of a complete mixture, and (3) the inhibition of de novo protein synthesis with the drug cycloheximide caused a more than 70% decrease in SDA. Stomach distension and mechanical digestion of intact prey did not cause measurable SDA.

Amino Acids↗