Feeding induces morphological remodeling but not metabolic activation in Boa constrictor (Serpentes, Boidae)

Feeding promotes increases in the mass, as well as in the secretory and absorptive capacities of the gastrointestinal organs, in addition to elevating the aerobic metabolic rate of several ectothermic vertebrates. However, the regulatory mechanisms underlying these morphological and metabolic changes remain unclear. It has been proposed that the transition from fasting to the postprandial state is accompanied by upregulation of biochemical pathways to meet the energy demands of nutrient absorption. The objective of this study was to evaluate whether feeding affects the activity of enzymes involved in the oxidative and glycolytic pathways, as well as mitochondrial volume density, in Boa constrictor. Fasting and postprandial boas (n = 23) were used to assess the maximum activities of citrate synthase (CS), pyruvate kinase (PK), and lactate dehydrogenase (LDH) in samples from the stomach, proximal intestine, and liver. Mitochondrial quantity and morphology were assessed and described using transmission electron microscopy. Overall, no significant changes were observed in enzyme activities, except for a decrease in intestinal CS activity 48 h after feeding. Mitochondrial volume density did not differ among groups, and no correlation was found between CS activity and mitochondrial abundance. The morphological remodeling of mitochondria within tissues may be associated with the observed patterns of enzymatic activity. The combined analysis of bioenergetics and mitochondrial morphology provides new insights into the regulatory mechanisms underlying postprandial metabolic responses in Boa constrictor.