Meeting Abstract
15.1 Tuesday, Jan. 4 Environmental hypoxia amplifies postprandial cardiac hypertrophy in the American alligator (Alligator mississippiensis) SLAY, C.E.*; HICKS, J.W.; Univ. of California, Irvine cslay@uci.edu
The process of digestion is energetically costly, particularly for the carnivorous reptiles which naturally feed intermittently. In these animals, the metabolic response during the postprandial period, termed specific dynamic action (SDA), is characterized by a relatively large scope and duration of increased aerobic demand. The cardiopulmonary system in these animals must, therefore, systematically adjust to ensure adequate levels of gas and nutrient transport. As described in the Burmese python (Python molurus) by Anderson et al (2005), postprandial cardiac hypertrophy may be extreme (40% increase in ventricular mass), occur rapidly (within 48 hours), and serve to acutely increase cardiac output. We hypothesize that oxygen demand is the primary stimulant of postprandial cardiac hypertrophy. This study examines the consequences of limiting O2 supply during a period of peak oxygen demand. American alligators (Alligator mississippiensis) were fed large meals and exposed to hypoxia (12% O2) while digesting. Animals were euthanized 72 hours after consuming these meals, and ventricular tissue was analyzed. As compared to values of fasted animals, ventricular mass did not increase significantly in animals digesting in environmental normoxia, whereas ventricular mass increased by 17% in animals exposed to hypoxia. This suggests that while the cardiopulmonary system satisfies the aerobic demand of SDA in environmental normoxia, cardiac hypertrophy serves to increase convective oxygen transport when oxygen supply does not satisfy this aerobic demand, as during exposure to environmental hypoxia. CES would like to acknowledge support from the NSF GK-12 Fellowship (DGE-0638751 to UCI) and an NSF Graduate Research Fellowship. Additional funding was provided by NSF grant IOS 0922756 to JWH.
