Meeting Abstract
P2.124 Monday, Jan. 5 A Comparative Study of Urea-Induced Hypometabolism in Ectothermic Animals MUIR, TJ*; COSTANZO, JP; LEE JR, RE; Miami University; Miami University; Miami University Muirtj@muohio.edu
Many organisms endure extended periods of dormancy by depressing their metabolism, effectively prolonging their endogenous energy-stores. Though the mechanisms of hypometabolism are incompletely understood, recent evidence suggests that urea accumulation in autumn and early winter reduces metabolism by 25% in hibernating wood frogs (Rana sylvatica). Moreover, metabolic rates of isolated tissues were reduced by 50% in skeletal muscle and 20% in liver when they were tested in the presence of urea. In addition to R. sylvatica, species from several taxa accumulate urea during extended dormancy and may benefit from its putative hypometabolic effect. To investigate the phylogenetic breadth of the hypometabolic response to urea, we studied four animals that accumulate urea during dormancy from the clades Amphibia (Scaphiopus bombifrons and Ambystoma tigrinum), Reptilia (Malaclemys terrapin), and Mollusca (Anguispira alternata). Rana pipiens, a close relative of R. sylvatica that does not accumulate urea during hibernation, was used to shed light on whether urea-induced metabolic depression was exclusive to urea accumulators. For each animal, we measured rates of oxygen consumption of isolated tissues in the presence or absence of physiological concentrations of urea. Tissues from some species had reduced metabolic rates in the presence of urea, whereas those from other species showed no effect. Our results suggest that the urea-induced hypometabolism initially discovered in R. sylvatica is present in at least some tissues of other animals that accumulate urea during dormancy. Lastly, urea did not affect metabolism of tissues from R. pipiens, suggesting that R. sylvatica and other urea-accumulators may have specially-adapted metabolic machinery that is particularly susceptible to perturbation by urea. Supported in part by NSF grant IAB 0416750.
