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Ontogeny of thermogenesis in pups of the subterranean rodent Ctenomys talarum
Congreso; 28th Congress - European Society for Comparative Physiology and Biochemistry; 2012
In mammals, during adult life and pup´s development, integrated requirements of all activities of the individual must conform to a sustained rate of metabolism. Thus, partitioning the available energy according to short-term priorities in a particular moment allow animals to survive and optimize long-term reproductive success. In altricial rodents, thermal balance might be a key factor for survival. When no exogenous source of heat is present, altricial pups rapidly lose heat reaching ambient temperature. Subterranean rodents inhabit burrows where ambient temperature remains relatively stable between narrow ranges. Pups of the subterranean rodent Ctenomys talarum are altricial, being an excellent model to evaluate the development of thermogenic capacity. In this work, we evaluate the ontogeny of thermogenic capacity of pups of the subterranean rodent C. talarum. Particularly, we evaluate the timing of UCP1 expression in brown adipose tissue (BAT), considered as source of nonshivering thermogenesis (NST). Using respirometry techniques, we estimated NSTmax, total thermogenic capacity (cold-induced maximum metabolic rate, MMR), and resting metabolic rate (RMR) in pups until day 60 (postweaning age). NSTmax (estimation that includes RMR) was similar to RMR at all ages (2-way ANCOVA, F5,62 = 1.22, P = 0.31). NSTmax showed a biphasic pattern, increasing to day 10, decreasing to day 60. MMR was similar to RMR until day 10, remaining constant after this day (F5,62 = 12.68, P < 0.001). UCP1 content in BAT was similar during pups´ ontogeny (Kruskal?Wallis, T = 5.88, P = 0.32). In brief, no NST is present in pups until day 60, becoming functional in adults. UCP1 content was similar through this period. As in surface-dwelling species, pups of C. talarum are born with small interscapular BAT deposit, but only begin to show weak NST in a postweaning stage. Interestingly, cold induced MMR is fixed at an early age, indicating an improvement in ST efficiency after day 10.