The Shift of Thermoneutral Zone in Striped Hamster Acclimated to Different Temperatures

Abstract

Temperature affects all biological functions and will therefore modulate ecologically significant interactions between animals and their environment. Here, we examined the effect of ambient temperature (Ta) on the thermal biology and energy budget in striped hamsters acclimated to cold (5°C), warm (21°C) and hot temperatures (31°C). Thermoneutral zone (TNZ) was 22.5–32.5°C, 25–32.5°C and 30–32.5°C in the cold-, warm- and hot-acclimated hamsters, respectively. The cold acclimation decreased the lower critical temperature and made the TNZ wider, and hot exposure elevated the lower critical temperature, resulting in a narrow TNZ. Within the TNZ, cold-acclimated hamsters showed a significantly higher rate of metabolism and thermogenesis than those acclimated to hot temperature. Digestive enzymes activities, including intestinal sucrase, maltase, L-alanine aminopeptidase-N and leucine aminopeptidase were higher in the cold than in the hot. The changes in metabolic rate and thermogenesis at different temperatures were in parallel with cytochrome c oxidase activity and uncoupling protein 1 gene expression of brown adipose tissue. This suggests that the shift of the lower critical temperature of TNZ is possibly associated with the rate of metabolism and thermogenesis, as well as with the digestive capacity of the gastrointestinal tract at different Ta. The upper critical temperature of TNZ may be independent of the changes in Ta. The changes of lower critical temperature of TNZ are an important strategy in adaption to variations of Ta.

Plasticity in gastrointestinal morphology and enzyme activity in lactating striped hamsters (Cricetulus barabensis)

“…The activity of several digestive enzymes was measured in whole-tissue homogenates rather than in mucosal samples to avoid underestimation of activity as previously reported (Brzek et al, 2009;Liu and Wang, 2007;Martinez, 1990;Zhao et al, 2014b). The tissue protein content was determined by the Folin phenol method with bovine serum albumin as the standard (Lowry et al, 1951).…”

“…Activity of pepsin, maltase and sucrase As described previously (Zhao et al, 2014b), we measured the activity of pepsin (EC 3.4.23.1), sucrase (EC 3.2.1.48) and maltase (EC 3.2.1.20) using commercial kits (Jiancheng Biotech Co. Ltd, Nanjing, China) according to the manufacturer's protocols. The inter-and intra-assay variations were, respectively, 5.6% and 2.5% for pepsin, 5.0% and 3.1% for sucrase and 5.1% and 3.1% for maltase.…”

“…The reaction was terminated by using a stop solution, followed by 1 ml detective reagent solution, and the absorbance was read at 505 nm. The activity of both enzymes was expressed in U min −1 (1 U was defined as 1 nmol sucrase or maltase hydrolyzed at 37°C by 1 mg tissue protein per minute; Zhao et al, 2014b).…”

“…Relative mRNA expression of several neuropeptides was quantified using real-time reverse transcription-quantitative PCR (RT-qPCR) analysis, as described previously (Zhao et al, 2014b). RNA isolation from the hypothalamus was carried out using a Trizol kit (Takara Bio, Dalian, China) according to the manufacturer's instructions.…”

“…We have previously observed that food intake increased greatly in hamsters during lactation and when exposed to cold conditions (Zhao et al, 2010;Zhao, 2011), and that leptin may be involved in the energy balance regulation (Zhao et al, 2014a,b). Significant plasticity of gut size and digestive enzymes indicative of the activities of sucrase, maltase and aminopeptidase occurs in hamsters acclimated to different temperatures (Zhao et al, 2014b). Female hamsters reach sexual maturity at 3.0-3.5 months of age, and body mass of adult females averages 25.5 g; the length of pregnancy and lactation are 19-21 days and 17-19 days, respectively; natural litter size ranges from 3 to 8, and the mean litter size is 5.2.…”