Effects of combined Actinobacillus pleuropneumoniae challenge and change in environmental temperature on calcitonin receptor expression levels in growing pigs
We have identified through differential gene expression polymerase chain reaction that porcine calcitonin receptor expression levels could be altered in porcine leukocytes in response to Actinobacillus pleuropneumoniae (App) challenge. This study further investigates the effects of mild pleuropneumonia and changes in environmental temperature, singularly and in combination, on leukocyte expression levels of the calcitonin receptor in domestic pigs. Forty entire male pigs were allocated by weight and temperament at a starting liveweight of 33 0± 5 kg to 4 treatments: control (22°C room temperature); A. pleuropneumoniae challenge (Day 1); varied temperature (15°C for 8 h on Days 0, 1, and 2; 30°C for 24 h on Day 6); and the combined A. pleuropneumoniae challenge and varied temperature treatment. The analysis of the leukocyte expression levels of calcitonin receptor using semi-quantitative reverse transcription PCR revealed that calcitonin receptor was up-regulated in response to the A. pleuropneumoniae challenge (P < 0.001) and the temperature treatment (P < 0.001). In addition, up-regulation of the calcitonin receptor correlated with decreased weight gain, feed intake, and plasma IGF-I. Thus, expression levels of the calcitonin receptor reflect changes in growth performance associated with alteration in ambient temperature and App challenge. In addition, this study indicates that calcitonin receptor expression represents a mechanism through which endocrine and immune systems interact to affect growth.