ニワトリにおける肝臓と腎臓のアクアポリン（AQP）遺伝子発現に対する絶食と再給餌の影響

　Aquaporin (AQP) which is a water channel, is also including the group (aquaglyceroporin) letting glycerol or urea go through as well as a water molecule. In mammals, AQP7 and AQP9 which are aquaglyceroporin have a role in the transportation of glycerol related to the gluconeogenesis in the liver. It is reported that AQP9 increases uptake of glycerol in the liver, when blood glucose level decreases. This study investigated the effect of AQP9 and AQP7 mRNA levels in liver and kidney in relation to the fasting and the re-feeding in the chicks. The purpose of this study was to determine whether the functions of AQP9 and AQP7 in the chicks are similar to mammals. One-day old chicks were kept with free access to water and food until 7-days old. At 7-days old, chicks were divided into three groups of 6 chicks : a control groups with free access to food and water and a fasting group with free access to water but not to water for 24 hours, a re-feeding group with free access to food and water for 6 hours after fasting treatment. At the end of the experiments all the chicks were sacrificed and blood and tissues (liver and kidney) were taken for measurement of blood glucose levels and mRNA levels. Total RNA extracted and reverse transcription was performed. AQP7 and AQP9 and the phosphoenolpyruvate carboxykinase (PEPCK) mRNA levels were measured by using real-time PCR. In the fasting group, body weight significantly decreased as compared with control group, but blood glucose levels did not decrease. In the re-feeding groups, blood glucose levels significantly increased as compared with control group and fasting group. In the liver, the fasting and the re-feeding treatment did not affect AQP7 and AQP9 mRNA levels. In the kidney, the fasting did not affect AQP7 and AQP9 mRNA levels, but the re-feeding treatment significantly increased AQP7 and AQP9 mRNA levels. In the liver, PEKCK mRNA levels significantly decreased in fasting group and further decreased in the re-feeding group. The re-feeding treatment significantly increased PEPCK mRNA levels in the kidney. From these results, kidney may play a roll in the increase of blood glucose levels at the re-feeding. But, a roll in gluconeogenesis of liver is not clear in the chicks. Therefore, further study is necessary to understand the gluconeogenesis in the chicks.

研究紹介 (Research Report)