Chuyển hóa nitơ bài tiết ở kỳ nhông Trung Quốc Cynops orientalis trong môi trường nước, trên cạn, hoặc trong nồng độ amoniac môi trường cao

Springer Science and Business Media LLC - Tập 174 - Trang 113-120 - 2003
L. Weng1, W. P. Wong1, S. F. Chew2, Y. K. Ip1
1Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
2Natural Sciences, National Institute of Education, Nanyang Technological University, Singapore , Republic of Singapore

Tóm tắt

Kỳ nhông lửa bụng Trung Quốc Cynops orientalis chuyển sang lối sống thủy sinh khi trưởng thành về giới tính. Mặc dù sống dưới nước, C. orientalis trưởng thành về giới tính vẫn duy trì khả năng tổng hợp urê ở gan cao. Tuy nhiên, tỷ lệ sản xuất urê của nó thấp hơn những loài lưỡng cư trên cạn khác vì amoni nội sinh có thể khuếch tán ra môi trường bên ngoài dưới dạng NH3. Điều này giúp tiết kiệm năng lượng tế bào vì tổng hợp urê tốn nhiều năng lượng. Đồng thời, C. orientalis cũng giảm tỷ lệ bài tiết urê và bài tiết 33% tổng lượng chất thải nitrogen dưới dạng amoniac. Khi tiếp xúc với đất, C. orientalis đã tăng tỷ lệ tổng hợp urê từ việc tích lũy amoni nội sinh. Tỷ lệ tổng hợp urê tăng này nằm trong khả năng vốn có của chu trình ornithine-urea ở gan; không có sự kích thích hoạt động của carbamoyl phosphate synthetase ở gan hay ornithine transcarbamoylase và không có sự giảm sản xuất amoniac. Khi tiếp xúc với nước chứa 75 mmol.l−1 NH4Cl, tỷ lệ tổng hợp urê và bài tiết urê đều tăng. Dưới các điều kiện thí nghiệm như vậy, chu trình ornithine-urea có thể hoạt động gần đúng giới hạn của nó; glutamine bắt đầu tích lũy trong cơ thể, và sản xuất amoniac nội sinh thông qua sự phân hủy axit amin giảm.

Từ khóa

#Cynops orientalis #tổng hợp urê #amoniac #lưỡng cư #chuyển hóa nitrogen

Tài liệu tham khảo

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