Lungfish Neoceratodus forsteri: Activities of Ornithine-Urea Cycle and Enzymes
Leon Goldstein 1,
Peter A. Janssens 2, and
Roy P. Forster 3
1 Department of Physiology, Harvard Medical School, Boston, Massachusetts
2 Department of Physiological Chemistry, University of Wisconsin, Madison
3 Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire
The level of activity of the ornithine-urea cycle is low in the liver of the permanently aquatic Australian lungfish. The rate of incorporation of 14C-bicarbonate into urea by liver slices was only 100th of that previously observed in the estivating African lungfish Protopterus dolloi. The activities of enzymes of the ornithine-urea cycle were similarly reduced. The low activity of this cycle in Neoceratodus is consistent with its exclusively aquatic nature.