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Influence of Plasma Urea on Urine Concentration in the Opossum (Didelphis marsupialis virginiana)

Naturevolume 207pages866867 (1965) | Download Citation



INCREASING the amount of urea in the plasma has been shown to enhance urine concentration in many mammals (man, cat, dog, sheep, white rat, kangaroo rat, jerboa1,2, and rabbit3). In some mammals, however, changing the concentration of urea does not affect urine concentration; in the pig, beaver and Aplodontia, enhancement does not occur1,3. It was hypothesized that the inability of the latter group to raise its urine osmotic ceiling following increases in plasma urea is a primitive condition because these species are relatively primitive, phylogenetically.

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  1. Department of Zoology, Montana State University, Missoula, Montana

    • R. K. PLAKKE
    •  & E. W. PFEIFFER


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