Studies on nonmammalian nephrons

In this review the author has summarized the results of studies to date with isolated, perfused renal tubules from nonmammalian vertebrates. He tried to stress the most important findings with regard to the transport of fluid, electrophysiology and the transport of inorganic ions, and the transport of organic substances. Although most nonmammalian renal tubules appear to be no easier, and in many cases more difficult, to tease out and perfuse in vitro than mammalian renal tubules, they often offer special advantages for physiological studies. These may take the form of size (for example, the large size of amphibian cells for intracellular recordings), unusual transport properties (for example, the secretion of fluid by flounder proximal tubules or the response of the sodium transport mechanism of snake distal tubules to high concentrations of luminal sodium), or exaggerated transport properties (for example, uric acid secretion by snake proximal tubules). These same properties may also be important in terms of the renal adaptation of the animals to their environment. Clearly, much more work needs to be done on all the properties discussed here, but there are undoubtedly tubules of other species that will offer unique opportunities for phsyiological studies to the imaginative investigator.