Summary
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1.
Urea biosynthesis was studied in aestivating prosobranch and pulmonate snails by measuring rates of urea accumulation, incorporation rates of 14C-bicarbonate into urea and enzyme activities of ornithine cycle enzymes. Prosobranch snails (Marisa, Pila, Pomacea and Sinotaia) make little, if any urea, while in the pulmonates the ornithine cycle seems to be functioning.
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2.
Even though the ornithine cycle is functioning in Euglandina and in the helicid snails, Helix and Otala, urea did not accumulate during aestivation as it did in Heliosoma, Mesodon and Rumina. The biological significance of these differences in pulmonate urea metabolism are not yet known. However, in addition to its importance in ammonia detoxification, urea may play a role in water retention during aestivation.
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3.
Differences in enzyme activities and rates of 14C-bicarbonate incorporation into urea in Mesodon and Rumina during normal activity and aestivation indicate that urea is biosynthesized during both physiological states.
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Supported by NSF Grant GB 8738.
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Horne, F.R., Barnes, G. Reevaluation of urea biosynthesis in prosobranch and pulmonate snails. Z. vergl. Physiolgie 69, 452–457 (1970). https://doi.org/10.1007/BF00333770
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DOI: https://doi.org/10.1007/BF00333770