Studies on the urea cycle of Biomphalaria glabrata during normal feeding activity, in starvation and with infection of schistosoma mansoni

Abstract

1. 1. Ornithine carbamyltransferase (OCT, argininosuccinate lyase (ASL and arginase activity could be determined in hepatopancreas homogenates of Biomphalaria glabrata. The activities of the OCT of 99.8 ± 34.8 μmole/g hepatopancreas/hr and ASL of 0.45 ± 0.29 μmole/g hepatopancreas/hr are in accord with the values round in other molluscs; the arginase activity of 31.6 ± 31 μmole/g hepatopancreas/hr is ver low for a pulmonate. 2. 2. Carbamylphosphate and argininosuccinate synthetase activity could not be demonstrated in the hepatopancreas of Biomphalaria glabrata with photometric methods. The presence of a “carbamylphosphate phosphatase” and an “adenosine deaminase” intefered with the method of assay employed. 3. 3. The incorporation of 14C from NaH 14CO 3 in urea by intact hepatopancreas tissue in vitro is highly suggestive that a complete urea cycle exists in Biomphalaria glabrata. 4. 4. An ureolytic activity in Biomphalaria glabrata could be determined neither with hepatopancreas homogenates nor with intact tissue of hepatopancreas in vitro. 5. 5. Under the physiological conditions “5 days starvation”, “infected with Schistosoma mansoni” and “dry keeping at a humidity of 96%”, there is a significant increase in the activities of the studied urea cycle enzymes. Corresponding increased incorporation rates of 14CO 2 from bicarbonate in urea by hepatopancreas in vitro could be measured in the above-mentioned conditions. 6. 6. The importance of the urea cycle for the NH 3 detoxification of Biomphalaria glabrata is discussed.