The osmotic fragility of erythrocytes from Pekin ducks deprived of water for 24 hours

THE OSMOTIC FRAGILITY OF ERYTHROCYTES in response to water deprivation was studied in ten Pekin ducks (2.5-3.5 kg). The ducks were fed standard feed with ad lib. access to drinking water and a paddle pool. Twenty-four hours before collecting blood, they were equally allocated to a control and an experimental group. The latter (experimental) group was removed from access to water. Blood was collected by venipuncture into tubes containing EDTA to prevent coagulation. The experimental group were then provided water for two weeks before crossing over the two groups and repeating the protocol. The osmotic fragility of the erythrocytes in vitro was determined by measuring the release of haemoglobin from blood added to tubes containing serially diluted phosphate buffered saline (PBS, pH 7.4). The packed cell volume (PCV) was determined by microcentri-fugation. In 0.85% (isotonic) PBS, haemolysis of erythrocytes from the control group was 2.5% whereas for those from the water-deprived ducks it was 23%. Mean corpuscular fragility (50% haemolysis) occurred at 0.6% PBS and 0.75% PBS for the control and experimental groups, respectively. There was no difference in the PBS concentration at which complete haemolysis of erythrocytes occurred, and no difference in the PCV of the two groups. Water deprivation altered the profile of haemolysis of the duck erythrocytes in vitro, partly by increasing osmotic fragility at low dilutions of PBS. The increased haemolysis noted with isotonic PBS may indicate increased fragility independent of osmotic effects.