Osmotic fragility of desert bighorn sheep red blood cells

Abstract

1. 1. Desert bighorn sheep, Ovis canadensis cremnobates, exposed to 5 days dehydration lost 17–22% of their body weight which they were capable of replacing within 1 hr after water was made available. 2. 2. Dehydrated bighorn tolerated a 48% loss of their initial plasma volume. After less than 4 hr postrehydration, more than 50% of the lost plasma volume was replaced. 3. 3. The absorption of water from the postrehydration rumen occurred at moderate rate (1–21/hr) with 13% of the initial postrehydration fluid volume absorbed during the first hr of rehydration. Within 9 hr postrehydration, less than 50% of the imbibed rumen volume remained. 4. 4. The osmotic fragility of the desert bighorn's RBCs improved with increased dehydration. Control values for 50% lysis in hyposmotic saline decreased from 77 mM NaCl to 68 mM Nad after 5 days dehydration. 5. 5. Plasma concentration increased from 304 mOsm/1 to 345 mOsm/1 after dehydration and became regulated to control levels 4hr postrehydration. 6. 6. Red blood cell osmotic concentrations remained constant at an average of 252 mOsm/1 during dehydration, rising to 279 mOsm/11 hr postrehydration and achieved control levels 5 hr postrehydration.