Preference threshold for NaCl solutions and sodium homeostasis in hypophysectomized rats.
The NaCl preference threshold concentrations of male hypophysectomized (hypox) and intact rats were determined using a two-bottle choice paradigm. Although hypox rats ingested more total fluid daily (ml/100 g body weight), including water and NaCl solution, than intact rats, there were no significant differences between groups in either preference threshold (8.0 mEq/l) or preference maximum (90 mEq/l) concentrations. Further, the ratio of NaCl to total fluid ingested did not differ between hypox and intact groups throughout the large range of concentrations of NaCl solution presented to them. To assess their ability to conserve sodium, both intact and hypox rats were maintained on a sodium-deficient diet and distilled water for 3 days. Both groups reduced their urinary sodium outputs significantly compared to counterparts maintained on a sodium-replete diet. This suggests that the functional integrity of the renin-angiotensin-aldosterone system was maintained in the hypox rats. Resting plasma aldosterone concentrations, measured at the end of the experiment, did not differ significantly between groups. Assessment of completeness of hypophysectomy was made by measurement of daily urinary excretion of epinephrine and by change in body weight during the course of the experiment. Daily urinary excretion of epinephrine by hypox rats was reduced to one-tenth that of intact controls. Hypox rats also failed to grow during the course of the experiment. By application of both of these criteria, the rats were completely hypophysectomized.
Department of Physiology, College of Medicine, University of Florida, Gainesville 32610.
M J
MJ
Fregly
N E
NE
Rowland
D000450:Aldosterone / Q000097:blood; D000818:Animals; D001066:Appetite / Q000502:physiology*; D001522:Behavior, Animal / Q000502:physiology; D003404:Creatinine / Q000652:urine; D004298:Dopamine / Q000652:urine; D004327:Drinking Behavior / Q000502:physiology*; D004837:Epinephrine / Q000652:urine; D007016:Hypophysectomy; D008297:Male; D009638:Norepinephrine / Q000652:urine; D051381:Rats; D011919:Rats, Inbred Strains; D012084:Renin-Angiotensin System; D012964:Sodium / Q000652:urine; D012982:Sodium, Dietary / Q000008:administration & dosage / Q000378:metabolism*; D012996:Solutions; D013649:Taste / Q000502:physiology*; D013652:Taste Threshold / Q000502:physiology*
D012982:Sodium, Dietary; D012996:Solutions; D000450:Aldosterone; D012964:Sodium; D003404:Creatinine; D004298:Dopamine; D009638:Norepinephrine; D004837:Epinephrine