title: Osmotic factors in restitution from thermal dehydration in rats.
abstract: The degree of voluntary dehydration after thermal dehydration was assessed while supplying drinking water of varying NaCl concentrations. Adult male albino rats were exposed to a hot-dry environment (dry bulb temp 36 degrees C; relative humidity 20%) for 6-8 h, and dehydration of 7% body wt was induced. After dehydration the rats were divided into three groups, and distilled water and 0.45 or 0.9% NaCl solution was given ad libitum. The amount of fluid intake reached an equilibrium in 6-12 h; the 0.45 and 0.9% NaCl groups regained almost all lost water, whereas the distilled water group regained only half. During rehydration the 0.45 and 0.9% NaCl groups gained Na by approximately 430-650 mueq and lost K by 90-130 mueq, whereas the distilled water group lost Na slightly and K by 80 mueq/100 g body wt. As for the electrolyte balance during thermal dehydration, rats excreted Na and K into urine and saliva. Na loss was 200 mueq/100 g, almost all of which was derived from the interstitial space of skin and skeletal muscle, and K loss was 230 mueq/100 g, almost all of which was derived from intracellular space of skeletal muscle. Total cation loss (Na, K) during thermal dehydration, including K excretion during rehydration, was 510-560 mueq/100 g, which was almost identical to the Na gained by rats given 0.45 or 0.9% NaCl solution. These results suggest that voluntary dehydration is caused by the dilutional inhibition of drinking due to loss of electrolytes during thermal dehydration.
mesh_terms: D000818:Animals; D003681:Dehydration / Q000378:metabolism* / Q000503:physiopathology; D004231:Diuresis; D004326:Drinking; D005110:Extracellular Space / Q000378:metabolism; D006358:Hot Temperature / Q000009:adverse effects*; D008297:Male; D009132:Muscles / Q000378:metabolism; D009318:Natriuresis; D009994:Osmolar Concentration; D011188:Potassium / Q000652:urine; D051381:Rats; D011919:Rats, Inbred Strains; D012867:Skin / Q000378:metabolism; D014882:Water-Electrolyte Balance
chemical_list: D011188:Potassium