Fasting and refeeding. III. Antinatriuretic effect of oral and intravenous carbohydrate and its relationship to potassium excretion

Abstract Volunteers maintained on a constant sodium, potassium, and fluid intake underwent a water diuresis to examine the antinatriuretic effect of glucose after fasting and to determine its relationship to the changes in circulating insulin, free fatty acids, and other substrates that accompany refeeding with carbohydrate. Further studies were performed to observe the relationship between sodium and potassium excretion as influenced by both oral and intravenous glucose in the fed and fasted state. The results indicate that the natriuresis of fasting was readily reversed by intravenous, as well as oral, glucose and that this effect is independent of changes in circulating insulin and free fatty acids. The ingestion of glucose caused a significant decrease in urinary potassium excretion in both the fed and fasted state. This reduced excretion of potassium occurred independently of glomerular filtration rate and sodium excretion but was seen only when plasma potassium declined.