Effect of extracellular fluid volume expansion on maximum glucose reabsorption rate and glomerular tubular balance in single rat nephrons

• Text
• PDF

Abstract

Extracellular fluid volume expansion with isotonic saline (7.5% of body weight) decreased maximum glucose reabsorption rate by rat kidneys at plasma glucose concentrations greater than 30 mM. Glucose reabsorption rate was 30.2 ±1.6 (SE) μmoles/min·g kidney in nonexpanded rats; it was 18.4 ±1.5 μmoles/min·g in volume-expanded rats. Glucose reabsorption determined by micropuncture was 92% complete at the end of accessible superficial proximal convolutions. Volume expansion resulted in a slight but statistically insignificant reduction of maximal glucose reabsorption rate in superficial nephrons from 786 ±35 μμmoles/min·g kidney in nonexpanded rats to 720 ±30 μμmoles/min·g in volume-expanded rats. Superficial nephron filtration rate was increased by volume expansion from 28.8 ±1.2 nl/min·g to 36.6 ±1.5 nl/min·g kidney. In nonexpanded rats, the ratio of glucose reabsorption to glomerular filtration (tmg/sgfr) was similar in superficial and juxtamedullary nephrons. In volume-expanded rats superficial nephron tmg/sgfr was greater than juxtamedullary nephron tmg/sgfr. Juxtamedullary nephron function was measured by puncturing loops of Henle in the exposed papillae of small rats.

Authors

Andrew D. Baines, John H. V. Bishop