Effect of osmolality on glucose metabolism in rabbit kidney cortex and medulla in vitro

¹ Departments of Medicine, Harvard Medical School and Peter Bent Brigham Hospital, Boston, Massachusetts

Slices of rabbit kidney cortex and medulla were incubated aerobically in media of varying osmotic concentrations. When medium osmolality was reduced below 280–300 mosmoles/kg H₂O, by means of decreased sodium chloride and sucrose concentrations, there was an osmotically determined increase in cortical glucose utilization and oxidation, lactate production, and slice weight. Between 280 and 300 mosmoles/kg H₂O maximal cortical slice weight loss and inhibition of glucose metabolism occurred, with little further change when medium osmolality was increased to 415 mosmoles/kg H₂O. With urea, slice weight and relatively maximal glucose metabolism were maintained at all medium osmotic concentrations between 67 and 548 mosmoles/kg H₂O. In contrast, slices of kidney medulla revealed a capacity for extensive glucose oxidation in hyperosmotic media (1,066 mosmoles/kg H₂O), while maximal lactate production occurred in hypoosmotic media (67 mosmoles/kg H₂O). The findings are interpreted as suggestive of responsiveness of cortical and medullary intermediary metabolism to changes in the "effective" extracellular-to-intracellular osmotic gradient.

Key Words: intermediary metabolism • aerobic glycolysis • sodium concentration • sucrose concentration • urea concentration • renal slice weight • glycogen metabolism • lactate production

Submitted on September 24, 1963