AJP - Renal Physiology, Vol 238, Issue 4 290-F295, Copyright © 1980 by American Physiological Society
Competition between sodium reabsorption and gluconeogenesis in kidneys of steroid-treated rats
P. Silva, B. Ross and K. Spokes
Kidneys of rats treated with methylprednisolone show altered substrate
requirements for sodium reabsorption when perfused in vitro. Such kidneys
synthesize glucose from lactate at twice the rate of control. Optimum
sodium reabsorption is not seen with glucose, which is normally the
preferred substrate. Sodium reabsorption is restored toward normal by the
combination of glucose and butyrate, by pyruvate, or by
3-mercaptopicolinate. All of these results point to a metabolic adaptation
in the kidney; butyrate may improve sodium reabsorption by sparing glucose,
pyruvate is a gluconeogenic precursor and an effective fuel of respiration,
and 3-mercaptopicolinate is an inhibitor of gluconeogenesis. In kidneys
from rats treated with methylprednisolone there is an increased requirement
for metabolic energy because of the increased rate of gluconeogenesis. It
is suggested that the availability of energy from glucose oxidation is
limited in part by the diversion of pyruvate back to glucose. Under these
special circumstances, gluconeogenesis competes with sodium reabsorption in
the intact kidney.
