AJP - Renal Physiology, Vol 249, Issue 1 40-F48, Copyright © 1985 by American Physiological Society
Renal hydroxybutyrate and acetoacetate reabsorption and utilization in the rat
M. Barac-Nieto
Is the renal conservation of ketones effected through saturable transport
systems? Does the renal reabsorption of ketoacids limit their utilization?
The reabsorptive transport (T) and metabolic utilization (Q) of
D-3-hydroxybutyrate (HB) and acetoacetate (AA) in the kidney were measured
in anesthetized rats by use of clearance and arteriovenous extraction
determinations. THB and TAA increased in proportion with increasing HB and
AA filtered loads. Fractional THB decreases from 0.97 to 0.72 upon
increases in the plasma HB. Fractional TAA also decreases from 0.89 to
0.73, at a constant filtered AA load, when the filtered HB load increased.
Thus both saturable and nonsaturable components effect the reabsorption of
HB and AA. Renal QHB increased from 0.4 to 4 mumol X g-1 X min-1 on
increase in the plasma HB. THB always exceeded the simultaneously measured
QHB. However, QHB was significantly correlated with THB, suggesting that
QHB may be limited by delivery of HB to the renal cells through
reabsorptive pathways. There was no net renal conversion of HB and AA. Both
HB and AA were utilized by the kidney. Thus, utilized ketoacids must have
entered pathways for complete oxidation or for synthesis (lipid?) in the
kidney.
