AJP - Renal Physiology, Vol 247, Issue 4 582-F587, Copyright © 1984 by American Physiological Society
Stimulation of phosphate transport in the proximal tubule by metabolic substrates
S. R. Gullans, P. C. Brazy, L. J. Mandel and V. W. Dennis
Studies of phosphate transport in the proximal tubule have recently focused
on interactions with cellular metabolism. The present studies demonstrate
that two fatty acids, valerate and butyrate, and two tricarboxylic acid
cycle intermediates, succinate and malate, stimulate net phosphate
transport in the rabbit proximal tubule by 34-117%. Valerate had no effect
on the total uptake of inorganic [32P]phosphate into suspensions of
proximal tubules but did enhance the initial rate of influx. Net fluid
transport was unaffected by these substrates although glucose absorption
increased by 10-15% following the addition of either valerate or succinate.
Since valerate, butyrate, and succinate are known to stimulate
gluconeogenesis and respiration, we evaluated the role of gluconeogenesis
in the stimulation of phosphate transport. The addition of
3-mercaptopicolinate (1 mM), an inhibitor of gluconeogenesis, did not alter
phosphate transport, nor did it prevent the valerate-induced stimulation of
phosphate transport. We conclude that valerate, butyrate, succinate, and
malate enhance phosphate transport by the proximal convoluted tubule. This
action appears to be unrelated to effects on gluconeogenesis and may be
related to close links between phosphate transport and oxidative
metabolism.
