Effects of 4-pentenoic acid on renal phosphate and calcium excretion in the dog

The effects of 4-pentenoic acid (4-PA) on renal excretion of phosphate and calcium were studied in anesthetized mongrel dogs. The major metabolic action of 4-PA is inhibition of long-chain fatty acid oxidation. In intact dogs undergoing modest saline diuresis, 4-PA caused significant decrease in the percentage of filtered phosphate reabsorbed. No statistically significant calciuria was observed. Similar results were observed in intact dogs undergoing more brisk saline diuresis as well as in acutely and chronically thyroparathyroidectomized dogs. However, when results were pooled, both phosphate and calcium excretions were significantly increased. The results are interpreted as demonstrating the importance of fatty acid oxidation in providing energy for the work of tubular phosphate reabsorption. Either the energy source for calcium reabsorption differs from fatty acid oxodation, or calcium reabsorption is less sensitive to changes in energy sources. The action of 4-PA is independent of the forces involved in saline diuresis and of parathyroid hormone.