Control of phosphate excretion in uremic man

Abstract

A B S T R A C T The present studies were performed in an effort to examine the characteristics of the control system governing phosphate excretion in uremic man. In a group of patients with glomerular filtration rates (GFR) ranging from normal to 2 ml/min, it was found that the lower the GFR the lower the fraction of filtered phosphate reabsorbed (TRP). On a fixed phosphate intake, phosphate excretion rate was the same in patients with GFRs ranging from 60 to 3 ml/min. When plasma phosphate concentrations were diminished to subnormal levels in hyperphosphatemic, hypocalcemic uremic patients, TRP values increased but did not return to normal. TRP failed to rise substantially when GFR, as well as plasma phosphate concentrations, were diminished. In patients with unilateral renal disease, TRP values were equal bilaterally, and values were substantially higher in the diseased kidneys than in patients with bilateral involvement. When plasma calcium concentrations were raised to normal for 2-3 wk in uremic patients in whom plasma phosphate concentrations had previously been lowered to subnormal levels, TRP values rose to an average value of 86%o. Values remained in the normal range when phosphate concentrations were allowed to increase while normocalcemia was maintained. The data are interpreted to indicate that in advancing renal disease, the changing patterns of phosphate excretion are mediated by a control system in which parathyroid hormone serves as a

Mineral (Mal)Adaptation to Kidney Disease—Young Investigator Award Address

“…Since individuals with normal GFR who consume typical Western diets excrete only 10%-20% of their filtered load of phosphate-the fractional excretion of phosphate-the kidney can readily respond to reduced filtration of phosphate by commensurately decreasing the percentage that NPT2a and NPT2c reabsorb. Indeed, fractional excretion of phosphate often increases from 10%-20% to $50% in CKD (9,10,13,14).…”

On the influence of extracellular fluid volume expansion and of uremia on bicarbonate reabsorption in man

“…Urine was collected using an in-lying Foley catheter. Special precautions were taken to maintain sterility (6). These included the use of an antibiotic ointment for lubricating the catheter and rinsing of the bladder with a neomycin solution at the conclusion of the study.…”

Environmental phosphate differentially affects virulence phenotypes of uropathogenicEscherichia coliisolates causative of prostatitis

“…26 Hyperphosphaturia, an excess of phosphate in urine, was described under several health disorders, such as cases of multiple myeloma, kidney diseases or excess of vitamin D in the body, among others. [27][28][29][30][31][32][33] Depending on the clinical case, Pi concentrations in urine from 20 to 50 mM were found.…”