Rat Atrial Natriuretic Factor (ANP-III) Inhibits Phosphate Transport in Brush Border Membrane from Superficial and Juxtamedullary Cortex

Abstract
Previous studies have shown that administration of synthetic atrial natriuretic factor (ANF, 101-126) decreases sodium-dependent phosphate transport across renal brush border membrane vesicles (BBMV) in rats fed a normal or low phosphate diet. In the present study, infusion of rat ANF (atriopeptin III (ANP-III), 103-126 rat ANF) to rats fed a normal phosphate diet caused natriuretic and phosphaturic effects similar to those of ANF (101-126), but unlike ANF (101-126) did not increase the glomerular filtration rate. The effect of ANP-III infusion on sodium-dependent transport of phosphate was also determined in BBM vesicles isolated from the superficial cortex (BBMV-SC) and juxtamedullary cortex (BBMV-JM). The results indicate that ANP-III decreases phosphate transport across BBMV-SC and BBMV-JM similarly (20-24%). However, it had no effect on sodium-dependent transport of proline in these vesicles. The infusion of ANP-III to rats a normal phosphate diet inhibits phosphate uptake both in BBMV-SC and BBMV-JM and causes phosphaturia without increments in glomerular filtration rate.

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