Abstract
Sevelamer hydrochloride (sevelamer) is a non-absorbed calcium (Ca)-free phosphate (P)-binding polymer for the treatment of hyperphosphatemia in patients undergoing hemodialysis. The time-course changes of serum P, Ca, and parathyroid hormone (PTH) levels after normal and high P diets-containing sevelamer were investigated in normal and partially nephrectomized rats under time-scheduled feeding (9:30-11:00). The high P diet feeding transiently increased serum P and PTH levels in normal rats, while the sevelamer treatment completely inhibited these increases. The high P diet feeding enhanced the amplitude of hyperphosphatemia but an additional increase in the serum PTH level was not observed in rats with renal insufficiency. Sevelamer treatment inhibited elevations of serum P and Ca×P levels during several hours demonstrating a beneficial effect of sevelamer on metastatic calcifications in hemodialysis patients. Serum PTH levels just before feeding were increased in both the normal and renal failure rats fed high P diet. Thus, it has been suggested that even though hyperphosphatemia caused by high P diet is transient, when exposure is repeated daily, it could promote parathyroid hyperfunctioning.
