Effect of hemodialysis membrane type on parathyroid hormone removal.

We studied the effect of polyacrylonitrile (PAN), polysulfone (PS) and cuprophane (CP) membranes on the removal of intact and middle molecule (MM) parathyroid hormone (PTH) during hemodialysis in 4 patients using a dialysis calcium of 1.0 mmol/l. Blood was taken from the arterial (predialyzer membrane) and venous (postdialyzer membrane) limbs of the dialysis circuits at the start, midpoint and end of dialysis. Intact PTH and MM PTH levels were significantly reduced by passage through dialyzers with PAN and PS membranes; the patients' plasma ionized calcium (predialyzer membrane) fell during the course of dialysis regardless of membrane type used. This was despite a rise in plasma ionized calcium during passage through the dialyzers containing PAN and CP membranes.