Influence of haemodialysis membranes on beta 2-microglobulin kinetics: in vivo and in vitro studies.

Amyloidosis of the beta 2-microglobulin (beta 2M) type is a recently recognised complication of dialysis. We studied plasma and ultrafiltrate beta 2M in 36 chronic haemodialysis patients. Long-term dialysis with standard cuprophan membrane in non-oliguric patients and with the AN69 polyacrylonitrile membrane in oliguric patients resulted in lower plasma beta 2M concentrations (means +/- SD, 24.4 +/- 6.6 and 33.0 +/- 8.2 micrograms/ml, respectively) than with cuprophan in oliguric patients (47.0 +/- 13.2 micrograms/ml, P less than 0.01). In acute studies, plasma beta 2M (corrected for haemo-concentration) increased, although not significantly, during cuprophan dialysis (n = 10) from 40.6 +/- 12.2 to 44.8 +/- 7.6 micrograms/ml and decreased during AN69 dialysis (n = 10) from 39.4 +/- 18.0 to 24.3 +/- 7.1 micrograms/ml (P less than 0.02). After 15 min ultrafiltration, beta 2M sieving coefficient in vivo was 0.33 for AN69 but near zero for cuprophan. Total mass transfer of beta 2M across the AN69 membrane during a 4-h dialysis was 142 +/- 45.8 mg (n = 7). AN69, but not cuprophan, membrane fragments incubated in vitro with normal or uraemic plasma exhibited avid [125-I] beta 2M binding (respectively 12.9% vs 0.47% and 6.09% vs 0.06% of total beta 2M bound at 30 min, n = 6, P less than 0.001 for both). No in vitro generation of beta 2M from whole normal or uraemic blood could be demonstrated during incubation with either membrane.(ABSTRACT TRUNCATED AT 250 WORDS)