Effects of Uremic Plasma on α- and β-Adrenoceptor Subtypes

Abstract

Responsiveness of adrenergic receptors is decreased in patients on maintenance hemodialysis. In this study we investigated whether uremic plasma might affect adrenergic receptors. For this purpose we determined the effects of uremic plasma obtained from 10 patients on hemodialysis treatment (mean age 61 ± 3 years, dialysis frequency 3 × 4 h/week, duration of treatment 3 ± 1 years) before and at the end of the 4-hour dialysis treatment on binding of radioligands to β₁- and β₂- as well as α₁- and α₂-adrenoceptors. Plasma from 6 healthy volunteers served as control; the plasmas were studied in three dilutions: undiluted, 1:1 (v/v) and 1:4 (v/v) with saline diluted. Plasma from healthy control did not significantly affect the number of β₁- and β₂- or α₁- and α₂-adrenoceptors. On the other hand, uremic plasma significantly decreased the number of β₁- and β₂-adrenoceptors; this inhibitory effect was also observed when plasma obtained at the end of the 4-hour dialysis treatment was investigated. On the other hand, uremic plasma did not significantly decrease the number of α₁- and α₂-adrenoceptors. We conclude that in patients on maintenance hemodialysis, the presence of inhibitory substance(s) in uremic plasma could be – at least partly – responsible for the β-adrenoceptor hyporesponsiveness; the mechanism leading ot α-adrenoceptor hyporesponsiveness, however, remains to be elucidated.