Adsorption of atrial natriuretic peptide to different materials: a factor influencing results of in vitro experiments?

Studies on atrial natriuretic peptide (ANP) in ex vivo situations, include a risk of adsorption to surrounding materials. In order to investigate this potential source of error, known concentrations of ANP in Krebs solution were prepared in test tubes of different materials. The solutions were analyzed for ANP-concentration by radioimmunoassay (RIA), using a standard-curve of ANP in phosphate buffer supplemented with 0.1% human serum albumin (HSA) and 0.1% Triton X100. A considerable adsorption was seen to the different materials tested, also to siliconized glass and polypropylene. With 1 ml ANP-solution in concentrations from 1 x 10(-9) to 1 x 10(-5)M an adsorption varying between 10 and 31% was seen to a 15 cm2 polystyrene-surface, corresponding to a conventional test tube. With 1 ml of ANP 120 pM in Krebs solution serially dispensed into six empty polystyrene test tubes, 73% of the initial peptide amount was lost due to adsorption. The adsorption could be prevented or partly reversed by adding HSA or Triton X100 to the solutions. These findings indicate that adsorption entails a risk of disturbing the results of in vitro experiments in studies on ANP.