ADRB3 and hydrops fetalis: Again, the nonselective β3-AR antagonist bupranalol successfully blocked the inotropic effect of purified IgGs from β3-AR Abs positive HF sera, but nadolol, a selective antagonist of β1- and β2-AR, did not, suggesting the mediation of observed IgG inotropic effects through β3-ARs rather than β1- or β2-ARs.