Moreover, qPCR-analysis of the expression of G protein-coupled receptor kinases (GRKs) involved in counter-balancing sympathetic activity [4,24,25] revealed an upregulation of GRK2 and GRK5 in immunisation-induced HF, which was reverted by bothβ1EC2-CP and (to a somewhat lesser extent) by bisoprolol mono-therapy (Fig. 4C), whereas co-treatment with both substances had a clear synergistic effect, resulting even in a slight (non-significant) down-regulation of both GRK’s (Fig. 4C). Here, GRK2 is linked to hydrops fetalis.