Figure 5. β₂-AR signalling pathway of lipolysis in adipocytes.

In control fetuses and lambs, stimulation of the β₂-AR increases cAMP production to activate PKA to phosphorylate HSL and perilipin, which hydrolyses intracellular triglyceride stored in the lipid droplet. IUGR fetuses and lambs have lower β₂-AR concentrations, which desensitizes them to catecholamine stimulate lipolysis, resulting in less NEFA and glycerol released from adipocytes. In the diagram, reductions in the IUGR animals are portrayed by smaller font and receptor size.