Physiology Renal physiology acccccb6 Relaxation of mesangial cells is caused by A Histamine B Dopamine C Angiotension 2 D Vasopressin High-Yield Explanation Dopamine causes relaxation of mesangial cells. Other three are agents causing contraction.Ref: Ganong&;s Review of Medical Physiology, 23rd edition, page no: 646