At low infusion rates of 3-5 mcg/kg/min, what action is produced by dopamine?
(A) Vasoconstriction (B) Increased renal blood flow (C) Increased cardiac contractility (D) Decreased blood pressure
(B) Ans: B. Increased renal blood flow(Ref: Goodman Gilman 12/e p355; KDT 7/e p134. 6/e p507)Action of dopamine:At low concentrations (2 to 5 mcg/kg per minute):Primarily acts on vascular D1 receptors.Mainly renal, mesenteric & coronary beds.By activating adenylyl cyclase a raising intracellular cyclic AMP concentrations.D1 receptor stimulation a Vasodilation.Increases in glomerular filtration rate, renal blood flow & Nat+ K+ - ATPase pump.