Flushing and Plasma Substance P Concentration during Infusion of Synthetic Substance P in Normal Man

Abstract

Six normal subjects received synthetic substance P intravenously in successively increasing doses of 0.5, 1.0, 2.0, 4.0, and 8.0 pmol kg⁻¹ mkr⁻¹. Each dose was given for 20min. Concentrations of substance P in plasma and infusions were measured radioimmunochemically. The incremental plasma concentration of substance P correlated linearly to the dose infused. Metabolic clearance rate was 0.361 kg^_1 min⁻¹, and the half-life of exogenous substance P 1.6 min. Lacri-mation and sustained flushing were elicited at plasma concentrations above normal range. Transient flushing in spite of continued infusion was seen at 'physiological' levels. Pulse rate and blood pressure did not change significantly.

Key Words:

• Carcinoid syndrome
• flushing
• substance P