Haemodynamic Effects of Apelin Agonists and Antagonists in Man in COPD With Raised Pulmonary Artery Pressures

The purpose of this study: To investigate the physiological role of apelin in the cardiovascular system in patients with COPD with raised pulmonary artery pressures. Study Aim and hypotheses: The primary objective is to test the above hypotheses using forearm blood flow and systemic infusions of apelin peptides. Hypotheses: 1. Apelin agonists are vasodilators in human resistance vessels and this effect will be altered in patients with pulmonary hypertension. 2. Apelin peptides improve right ventricular and pulmonary haemodynamics in patients with elevated pulmonary artery pressures. Study 1a - A validation dose study of 3 apelin agonists performed in healthy volunteers and COPD patients with elevated pulmonary artery pressures. Study 1b- A validation dose study of apelin receptor antagonist, in healthy volunteers and COPD patients with elevated pulmonary artery pressures. Study 2a - To define the haemodynamic response to apelin agonists in healthy volunteers and evaluate the response. Study 2b - To investigate the haemodynamic response to 3 apelin agonists in COPD patients with elevated pulmonary artery pressures.