The apelin-APJ system is a relatively new discovery. It has generated interest in part due to it's apparent ability to counteract the renin-angiotensin system, which is frequently overactive in many cardiovascular disease.

Apelin improves that pumping ability of the heart and we wish to know if this action persists in the presence of increased levels of angiotensin II.

Inclusion Criteria:

• > 18 years old
• Healthy volunteers

Exclusion Criteria:

• Lack of informed consent
• Age < 18 years,
• Current involvement in other research studies,
• Systolic blood pressure >190 mmHg or <100 mmHg
• Malignant arrhythmias
• Renal or hepatic failure
• Haemodynamically significant aortic stenosis
• Severe or significant co morbidity
• Women of childbearing potential.

Any regular medication

• Previous history of any cardiovascular disease