Agonist
A drug that has affinity for, and stimulates physiological activity via, cellular receptors that are normally stimulated by naturally occurring substances.
Angiotensin
A peptide that is produced by a biochemical reaction caused by the enzyme renin. Angiotensins occur in several forms: the two most important are angiotensin I, which is inactive, and angiotensin II, which is the active form.
Antagonist
A substance that tends to nullify the action of another; in pharmaceutical terms, a drug that binds to a receptor without eliciting a biological response.
Apoptosis
Programmed cell death.
Cardiovascular
Referring to the heart and circulatory system.
Congestive heart failure
A condition where there is ineffective pumping of the heart leading to accumulation of fluid in the lungs.
Contractility
The shortening of a muscle.
Dyspepsia
Abdominal symptoms located in the upper gastrointestinal tract, including hunger sensations, early satiety, indigestion, pain etc.
Enzyme
Protein substance which catalyses a biochemical reaction.
Gastrointestinal
Referring to the stomach and intestine.
Hypertrophy
Increase in the number of cells in a tissue.
IBS
Irritable bowel syndrome: abdominal symptoms relating to the lower gastrointestinal tract.
Ligand
A molecule that reacts to form a complex with another molecule.
Mucosa
A mucous membrane.
RAS
The renin-angiotensin system (RAS) or the renin-angiotensin-aldosterone system (RAAS) is a hormone system that regulates blood pressure and water (fluid) balance.
When blood volume is low, the kidneys secrete renin. Renin stimulates the production of angiotensin. Angiotensin causes blood vessels to constrict, resulting in increased blood pressure. Angiotensin also stimulates the secretion of the hormone aldosterone from the adrenal cortex. Aldosterone causes the tubules of the kidneys to increase the reabsorption of sodium and water into the blood. This increases the volume of fluid in the body, which also increases blood pressure.
If the renin-angiotensin-aldosterone system is too active, blood pressure will be too high. There are many drugs that interrupt different steps in this system to lower blood pressure. These drugs are one of the main ways to control high blood pressure (hypertension), heart failure, kidney failure, and harmful effects of diabetes.
Receptor
A specific molecule on the surface or within the cytoplasm of a cell that recognises and binds with other specific molecules, such as the cell molecules that bind with hormone or neurotransmitter molecules and react with other molecules that respond in a specific way.
Renin
An enzyme produced by the kidneys.
Retention
Holding back.