Introduction
Glucagon is a hormone of the human body, which has the task to raise the blood sugar level. It therefore acts as an antagonist to the hormone insulin. The hormone of the pancreas, glucagon, also consists of protein (29 amino acids in total).
It is produced in the so-called A-cells of Langerhans’ islet cells in the pancreas via two precursors. First, preproglucagon is formed as a precursor. Proglucagon (glicentin) is split off from this, from which the hormone glucagon is then produced.
The glucagon receptor is also located on the cell surface. Somatostatin is composed of protein and also acts via a cell surface receptor. If corresponding stimuli occur in the body, the glucagon is released directly into the bloodstream.
These stimuli include a drop in blood sugar levels (hypoglycemia), amino acids in food or physical stress as the strongest stimulus. Hormones such as insulin and somatostatin and an increased blood sugar level (hyperglycemia) inhibit the release of glucagon. The hormone glucagon is by and large the antagonist of insulin.
Generally speaking, glucagon serves to mobilize energy reserves. The hormone increases blood sugar by stimulating the emptying of sugar stores in the liver. This process is called glycogenolysis, because the stored sugar is in the form of glycogen.
The hormone also increases the breakdown of fatty acids (lioplysis), the breakdown of protein (proteinolysis) and the formation of ketone bodies from fatty acids. Furthermore, glucagon produces sugar (glucose) from other substances in the body (gluconeogenesis). In order to get to these substances, the degradation of superordinate products is necessary.
This breakdown is called catabolism and the substrates produced include lactic acid (lactate), proteins and glycerine (from the fat metabolism). Furthermore, the hormone glucagon also has effects independent of the metabolism, including the increase of heart strength and kidney filtration for urination.