Glucagon is a peptide hormone, produced by alpha cells of the pancreas, that raises the concentration of glucose in the bloodstream. Its effect is opposite that of insulin, which lowers the glucose concentration.The pancreas releases glucagon when the concentration of glucose in the bloodstream falls too low. Glucagon causes the liver to convert stored glycogen into glucose, which is released into the bloodstream. High blood glucose levels stimulate the release of insulin. Insulin allows glucose to be taken up and used by insulin-dependent tissues. Thus, glucagon and insulin are part of a feedback system that keeps blood glucose levels at a stable level. Glucagon belongs to a family of several other related hormones.
Function:
Glucagon is a single chain polypeptide hormone synthesized and secreted by islet α2 cells and it is a physiological antagonist of insulin. The impact on metabolism is similar to epinephrine. It has the following effects:
1. Blood glucose elevating effects: it can activate the phosphorylase in the liver, promote
hepatic glycogen decomposition and gluconeogenesis, thus increasing blood sugar
2. Positive inotropic action: it can increase intracellular cAMP levels, enhance myocardial contractility, increase cardiac output and stroke volume. Its positive inotropic effect can still manifest when applied with sufficient cardiac glycoside, and it will not be blocked by propranolol. Although it can increase heart rate and blood pressure, but will not cause arrhythmia.
3. The role on the kidney: expanding renal blood vessels, improving renal blood flow, and promoting the excretion of sodium, potassium and calcium.
4. The role on the digestive system: it can cause the smooth muscle relaxation of stomach and duodenum, small intestine and colon and inhibit stomach, small intestine and colon peristalsis, increase the secretion of bile and intestinal fluid.
5. The role on the secretion system: exciting adrenal medulla, promoting the release of catecholamines. It can also promote insulin, thyroid hormone, calcitonin and growth hormone secretion.
Application:
It is a common topical treatment for acne and can be useful against some methicillin-resistant Staphylococcus aureus (MRSA) infections. The most severe common adverse effect of clindamycin is Clostridium difficile-associated diarrhea (the most frequent cause of pseudomembranous colitis). Although this side effect occurs with almost all antibiotics, including beta-lactam antibiotics, it is classically linked to clindamycin use.
Specification: