Insulin is a polypeptide hormone with molecular weight of 6,000 Daltons, composed of two peptides chains, A and B, jointed by two cross-linked disulphide bonds and synthesised by the beta cells of the islets of Langherans of the pancreas. Insulin influences most of the metabolic functions of the body. Its best known action is to lower the blood glucose concentration by increasing the rate at which glucose is converted to glycogen in the liver and muscles and to fat in adipose tissue, by stimulating the rate of glucose metabolism and by depressing gluconeogenesis. Focus on hemolysis: Hemolysis interferes with the assay by degrading insulin. To prevent hemolysis consequences, SPI-BIO has an inhibitor cocktail and a procedure available.
Prolactin (PRL) is a pituitary hormone whose molecular weight is approximately 23000 Daltons. It is a single polypeptide chain composed of about 200 amino acid residues with three disulphide bonds. In mammals prolactin has been claimed to exert a wide range of different physiological effects. These include stimulation of mammary gland development and lactation, hair maturation, synergism with androgen in male sex accessory growth and maintenance and secretion of corpus luteum. PRL is predominantly under inhibitory control by the hypothalamus. Stimulation of prolactin release can be mediated by dopamine and thyrotrophin-releasing hormone (TRH).
Ghrelin discovered in 1999, is fast becoming an endocrinology target of the millennium. Ghrelin, identified in rat stomach as an endogenous ligand for the GH secretagogue receptor, is mainly produced in stomach, but has been demonstrated in many other organs. In addition to GH-releasing properties and its orexant action, ghrelin could act as an hormone having effects on gastric motility (similarity with the peptide hormone motilin), acidic secretion, cardiovascular action, antiproliferative effects, pancreatic and glucose metabolism function, sleep... Ghrelin generaises to mRNA prepro-ghrelin of 117 amino acids. This precursor is processed into ghrelin, 28 amino acids (human). Before being secreted, this peptide is octanoylated at Ser 3.