ACTH acts directly on melanocytes to stimulate melanogenesis--an in vitro study

A total of 108 whole skin organ cultures taken from vitiliginous skin were incubated in MEM containing ACTH. It was observed that 53.7% that is 58 showed a positive response with an increase in pigment production and enzyme activity, as observed on frozen sections stained for dopaoxidase activity. On immunohistochemical staining for locating ACTH binding, it is observed that 27.3% control skin and 72.7% ACTH treated skin show positivity. The ACTH is seen to bind with the melanocyte membrane as well as the cytoplasm. This indicates that ACTH can bind to the MSH-receptors expressed by the melanocyte. Thus, ACTH acts directly on the melanocyte to enhance melanogenesis and does not require to act via the adrenal-pituitary axis. This also indicates that the response is not associated with immune suppression by ACTH.