FACTORS INFLUENCING THE RESPONSE OF ISOLATED DOGFISH SKIN MELANOPHORES TO MELANOCYTE-STIMULATING HORMONE

Abstract

This report presents new information bearing on the hormonal control of melanophores in a relatively primitive vertebrate form. Skin from spiny dogfish, Squalus acanthias. was paled in Ringer''s solution, Darkening was measured reflectometrically. The log dose-response curves to standard melanocyte-stimulating hormone (MSH), to bovine [beta]-MSH and to synthetic [alpha]-MSH are presented. Hypotonic Ringer''s solution caused some darkening and MSH action was inhibited in hypertonic media. Urea was not required for the response to MSH. It was found possible to replace NA by any of a variety of cations and still obtain a response to MSH. Thus, Li, choline, K or Mg could all replace Na. However, removal of all ions from the medium in-hibited the response to MSH. These results contrast with the established absolute Na requirement for MSH action on the skin of the frog, Rana pipiens. Caffeine at 0.01[image] was also found to be an effective darkening agent.