Purification, characterization, and localization of neuropeptides in the cornea

The immunologically detected neuropeptides methionine enkephalin (ME), substance P (SP), beta-endorphin (beta-End), and alpha-melanocyte stimulating hormone (alpha-MSH) were purified from bovine corneal extracts by gradient, followed by isocratic, reversed phase-high performance liquid chromatography (RP-HPLC) and characterized, after both chromatographic steps, by radioimmunoassay (RIA). Immunologically detected ME and SP were purified from canine corneal extracts by gradient RP-HPLC and characterized by RIA. An anatomical study of the bovine cornea separated the cornea into an epithelium-enriched and a stroma-enriched portion. After gradient RP-HPLC, RIA demonstrated that all the ME-like immunoreactivity was located in the corneal epithelium, whereas the SP-like immunoreactivity was distributed between the stroma and epithelium in an approximate two-to-one ratio.