THE AUTOCRINE DERIVATION OF THE OPIOID GROWTH-FACTOR, [MET(5)]-ENKEPHALIN, IN OCULAR SURFACE EPITHELIUM

Endogenous opioid peptides serve as growth factors in developing, rene wing, healing, and neoplastic cells and tissues. A native opioid pepti de, [Met(5)]-enkephalin, termed opioid growth factor (OGF), has been d iscovered to regulate DNA synthesis in the epithelium of the ocular su rface. OGF and its receptor 5 have been localized in both the basal an d suprabasal cells of the epithelium. This study examined the hypothes is that OGF is an autocrine growth factor. Using probe for preproenkep halin (PPE) mRNA that encodes OGF, and in situ hybridization technique s, silver grains related to PPE mRNA were detected in both basal and s uprabasal cells of the central and peripheral cornea, limbus, and conj unctiva. No distinct regional differences in the presence or location of message, as reflected by the density and distribution of PPE mRNA s ignal, were noted. These results demonstrate that a growth factor know n to serve as a tonic, inhibitory, and receptor-mediated influence on the epithelium of the ocular surface is derived in an autocrine manner , thereby permitting local control of homeostatic cellular replication . (C) 1998 Elsevier Science B.V.