ENDOTHELIN PROTEIN EXPRESSION IN TEAR GLANDS OF THE RABBIT

Purpose. Endothelin-1 (ET-1) has been found to accelerate rabbit corne al epithelial wound healing in vivo and proliferation of rabbit and bo vine epithelial cells in vitro. We have now determined that Endothelin -like immunoreactivity (ET-LI) is present in the tear fluid of New Zea land white rabbits, and we have addressed the question of whether it i s produced by the tear glands (lacrimal gland and Harderian gland). Me thods. Tears were obtained with capillary pipettes and lacrimal gland fluid was collected by cannulation. ET-LI was determined with a sandwi ch-enzyme immunoassay. The reverse transcriptase-polymerase chain reac tion (RT-PCR) was employed to determine if there are gene transcripts for prepro ET-1 in tear glands. ET-LI in the tear glands was evaluated using immunohistochemistry. Results. The tears contained 13.85 +/- 3. 94 pg/ml (mean +/- SEM, n = 6) ET-LI and the lacrimal gland fluid had 24.90 +/- 6.00 pg/ml (n = 6). The plasma contained 0.89 +/- 0.20 pg/ml (n = 6). Gene transcripts were identified for prepro ET-1 in the lacr imal and Harderian glands. Specific staining for ET-LI was found in th e epithelial cells of the ducts of the lacrimal gland and the acinar c ells of the Harderian gland. Conclusions. The higher concentrations of ET-LI in the tears and the lacrimal gland fluid than in plasma along with prepro ET-1 gene transcripts in the tear glands suggest that they secrete ET-1.