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.