Abstract
Purpose:
The systemic renin-angiotensin system (RAS) plays an important role in the endocrine regulation of blood pressure and of salt and water balance. Tissue-specific RAS is present in the lacrimal gland and might be involved in tissue function of regulating tear secretion in the lacrimal gland. The purpose of this study was to investigate the effect of angiotensin II (Ang II) on tear secretion.
Methods:
Female C57BL/6 mice at an age of 8 weeks were used in this study. Mice were anesthetized by pentobarbital, and an osmotic minipump (Alzet model 2004) was implanted to deliver Ang II subcutaneously at a dose of 1.5 mg/kg/day for 4 weeks. Systolic blood pressure was measured with an automated tail-cuff device. Change in tear secretion was measured by the cotton thread test for 15 seconds. After Ang II treatment, the mice were killed by cervical dislocation. The lacrimal glands were removed for histological examination.
Results:
A significant difference was not observed in body weight gain among Ang II treatment and vehicle groups. Through the treatment period, a significant increase in systolic blood pressure we observed in Ang II treatment group (116 ± 0.55 vs 140 ± 31, P<0.001 vs vehicle, n=5, day 14). Tear secretion was lower in the Ang II treatment group than the initial value through the treatment period and significant decrease were observed compared to the vehicle group from day 3 to day14 (3.06 ± 0.88 vs 2.21 ± 0.45, P<0.001 vs vehicle, n=5, day 14). Reduction of lacrimal achiner cell area were apparent in the Ang II treatment group.
Conclusions:
These data suggest that activation of angiotensin receptor by Ang II reduces tear secretion and RAS play an important role in regulation of tear secretion.