Duct system of the rabbit lacrimal gland: structural characteristics and role in lacrimal secretion.
OBJECTIVE
To develop a nomenclature for the lacrimal duct system in the rabbit, based on the anatomic and structural characteristics of each duct segment, and to provide RT-PCR and immunofluorescence data to support the notion that the duct system plays important roles in lacrimal function.


METHODS
Paraffin-embedded lacrimal glands (LGs) were stained with hematoxylin and eosin (H&E) and evaluated with a stereomicroscope. Cryosections of LG were stained with cresyl violet, and acinar cells and ductal epithelial cells were isolated from each duct segment by laser capture microdissection (LCM). mRNA levels from these cells were analyzed by real-time RT-PCR. Standard protocol was followed for immunofluorescence detection of ionic transporters.


RESULTS
The lacrimal duct system was divided into six segments on the basis of morphologic characteristics: the intercalated, intralobular, interlobular, intralobar, interlobar, and main excretory ducts. Although the morphologic features change incrementally along the entire duct system, the gene expression of ionic transporters and aquaporins, including AE3, AQP4, AQP5, CFTR, ClC2gamma, KCC1, NHE1, NKAalpha1, NKAbeta1, NKAbeta2, NKAbeta3, and NKCC1 varied greatly among duct segments. Immunofluorescence results were generally in accordance with the abundance of mRNAs along the acinus-duct axis.


CONCLUSIONS
Most LG research has focused on the acinar cells, with relatively little attention being paid to the lacrimal ducts. The lack of knowledge regarding the lacrimal ducts was so profound that a precise nomenclature had not been established for the duct system. The present data establish a nomenclature for each segment of the lacrimal duct system and provide evidence that ducts play critical roles in lacrimal secretion.
Ding
Chuanqing
C
Department of Cell and Neurobiology, University of Southern California, Los Angeles, California 90089-9112, USA.
Parsa
Leili
L
Nandoskar
Prachi
P
Zhao
Ping
P
Wu
Kaijin
K
Wang
Yanru
Y
D000818:Animals; D020346:Aquaporins / Q000235:genetics; D004847:Epithelial Cells / Q000166:cytology; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D017136:Ion Transport / Q000235:genetics; D007765:Lacrimal Apparatus / Q000033:anatomy & histology* / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013666:Tears / Q000378:metabolism*; D009626:Terminology as Topic
D020346:Aquaporins; D012333:RNA, Messenger