What is the difference between lacrimal glands and lacrimal duct

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A single copy of these materials may be reprinted for noncommercial personal use only. This content does not have an English version. Both transporters are membrane channels that transport chloride across plasma membranes.

Minimal CFTR mRNA was found in acini, whereas its level was significantly higher in every duct segment, with the highest observed in the interlobar duct. Immunofluorescence results indicated that distributions of AQP and transporter immunoreactivity IR was generally in accordance with the abundance of mRNAs along the acinus-duct axis. Figure 8. Immunofluorescence of AQPs and transporters. A AQP4-IR was observed on the basolateral sides of acinar and duct cells, with duct cells arrows showing a stronger IR than acinar cells arrowheads.

D NHE1-IR was found at the basolateral membranes and within the cytoplasm of all acinar arrowhead and ductal cells, whereas the level in ductal cells was considerably higher arrows. E NKCC1-IR was also present at the basolateral membranes and within the cytoplasm of all acinar arrowheads and ductal cells arrow , but the levels were higher in the acinar cells.

F CFTR-IR green was present in punctate aggregates within the apical cytoplasm of all acinar arrows and ductal cells arrowheads , but the level in ductal cells was considerably higher. Rhodamine-conjugated phalloidin, which stains F-actin, was used to outline the morphologic profile red , also in G. NHE1-IR was found at the basolateral membranes and within the cytoplasm of all acinar and ductal cells, but the level in ductal cells was considerably higher Fig.

CFTR-IR was present in punctate aggregates within the apical cytoplasm of all acinar and ductal cells, but the level in the ductal cells was considerably higher Fig. Rhodamine-conjugated phalloidin, which stains F-actin, was used to outline the morphologic profile. The importance of the tear film and its role as an indispensable integral component of the ocular surface system is well established.

Although investigators have used various terminologies for the LG duct segments 10 — 19 e. In the present study we established a nomenclature for the lacrimal duct system in the rabbit and demonstrated the structural characteristics of each duct segment.

In general, this system was in accordance with that in the salivary gland, an exocrine gland that has received much more extensive research with respect to the features and functions of ductal segments. In the rabbit LG, we were unable to identify striated ducts comparable to those described in the salivary gland.

Striated ducts are a transitional segment between intercalated ducts and the remaining larger intralobular ducts in the salivary gland and have unique basal infoldings and numerous mitochondria, thus revealing the striations observed microscopically. This specialization greatly increases the membrane exchange area for the transport of ions and water.

In predominantly serous salivary glands parotid gland , the striated ducts are larger than in predominantly mucous glands sublingual gland , a feature associated with the role of the striated duct in modifying isotonic basic saliva to produce hypotonic saliva. The absence of striated ducts in LGs may be because the lacrimal fluid is isotonic, rather than hypotonic, as in the case of saliva, and therefore there is no need to have these ducts.

It appears that there are no distinctive morphologic features that distinguish one lacrimal duct segment from the other; rather, the cytological features change incrementally along the entire duct system. Like other exocrine secretions, it is believed that lacrimal fluid is produced in two stages: formation of a primary fluid in the secretory end pieces, or acini, and modification into the final fluid during transit through the duct system. These two stages were confirmed some time ago by micropuncture analyses of lacrimal fluids from rat and rabbit.

In an excellent study, Dartt et al. However, it was unclear from their report what duct segments were used for those studies, although it appears to have been intralobular ducts. Recent studies by Ubels et al. IOVS ;ARVO E-Abstract 22 elegantly described the presence of transport proteins consistent with potassium secretion by ductal cells of rat LG and documented that approximately genes are expressed at significantly higher levels in duct cells than in acinar cells.

Although not explicitly stated, the micrographs in Ubels' papers appear to illustrate intra- and interlobular ducts. NKA is located in the plasma membranes of all animal cells, but preponderantly in the basal-lateral plasma membranes of the epithelia that comprise barriers between the interstitial fluid and the internal environment of the epithelial cells. Depending on the asymmetric localizations of other transport proteins, NKA may power net absorption or net secretion.

The direction in which water flows across the plasma membranes is determined by osmotic gradients, which largely are established through the actions of various ion transport proteins such as just discussed. The dramatic differences of mRNA transcripts in various duct segments also suggest that each duct segment plays different roles in lacrimal function. The rabbit LG shares significant similarities with the human LG. As in humans, acinar lumens are ovoid in rabbit, whereas in mouse they are small and complexly folded with lumenal evaginations extending to the basal membrane Schechter JE, et al.

Nonetheless, the rabbit model has some unique advantages for LG studies and we believe data obtained from using these animals will help us to elucidate the mechanisms of the human LG.

In summary, the present studies established a nomenclature for the lacrimal duct system in the rabbit that was largely in accordance with that in the salivary glands, with the exception of the striated ducts. Immunofluorescence studies showed that immunoreactivity of AQPs and certain transporters was generally in accordance with the expression of various genes along the acinus-duct axis.

The data provide evidence that lacrimal ducts are actively involved in LG fluid production and modification. Further studies are warranted to characterize transport proteins and their roles in LG function. Disclosure: C. Ding , None; L. Parsa , None; P. Nandoskar , None; P. Zhao , None; K. Wu , None; Y. Wang , None. Hisada M Botelho SY.

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