371: Airway ionocytes’ function is bicarbonate transport, whereas secretory cells’ is in fluid secretion

In the salivary reflex, not only secretory cells are activated, but also myo-epithelial cells are contracted to support these cells and promote the flow of saliva, and blood vessels dilate to meet the increased demands of the tissues. The various effector cells often receive nerves from both parts of the autonomic system, and interactions may occur when the nerves act on the same type of effector, or on different types of effectors. While in an experiment electrical stimulation of the sympathetic trunk may decrease a parasympathetic salivary flow by causing marked vasoconstriction, this does not occur in the salivary reflex, since the vasoconstrictors do not take part. On the contrary, the normal sympathetic vasoconstrictor tone of the resting gland is easily overcome by activity in parasympathetic vasodilator nerves when secretion starts. Pronounced synergism can be demonstrated between sympathetic and parasympathetic secretory nerves. In dogs, for instance, in which sympathetic secretion is β-adrenoceptor-mediated, this is marked in the case of fluid secretion. In rats and rabbits, in which β-receptors elicit secretion of amylase, the potentiating interaction among the nerves is striking when amylase secretion is considered. Even the random release of acetylcholine from the post-ganglionic parasympathetic axons, by itself insufficient to evoke secretion, can increase the sympathetic effects. Motor nerves interact with secretory nerves by causing myo-epithelial contraction, mechanically promoting secretion. Interactions between the nerves in their long-term regulatory function on the sensitivity of the acinar secretory and myo-epithelial cells can also be demonstrated.

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Spatial aspects of Ca2+ signalling in pancreatic acinar cells

Journal of Experimental Biology ◽

10.1242/jeb.184.1.129 ◽

1993 ◽

Vol 184 (1) ◽

pp. 129-144

Author(s):

P. Thorn

Keyword(s):

Digestive Enzymes ◽

Acinar Cells ◽

Fluid Secretion ◽

Cell Types ◽

Cellular Mechanism ◽

Pancreatic Acinar Cells ◽

Secretory Cells ◽

High Affinity ◽

High Concentrations ◽

Cell Changes

Secretory cells do not only respond to an agonist with a simple rise in [Ca2+]i. It is now clear that complex patterns of [Ca2+]i elevation in terms of space and time are observed in many cell types and that these patterns may be a cellular mechanism for the regulation of different responses. Ca2+ signalling in exocrine cells of the pancreas promotes the secretion of digestive enzymes and fluid. It has been shown that at high concentrations of agonist (acetylcholine or cholecystokinin) the [Ca2+]i response is initiated in the secretory pole of the cell before spreading across the whole cell. This site of initiation of the [Ca2+]i elevation is in the region where exocytotic release of enzymes occurs and is also the site of a Ca(2+)-dependent chloride channel thought to be crucially important for fluid secretion. Lower concentrations of agonist elicit [Ca2+]i oscillations with complex repetitive patterns characteristic of each agonist. At physiological agonist concentrations, we have recently described repetitive short-lasting Ca2+ spikes that are spatially restricted to the secretory pole of the cell. In addition to these spikes, cholecystokinin also promotes slow transient Ca2+ rises that result in a global rise in Ca2+. The inositol trisphosphate (InsP3) receptor plays a crucial role in all of these various agonist responses, most of which can be reproduced by the infusion of InsP3 into the cell. The high InsP3-sensitivity of the secretory pole is postulated to be due to a localization of high-affinity InsP3 receptors. We speculate that in response to cholecystokinin the short-lasting spikes elicit exocytosis from a small ‘available pool’ of vesicles and that the broader oscillations induce both exocytosis and cell changes that involve movement of vesicles into this ‘available pool’.

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Ca2+ signaling and fluid secretion by secretory cells of the airway epithelium

Cell Calcium ◽

10.1016/j.ceca.2014.02.001 ◽

2014 ◽

Vol 55 (6) ◽

pp. 325-336 ◽

Cited By ~ 35

Author(s):

Robert J. Lee ◽

J. Kevin Foskett

Keyword(s):

Airway Epithelium ◽

Fluid Secretion ◽

Secretory Cells

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Model of ionic transport for bovine ciliary epithelium: effects of acetazolamide and HCO 3 −

AJP Cell Physiology ◽

10.1152/ajpcell.2001.280.6.c1521 ◽

2001 ◽

Vol 280 (6) ◽

pp. C1521-C1530 ◽

Cited By ~ 22

Author(s):

Chi-Ho To ◽

Chi-Wai Do ◽

Aldo C. Zamudio ◽

Oscar A. Candia

Keyword(s):

Ciliary Body ◽

Short Circuit ◽

Ionic Transport ◽

Short Circuit Current ◽

Fluid Secretion ◽

Bicarbonate Transport ◽

Ciliary Epithelium ◽

Bathing Solution ◽

Net Flux ◽

Vectorial Model

The possible existence of transepithelial bicarbonate transport across the isolated bovine ciliary body was investigated by employing a chamber that allows for the measurement of unidirectional, radiolabeled fluxes of CO2 + HCO[Formula: see text]. No net flux of HCO[Formula: see text] was detected. However, acetazolamide (0.1 mM) reduced the simultaneously measured short-circuit current ( I sc). In other experiments in which36Cl− was used, a net Cl− flux of 1.12 μeq · h−1 · cm−2 (30 μA/cm2) in the blood-to-aqueous direction was detected. Acetazolamide, as well as removal of HCO[Formula: see text] from the aqueous bathing solution, inhibited the net Cl− flux and I sc. Because such removal should increase HCO[Formula: see text] diffusion toward the aqueous compartment and increase the I sc, this paradoxical effect could result from cell acidification and partial closure of Cl−channels. The acetazolamide effect on Cl− fluxes can be explained by a reduction of cellular H+ and HCO[Formula: see text] (generated from metabolic CO2production), which exchange with Na+ and Cl−via Na+/H+ and Cl−/HCO[Formula: see text] exchangers, contributing to the net Cl− transport. The fact that the net Cl−flux is about three times larger than the I sc is explained with a vectorial model in which there is a secretion of Na+ and K+ into the aqueous humor that partially subtracts from the net Cl− flux. These transport characteristics of the bovine ciliary epithelium suggest how acetazolamide reduces intraocular pressure in the absence of HCO[Formula: see text] transport as a driving force for fluid secretion.

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Bicarbonate transport in sheep parotid secretory cells.

The Journal of Physiology ◽

10.1113/jphysiol.1996.sp021535 ◽

1996 ◽

Vol 494 (3) ◽

pp. 819-830 ◽

Cited By ~ 19

Author(s):

M C Steward ◽

P Poronnik ◽

D I Cook

Keyword(s):

Bicarbonate Transport ◽

Secretory Cells ◽

Sheep Parotid

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Role of gap junctions in fluid secretion of lacrimal glands

AJP Cell Physiology ◽

10.1152/ajpcell.00004.2001 ◽

2002 ◽

Vol 282 (3) ◽

pp. C501-C507 ◽

Cited By ~ 44

Author(s):

Benjamin Walcott ◽

Leon C. Moore ◽

Aija Birzgalis ◽

Nidia Claros ◽

Virginijus Valiunas ◽

...

Keyword(s):

Gap Junctions ◽

Fluid Secretion ◽

Secretory Cells ◽

Cell Coupling ◽

Lacrimal Glands ◽

Liver And Pancreas ◽

Fluid Production ◽

Deficient Mice ◽

Different Doses

In glands such as the liver and pancreas, gap junctions containing connexin 26 and 32 (Cx26 and Cx32, respectively) couple the secretory cells. Uncoupling these junctions compromises the secretory function of these glands. Lacrimal glands also contain extensive arrays of gap junctions consisting of Cx26 and Cx32. We wanted to determine the role of these junctions in fluid secretion. In Cx32-deficient mice, immunocytochemistry showed that, in the male lacrimal gland, the remaining Cx26 was found evenly distributed in the membrane whereas there was little in the membranes of female glands. Western blot analysis of Cx26 showed that female Cx32-deficient mice expressed Cx26. Patch-clamp analyses of acinar cell coupling showed that the cell pairs from male glands were coupled whereas those from female glands were not. Stimulated fluid production by the glands from Cx32-deficient mice was abnormally low in female glands compared with controls at low topical doses of carbachol. The protein secretory response to different doses of carbachol was the same in all animals. These data suggest that gap junctions are essential for optimal fluid secretion in lacrimal glands.

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Ca2+-activated Cl− channel currents in mammary secretory cells from lactating mouse

AJP Cell Physiology ◽

10.1152/ajpcell.00050.2016 ◽

2016 ◽

Vol 311 (5) ◽

pp. C808-C819 ◽

Cited By ~ 6

Author(s):

Akihiro Kamikawa ◽

Osamu Ichii ◽

Junpei Sakazaki ◽

Toru Ishikawa

Keyword(s):

Apical Membrane ◽

Fluid Secretion ◽

Functional Expression ◽

Secretory Cells ◽

Channel Blockers ◽

Whole Cell Patch Clamp ◽

Slow Kinetics ◽

Steady State Current ◽

Voltage Dependent ◽

Quality Of Milk

The Cl− secretion via Ca2+-activated Cl− channel (CaCC) is critical for fluid secretion in exocrine glands like the salivary gland. Also in the mammary gland, it has been hypothesized that CaCC plays an important role in the secretion of Cl− and aqueous phase of milk. However, there has been no evidence for the functional expression of CaCC in native mammary secretory (MS) cells of lactating animals. We therefore assessed membrane current in MS cells that were freshly isolated from lactating mice using whole cell patch-clamp techniques. In MS cells, we detected CaCC current that exhibited the following characteristics: 1) Ca2+-dependent activation at the concentrations of submicromolar range; 2) voltage-dependent activation; 3) slow kinetics for activation and deactivation; 4) outward rectification of the steady-state current; 5) anion permeability in the sequence of I− > NO3− > Br− > Cl− >> glutamate; 6) inhibition by Cl− channel blockers (niflumic acid, DIDS, and CaCCinh-A01). These characteristics of native CaCC current were similar to reported characteristics of heterologously expressed TMEM16A. RT-PCR analyses showed the expression of multiple CaCC channels including TMEM16A, Best1, and Best3 in the mammary glands of lactating mice. Immunohistochemical staining revealed the localization of TMEM16A protein at the apical membrane of the MS cells. Collectively, our data strongly suggest that MS cells functionally express CaCC, which is at least partly constituted by TMEM16A. The CaCC such as TMEM16A at the apical membrane of the MS cells may influence the quantity and/or quality of milk.

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The ultrastructure of acinar cells in the external orbital gland of young and old male rats

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100082248 ◽

1978 ◽

Vol 36 (2) ◽

pp. 276-277

Author(s):

R. Carriere

Keyword(s):

Young Adulthood ◽

Acinar Cells ◽

Cell Number ◽

Male Rats ◽

Polyploid Cell ◽

Secretory Cells ◽

Age Changes ◽

Albino Rat ◽

Golgi Membranes ◽

Diploid Cells

The external orbital gland of the albino rat exhibits both sexual dimorphism and histological age changes. In males, many cells attain a remarkable degree of polyploidy and an increase of polyploid cell number constitutes the major age change until young adulthood. The acini of young adults have a small lumen and are composed of tall serous cells. Subsequently, many acini acquire a larger lumen with an irregular outline while numerous vacuoles accumulate throughout the secretory cells. At the same time, vesicular acini with a large lumen surrounded by pale-staining low cuboidal diploid cells begin to appear and their number increases throughout old age. The fine structure of external orbital glands from both sexes has been explored and in considering acinar cells from males, emphasis was given to the form of the Golgi membranes and to nuclear infoldings of cytoplasmic constituents.

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New Ultrastructural Observations on Injury and Regeneration of Cilia in Mammalian Conducting Airway Epithelium

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100099544 ◽

1981 ◽

Vol 39 ◽

pp. 624-625

Author(s):

J.L. Carson ◽

A.M. Collier

Keyword(s):

Respiratory Tract ◽

Airway Epithelium ◽

Defense Mechanisms ◽

Normal Growth ◽

Fetal Lung ◽

Secretory Cells ◽

Airway Epithelial ◽

Ciliated Cells ◽

Conducting Airway ◽

Conducting Airways

The ciliated cells lining the conducting airways of mammals are integral to the defense mechanisms of the respiratory tract, functioning in coordination with secretory cells in the removal of inhaled and cellular debris. The effects of various infectious and toxic agents on the structure and function of airway epithelial cell cilia have been studied in our laboratory, both of which have been shown to affect ciliary ultrastructure.These observations have led to questions about ciliary regeneration as well as the possible induction of ciliogenesis in response to cellular injury. Classical models of ciliogenesis in the conducting airway epithelium of the mammalian respiratory tract have been based primarily on observations of the developing fetal lung. These observations provide a plausible explanation for the embryological generation of ciliary beds lining the conducting airways but do little to account for subsequent differentiation of ciliated cells and ciliogenesis during normal growth and development.

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Analysis of the Anterior Secretory Cells of Onchidohs Muricata (Nudibranchia)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100099490 ◽

1981 ◽

Vol 39 ◽

pp. 614-615

Author(s):

Roy Skidmore

Keyword(s):

Endoplasmic Reticulum ◽

Secretory Granules ◽

Golgi Body ◽

The Body ◽

Secretory Cells ◽

Secretory Vesicles ◽

High Magnification ◽

Large Numbers ◽

Membrane Bound ◽

Sole Of The Foot

The long-necked secretory cells in Onchidoris muricata are distributed in the anterior sole of the foot. These cells are interspersed among ciliated columnar and conical cells as well as short-necked secretory gland cells. The long-necked cells contribute a significant amount of mucoid materials to the slime on which the nudibranch travels. The body of these cells is found in the subepidermal tissues. A long process extends across the basal lamina and in between cells of the epidermis to the surface of the foot. The secretory granules travel along the process and their contents are expelled by exocytosis at the foot surface.The contents of the cell body include the nucleus, some endoplasmic reticulum, and an extensive Golgi body with large numbers of secretory vesicles (Fig. 1). The secretory vesicles are membrane bound and contain a fibrillar matrix. At high magnification the similarity of the contents in the Golgi saccules and the secretory vesicles becomes apparent (Fig. 2).

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