The Control of Lacrimal Gland Secretion

Benjamin Walcott
Benjamin Walcott
Professor
Ph.D. Univ. Oregon

Steven Goldfine - Research Associate
Nidia Claros - Research Technician
Lana Ovcharenko - Research Technician
Chris Picken - Graduate Student
The lacrimal glands secrete a complex fluid that is essential for the maintenance of the ocular surface. These glands synthesize and secrete tear specific proteins, and transport water and immunoglobulins across the secretory epithelium to form this complex fluid. We are interested in the mechanisms of water transport across the epithelium and in its control. Understanding these processes is essential in determining the factors that reduce the water transport in dry eye disease conditions such as Sjögren’s Syndrome. The movement of water across the glandular epithelium is by osmosis due to the movement of chloride and potassium ions out of the apical membrane of the cell and into the lumen of the acinus. We are focusing, therefore, on the channels that allow the ions to move and their control. We study a mouse model of that dry eye disease (the NZB/NZW F1 female mouse) and compare them to a normal strain. We have found that there is an apparent reduction in the activity and expression level of a large potassium channel (the Maxi-K) with the development of the disease in the NZB animals. In collaboration with Dr. Brink we are using patch clamp analysis to examine channel activity in cells isolated from normal and diseased animals. We have also made antibodies to the Maxi-K channel and have used immunocytochemistry and western blotting to examine the expression and location of these channels in the tissue from animals at different stages of the disease process. The Maxi-K channel has been cloned (mslo) and therefore we are able to use northern blotting and RNAase protection assays to see if there are changes in the levels of mRNA for that channel protein that correlate with the progression of the disease. The mouse lacrimal glands are densely innervated and the secretory cells have a diverse array of neurotransmitter receptors on their surface. These receptors are coupled to a number of different second messenger systems in the cell that we believe control different aspects of the secretory function of these cells. We are using patch clamp analysis to examine the effects of different neurotransmitters on the ionic currents and looking at the interactions between these neurotransmitters that control cell secretion. In collaboration with Dr. Matthews, we are looking at the intracellular levels of Ca++ ions that have a role in regulating ion channel conductance. With Dr. Moore (Department of Physiology and Biophysics), we are also directly examining the ability of glands in the animals and in isolation to secrete fluid. The duct can be pulled into a restriction pipette and we can measure flow rate at rest and on stimulation. In addition, we can measure the ion concentrations in the secreted fluid to see if there are changes in the movements of specific ions.

Relevant Publications:

1) Walcott, B.,R.H. Cameron, E. Grine, E. Roemer, M. Pastor and P.R. Brink 1994 Anti-muscarinic acetylcholine receptor-like immunoreactivity in lacrimal glands .in: The Lacrimal Gland, Tear Film and Dry Eye Syndromes: Basic Science and Clinical Relevance. Ed. D.A. Sullivan et al Plenum Press, New York pp 61-65

2) Walcott, B., N. Claros, A. Patel and P.R. Brink 1998 Age-related decrease in innervation density of the lacrimal glands in mouse models of Sjögren’s Syndrome.

The Lacrimal Gland, Tear Film and Dry Eye Syndromes: Basic Science and Clinical Relevance Ed. D.A. Sullivan, Plenum Press pp 209-220

3) Brink, P.R., Peterson, E., Banach, K and Walcott, B 1998 Electrophysiological evidence for reduced water flow from lacrimal gland acinar epithelium of NZB/NZW F1 mice.

The Lacrimal Gland, Tear Film and Dry Eye Syndromes: Basic Science and Clinical Relevance Ed. D.A. Sullivan, Plenum Press pp 917-924

4) Walcott, B. 1998 The lacrimal gland and its veil of tears. News Physiol. Sci. 13: 97-103