Abstract
Abstract: :
Purpose:To determine if lacrimal gland morphology, neural innervation, and protein secretion changes with increasing age. Methods:Lacrimal glands were removed from 3, 12, 24, and 32 month-old, male, BALB/c mice. Lacrimal glands were fixed, sectioned and processed for histochemical and immunofluorescence techniques. Sections were stained with hematoxylin and eosin. Western blot and immunohistochemical analyses were performed using markers for parasympathetic and sympathetic nerves. For measurement of secretion, the lacrimal gland was dissected into small pieces that were incubated for 20 min. intervals in Krebs Ringer buffer containing 5mM KCl (control), 75mM KCl (depolarizing buffer to activate nerves), carbachol (a cholinergic agonist, 10-4 M) or phenylephrine (an α1-adrenergic agonist, 10-4 M). After incubation, the media were collected and the total amount of acetylcholine and peroxidase released into the media was analyzed using a spectrofluorometric assay. Results:With increasing age, progressive morphological changes occurred in the lacrimal gland including thickening of the connective tissue sheath, increased lymphocytic infiltration, and lobular and acinar atrophy. The density and distribution of parasympathetic and sympathetic nerves that surround acini decreased with increasing age. The pattern of innervation changed from widely spread punctate staining in 3 and 12 month-old animals to aggregated punctate staining surrounding acinar- and ductal-cells in 24 and 32 month-old animals. Release of acetylcholine from lacrimal gland nerves by depolarization decreased in 24 compared to 3 and 12 month-old animals. Similarly, carbachol- or phenylephrine-stimulated protein secretion decreased in lacrimal glands from 12-32 compared 3 month-old animals. Conclusion:In the lacrimal gland considerable structural alteration, decreased acetylcholine release, and decreased protein secretion occur with increasing age.
Keywords: 309 aging • 452 lacrimal gland • 490 neurotransmitters/neurotransmitter systems