Epithelia & Membrane Transport

Abstract

Keratoconjunctivitis sicca is associated with progressive pathological alterations in glandular and extra-glandular tissues resulting in a decrease in tear secretion (Nelson, 1998). It is an age-related disorder affecting mainly the middle aged and the elderly. Age-related changes in both the physiological and morphological properties of the lacrimal gland have previously been observed (Draper et al. 1997 a). These included a reduction in protein secretion from aged lacrimal gland acini compared with that from young tissue. Morphologically, the aged tissue displayed structural damage and changes in acini type and distribution within the gland (Draper et al. 1997 b). However, little is known about cellular changes at intermediate age groups. This study investigates in more detail changes and distribution of the lacrimal acini in glands from male rats of 3-5,9, 12, 20, 24 and 28 months of age. The study employs light and electron microscopy and investigates changes within the lacrimal acini.Acini were counted from random sections at x 40 magnification using light microscopy and the percentage distribution of each acini type was calculated. In young glands (3-5 months) 81'2 ± 4'7 % (mean ± S.E.M., n = 40) of the acini were serous (protein-secreting cells). By 9 months this was significantly reduced to 50'5 ± 9'4 % (ANOV A; P < 0'05, n = 40) and by 12 months signif,icantly reduced to 19'5 ± 5'2% (P < 0'01, n = 40). The proportion of serous acini remained unchanged by 20 and 24 months, but by 28 months there was a further significant reduction to 7'6 ± 4'3 % (P < 0'05, n = 40). In young glands 17'2 ± 2'2 % (n = 40) of the acini were seromucous (proteinand mucous-secreting acini), by 9 months this significantly increased to 32'5 ± 3'3 % (P < 0'05, n = 40) and by 12 months increased significantly to 65'7 ± 4'4 %. By 20 months there was a slight decrease in seromucous acini to 53'3 ± 6'0% (n = 40); moreover, by 24 months there was a significant reduction to 29'3 ± 3'7 % (P < 0'01, n = 40) with a small increase at 28 months to 37'1 ± 3' 2 % (n = 40). Only 1'6 ± 0'4 % of the acini in young glands were mucous.Journal of Physiology (1998) 513.P By 9 and 12 months this increased significantly to 17'0 ± 1'9% and 15'8 ± 2'4%, respectively (P < 0'05, n = 40), and there was no significant change by 20 months. By 24 and 28 months, however, there were significant increases in mucous acini to 46'6 ± 5' 6 % (n = 40) and 55'3 ± 5'0% (n = 40), respectively. Lacrimal gland sections from young (3-5 months) and aged (20 and 24 months) rats were stained with Alcian Blue (Lev & Spicer, 1964) at pH l' 0 to stain for mucous acini. There was no staining of acini in young glands, indicating that there are little or no mucous acini at this stage, but there was specific staining of mucous acini in glands from the two aged groups. Staining did not occur at pH 2'5 nor at pH 4'0, indicating that the mucous secretion in the rat lacrimal acini is of moderately acidic mucosubstances. EM studies revealed serous acini of both 3-to 5-and 9-month-old glan...