Age- and gender-related influence on the lacrimal gland and tears

Previous research has demonstrated that distinct, gender-related differences exist in lacrimal glands in a variety of adult species. The objective of the current investigation was to examine whether this influence of gender extends throughout development and aging. Towards that end, morphological parameters of the lacrimal gland, as well as the volume, protein and IgG content of tears, were measured in male and female infant, preweanling, pubertal, adult, mid-life and senescent rats. Our results showed that dramatic, age-related variations occurred in the weight and morphological appearance of the lacrimal gland. Moreover, the magnitude of structural changes was dependent upon gender. Acinar area was significantly greater in lacrimal tissue of males, as compared to females, at all ages except pre-weanling; this sexual dimorphism was most evident in senescent rats. In contrast, acinar density in lacrimal glands of females was higher than, or equal to, that of males throughout development and aging. With regard to tears, pronounced increases were evident in tear volume, protein and IgG content from the pre-weanling stage to adulthood. After this time, these tear indices tended either to plateau or rise slightly until senescence. Gender had little or no impact of the volume of, or protein and IgG level in, tears. Of interest, the IgG/protein ratio in tears was 49- to 105-fold less than that found in lacrimal tissue, indicating that IgG moves down a gradient from the lacrimal gland to tears. Overall, our findings demonstrate that gender has a significant influence on lacrimal gland structure during development and aging. However, this impact is limited with respect to tear volume and protein content.