Androgen control of secretory component mRNA levels in the rat lacrimal gland.
The purpose of this investigation was to determine whether the known gender-related differences in, and the endocrine control of, the production of secretory component (SC) by the rat lacrimal gland are associated with alterations in SC mRNA content. Levels of SC mRNA were measured in lacrimal tissues of intact, sham-operated, castrated, hypophysectomized, and testosterone-treated male and female adult rats by Northern blot procedures, which utilized a specific, [alpha-32P]-labelled rat SC cDNA probe. For control purposes, SC mRNA amounts were standardized to the beta-actin content in experimental blots. The location of SC mRNA in lacrimal glands was evaluated by in situ hybridization techniques, which involved exposure of tissue sections to sense or anti-sense [35S]-labelled SC RNA probes. Our results demonstrate that: (1) lacrimal glands of male rats contain a significantly greater amount of SC mRNA than those of female rats, and that this difference co-exists with distinct, gender-associated variations in the distribution of SC mRNA in lacrimal tissue; (2) orchiectomy or hypophysectomy, but not ovariectomy or sham surgery, leads to a marked decline in the lacrimal SC mRNA content; and (3) testosterone, but not placebo, administration to castrated male and female rats induces a significant increase in the SC mRNA levels in lacrimal tissue. Overall, these findings show that gender, androgens and the hypothalamic-pituitary axis exert a considerable influence on the SC mRNA content in the rat lacrimal gland.