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Peroxidase secretion by lacrimal glands from juvenile F344 rats
B B Bromberg1, M M Cripps, M H Welch
1Department of Biological Sciences, University of New Orleans, LA 70148.
Insights
Lacrimal gland peroxidase secretion decreases with age in rats. This study investigated age-related changes in protein and peroxidase secretion in response to cholinergic and adrenergic stimulation.
Area of Science:
- Biochemistry
- Physiology
- Ophthalmology
Background:
- Lacrimal gland peroxidase secretion is higher in juvenile rats than adults.
- Age-related changes in lacrimal gland function are not fully documented.
Purpose of the Study:
- To investigate age-related changes in lacrimal protein and peroxidase secretion.
- To examine the effects of muscarinic cholinergic and alpha-adrenergic stimulation on secretion in rats of varying ages.
Main Methods:
- Incubation of rat lacrimal tissue fragments in perifusion chambers.
- Measurement of protein and peroxidase secretion in response to carbachol and phenylephrine.
- Analysis of age-related correlations and dose-response curves.
Main Results:
- Total protein secretion showed a negative correlation with age.
- Peroxidase secretion in response to carbachol and phenylephrine significantly changed with age.
- Maximum peroxidase secretion was reduced by approximately 50% in older rats.
Conclusions:
- Age significantly impacts lacrimal gland peroxidase secretion in rats.
- Stimulation with carbachol and phenylephrine reveals age-dependent alterations in secretory responsiveness.
- Further research is needed to fully elucidate the mechanisms behind these age-related changes.
Abstract:
Secretion of peroxidase by rat lacrimal glands is generally acknowledged to be greater in juvenile rats than in adults. However, this phenomenon has not been so well documented in lacrimal glands as other age-related changes have been. Therefore, we studied lacrimal protein and peroxidase secretion in response to muscarinic cholinergic and alpha-adrenergic stimulation of glands from 35- to 90-day-old male F344 rats. Lacrimal tissue fragments were incubated in perifusion chambers, and secretion of protein and peroxidase was measured in response to stimulation by carbachol or phenylephrine. There was a negative first-order correlation between total protein secretion and age. Dose-response curves showed that at the highest doses there was a small but significant change in protein secretion. Secretion of lacrimal peroxidase in response to carbachol and phenylephrine changed significantly with increasing age. The tissue content of peroxidase was diminished by about 25% during this period, but that decrease alone was not sufficient to explain the changes in secretory responsiveness. The decrease of peroxidase secretion elicited by phenylephrine had both first- and second-order components in its correlation with age between 35 and 90 days. Dose-response curves for 5-week (35-41-day)- and 12-week (84-90-day)-old tissue showed that the maximum secretion of peroxidase was reduced by about 50%, but with no apparent shift in the dose-response curve.(ABSTRACT TRUNCATED AT 250 WORDS)