CHARACTERISTICS OF THE PITUITARY IMMUNOPOSITIVE ACTH CELLS IN RAT FEMALES AFTER CHRONIC EXPOSURE TO CONSTANT LIGHT

Abstract

Summary: The effects of chronic exposure to light of adult female Wistar rats on growth and function of pituitary adrenocorticotropes (ACTH cells) were examined. The animals were exposed to continuous light of 600 lux for 95 days, starting on day 30 of age. Control rats were kept under a 12:12 h light-dark cycle, at ambient temperature. ACTH-producing cells were studied using the peroxidase-antiperoxidase immunohistochemical procedure and blood samples were collected for hormone analyses. In animals exposed to a chronic light-treatment all morphometric parameters measured throughout the present study i.e.: ACTH cell volume, nuclear volume and relative volume density were increased by 22% and the differences between this group and the controls were statistically significant (p<0.05). The concentration of plasma ACTH was elevated by 13% in light-exposed group in comparison with the control and this difference was statistically significant (p<0.05), as well. These findings suggest that continuous exposure to light is specifically involved in growth and secretory activity of ACTH cells of adenohypophysis of rat females.