Characteristics of the pituitary immunopositive ACTH cells in rat females after chronic exposure to constant light

Abstract

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.Ispitivani su efekti dugotrajnog izlaganja ženki Wistar pacova stalnom svetlu, na adrenokortikotropne (ACTH) ćelije. Eksperimentalne životinje stare 30 dana izlagane su konstantnom svetlu (600 luksa) tokom 95 dana. Kontrolne životinje odgovarajuće starosti su držane na normalnom, 12:12 h dnevno-noćnom režimu i sobnoj temperaturi. ACTH ćelije su imunohistohemijski bojene metodom peroksidaza-antiperoksidaza (PAP), a istovremeno je sakupljana krv za određivanje koncentracije ACTH u plazmi. Životinje izložene stalnom svetlu imale su za 22% povećane sve morfometrijske parametre ACTH ćelija merene tokom ovog rada (zapremina ćelija, njihovih jedara i volumenska gustina) u odnosu na kontrole i uočene razlike su bile statistički značajne (p < 0.05). Koncentracija ACTH u plazmi je takođe bila veća za 13% (p < 0.05) u odnosu na kontrolne vrednosti. Ovi rezultati ukazuju da dugotrajno izlaganje stalnom svetlu na specifičan način stimuliše rast i sekretornu aktivnost ne samo ACTH ćelija adenohipofize već i ćelija pars intermedia ženki pacova