Effect of Ocular Enucleation and Altered Lighting Regimens at Various Ages on Adrenal and Gonadal Weight and Mean Plasma Corticosteroid Levels in the Rat

Abstract

Adrenal, ovarian and body weight, and mean plasma corticosteroid levels were determined in 30 and 80 day old rats which had either been enucleated at various ages (1, 14 or 30 days) or raised under varying conditions of exposure to constant light (CL) or constant dark (CD). CL or CD was maintained, (a) from birth until time of sacrifice, (b) from birth until 14 or 30 days of age with transfer to normal light-dark until sacrifice, (c) from 14, 30 or 60 days of age (prior rearing in normal light-dark) until sacrifice. Effects of such experimental conditions varied with sex and the age at which altered lighting was begun and terminated. A given lighting regimen could be associated with opposite directions of change in adrenal and gonadal weight.

1. Gonadal weight: Male animals reared in CD had decreased gonadal weight at 30 d. of age, but increased gonadal weight at 80 days. Female gonadal weight was unaffected by CD. 80 d. female animals who had been exposed to periods of CL somewhere between 14 and 30 d. of age (but not those permanently reared in CL) had increased ovarian weight. Testicular weight was unaffected by any schedule of CL exposure.

2. Adrenal weight and plasma corticosteroid levels: Adult animals of both sexes exposed to intermittent periods of CL manifested decreased adrenal weight and tended to have increased mean plasma corticosteroid levels, whereas permanent rearing in CL had no effect. Animals exposed permanently or intermittently to CD had decreased mean plasma corticosteroid levels but no change in adrenal weight. There was no correlation between changes in these two adrenal variables and alterations in circadian periodicity of plasma corticosteroid levels. (1)

3. Ocular enucleation in contrast to CD regimens had no effect on adrenal or gonadal weight or mean plasma corticosteroid levels.