Examination of the Effects of Pinealectomy upon Adrenal Structure in the White Rat

Abstract

The effects of pineal extirpation at three days and thirty days upon adrenal structure in male and female rats were examined. Animals were either reared in a diurnally lighted (12 : 12) environment or in total darkness; those pinealectomized at three days were sacrificed at either twenty or forty days, while those animals which were pinealectomized at thirty days were sacrificed at forty, sixty, eighty or one hundred days. Body weights were monitored at ten daily intervals. Pinealectomy did not initiate a consistently significant alteration in adrenal weight, adrenal diameter or in the depths of the adrenal cortical zones at any time when compared to unoperated and sham-operated control animals. In addition, no changes in the ultrastructural organisation of the adrenal cortex could be detected. Animals pinealectomized at thirty days and reared in total darkness possessed adrenals which were slightly lighter than those of light/dark reared animals. This difference became significant when adrenal diameters were compared. Pinealectomy did not induce a consistently significant alteration in rates of growth, although pinealectomized rats were often slightly heavier than unoperated and sham-operated controls. It was concluded that adrenal size is influenced by light, but that this influence is not directly mediated by the pineal gland. If, as has been suggested by several workers, the adrenal can be influenced by the pineal, this is probably not via a simple ACTH mechanism. In addition, the pineal does seem to exert a very slight retarding effect upon body weight increase.