Histomorphometric examination of the pineal gland in foals and adult horses

Abstract

This study was conducted to evaluate the pineal glands of the foal and adult horses with histomorphometry. The pineal glands were sectioned at a thickness of 40 mu m and stained with AgNOR for stereological analyses. The weight and volume of the pineal gland as well as the number of pinealocytes were significantly higher in the adult horses (P=0.009). However, the number of pinealocytes in per volume was similar between foals and adult horses. Such data indicate that growth in the size of the gland is related to increase in the number of pinealocytes. The pinealocyte nucleus is significantly larger in adults (P=0.009). Such a size difference should be further investigated if it is due to an increase in the number of cells with increased DNA content. Melanin was distributed throughout the foal pineal gland whereas it was focally localized to connective tissue in adults. The different patterns in melanin distribution suggest that foals and adult horses may differ by means of melanin metabolism in the pineal gland.