Effects of hereditary hypopituitarism and ectopic pituitary transplants on pinealocytes of the mouse: a quantitative ultrastructural study.

The ultrastructure of the pinealocytes of Snell dwarf mice (dw/dw) was examined morphometrically and compared with that of both phenotypically normal (dw/+ or +/+) animals of the same strain and dwarf mice with ectopic pituitary grafts. Ultrastructural features characteristic of diminished activity of the pinealocytes were observed in dwarf mice as compared with controls. Ectopic pituitary grafts induced morphological signs of activation of the pinealocytes in this mutant. The results of the present study demonstrate the influence of the adenohypophysis on the pineal gland and these data, together with the known influence of the pineal gland on the adenohypophysis, support the existence of a reciprocal relationship between these two glands.