Postnatal development of the blood vasculature in the rat adrenal gland: a scanning electron microscope study of microcorrosion casts.

Postnatal development of the blood vasculature in the rat adrenal gland was examined with scanning electron microscopy (SEM), using a microcorrosion casting method. The cortical vascular bed on postnatal day 1 (P1) was incipient, consisting of an outer capillary layer and an inner sinusoidal vascular layer of the juxtamedullary zone. The vascular bed grew continuously with clearer zonal differentiation as the maturation proceeded. By P7 the outer capillary layer had differentiated into the vasculature of the glomerular and fascicular zone, while the juxtamedullary sinusoidal vascular layer had reduced its thickness to differentiate into the vasculature of the reticular zone. The neonatal adrenal vasculature consisted only of the cortico-medullary system. The medullary arteries and the medullary capillary bed were first observed on P14. The adrenomedulla thus came to receive a twofold blood supply by this time. Before the establishment of the medullary arterial system, the medulla appeared to receive its blood supply partly from the cortical capillaries and partly from the radial sinusoidal vessels passing through the cortical vascular bed. The radial sinusoidal vessels were suggested to differentiate into the cortical capillaries. The medullary arteries may originate from the vessels associated with chromaffin bodies incorporated into the adrenal gland or differentiate from the radial sinusoidal vessels. Histological changes, including cortical cell involution and hemorrhage occurring during the neonatal period, would seem to have crucial relevance to the remodeling of the adrenal vasculature.