Ultrastructural alterations in the liver parenchymal cells and thymus lymphocytes following the administration of hydrocortisone.

The early effect of the administration of hydrocortisone on the liver parenchymal cell and thymus lymphocyte was followed chronologically with respect to (a) the contents of nucleic acid and protein and (b) the ultrastructural integrity of the subcellular components. In the electron microscopic study, morphometric and stereographic techniques combined with statistical analysis were applied for the construction of size distribution curves of the mitochondria and nucleus. The injection of hydrocortisone, 1 mg/mouse, caused little change in the liver and a remarkable decrease of nucleic acid and protein content in the thymus from 12 through 48 hr. It was found that the distribution of sectional mitochondrial areas (in sq mp) approximates the log-normal curve for the six examples studied. The geometric mean of the liver mitochondrial sections significantly increased in size from 1 through 48 hr after the hormone injection. In spite of the marked enlargement of mitochondria, the integral crista structure and matrix substance were well preserved. Evidence indicates that these giant mitochondria are formed through fusion of smaller mitochondria within the cytoplasm. In the thymus, however, the same hormone caused an increased incidence of degenerative mitochondria with defective crista structure, reaching a peak at the 6th hr before thymic involution became manifest. The responses of nuclei to the hormone, as revealed in terms of the distribution of spherical nucleus diameter, were also prompt, but no differential characteristics were detected between the liver parenchymal cell and the thymus lymphocyte.