The fine structure of the newborn rat adrenal cortex

Summary The structural changes of the zona juxtamedullaris of the rat adrenal cortex at birth, have been examined by the light and the electron microscope. In this zone clusters of medullary cells lying among the strands of cortical tissue were observed. In the inner portion of the zona juxtamedullaris two types of adrenocortical cells were found: light and very-dark cells. The latter are smaller than the light cells and are always in close connection with the medullary tissue. The ultrastructural features of the very-dark cells suggest that these elements are in degeneration. This finding supports the hypothesis that at birth there is a partial degeneration of the rat zona juxtamedullaris, i.e. the zone corresponding to the fetal zone of some mammalian species.It is proposed that in all mammalian species at birth there is a partial regression of the zona juxtamedullaris and that the regression of the fetal zone is only the quantitative increase of this phenomenon. This hypothesis is discussed in relation to numerous data demonstrating that there are enzymatic conditions in the rat during fetal life, which permit a discrete hypertrophy of the adrenal cortex.The author wishes to express his appreciation to Dr. A. Gambino and to Mr. G. Gottardo for technical assistance.     

Lipid peroxidation in the adrenal cortex during exhausting stress

Under prolonged stress which is connected with exhaustion of functional resources of adrenal cortex the activation of lipid peroxidation processes in this gland was found. It is possible that the reason for such lipid peroxidation activation is the decrease in the content of adrenal cortex ascorbic acid and alpha-tocopherol.     

Primary response mechanisms of the adrenal cortex in dogs to pain stress]

The adrenal cortex of dogs shows a drop in the glucocorticoid content 10--15 sec after the pain action in the presence of the free cholesterol level increase and its esterified form drop. The concentrations of hormones in the blood falls chiefly at the expense of protein bound hydrocortisone. The subsequent phase of the reaction (after 30--60 sec) is characterized by a considerable accumulation of the hormones by the gland. The level of free glucocorticoids significantly increases, the initial ratio of hydrocortisone and cortisone restores, and transcortin depot is filled up. The role of the adrenal and transcortine depot in realization of feedback mechanisms under stress is discussed.     

Quantitative evaluation of ultrastructural restructuring in the adrenal cortex of rats under stress

Quantitative and qualitative analysis has revealed that submicroscopic changes of the rat adrenal cortex in dynamics of the stress reaction examined at the level of "functional element" which combines basic structural components of the parenchyma and stroma are of the polyphase character and agree with data from the biochemical analysis of 11-OCS in blood plasma. At the stage of exhaustion of the stress reaction (72 hours of immobilization) the ultrastructure of the adrenal cortex testifies to the preservation of functional reserves in the secretory cells.     

Dynamics of lipid peroxidation and steroidogenesis in adrenal cortex during stress

The phase character of lipid peroxidation has been found in the rabbit adrenal cortex in the process of adaptation to extreme loads. Under acute stress the activation of lipid peroxidation is directly dependent on the hormonal synthesis processes. Under conditions of the prolonged stress factor an enhancement of the lipid peroxidation intensity in the adrenal cortex coincides with a decrease in the steroidogenesis rate.     

Effect of cholesterol administration on the state of the adrenal cortex in severe stress

The two weeks' effect of cholesterol on the rat adrenal cortex response under conditions of a severe stress was studied. In comparison with control, the degree of the gland activation and its alteration was found to decrease. It is suggested that the effect of cholesterol depends upon the action on the hypothalamus, and upon the adrenocortical tissue as well. The action of cholesterol on the adrenocortical tissue is bound with the cholesterol capacity to retard peroxydation reactions.     

Effect of alpha-tocopherol on adrenal cortex functions under stress]

alpha-Tocopherol has been studied for its effect on lipid peroxidation and steroidogenesis in the adrenal cortices of rat and rabbit under stress. The vitamin is shown to exert an inhibitory effect on the lipid peroxidation developing under chronic stress. A biphasic pattern of the alpha-tocopherol effect on the steroidogenesis in the adrenal cortex is established: a decrease in the release of the steroids under the acute stress and maintaining of their levels under the chronic stress. A conclusion is drawn about a potential alpha-tocopherol application to correct the adrenal cortex function under stress.