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Using light, electron microscopy and cytochemistry, the early (embryonic week 4-8) stages of adrenal gland (AG) development were studied in domestic pig. The interrelations between the cells of the fetal cortex (FC) and chromaffin cells (CC) were traced. At week 5, AG primordium is represented by FC, which consists of the epithelioid cells, with the ingrowing neural cords containing CC islets. Starting at the early embryonic period and up to fetal period, CC and interrenal cells of FC are closely interrelated with each other and sinusoidal capillaries. Both cellular types are at different stages of differentiation, including the functionally active elements. At weeks 7-8, FC cells undergo involution, while those ones, left at periphery, form definitive cortex. CC are located in the central part of the organ and form suprarenal tissue. Authors hypothesize, that CC, migrating into AG primordium, initially induce the development of interrenal primordium, and later cause the involution of FC. This, possibly, may be explained by the fact that further antenatal and postnatal development of the organism requires more corticosteroids than the amount produced by FC.

A study was made of the functional activity of the adrenal cortex in 15 1/2-, 18 1/2-, and 21 1/2-day rat fetuses and neonates. Adrenal tissue was incubated after its preliminary trypsinization at 37 degrees C for over 2 weeks with and without ACTH addition into the culture medium, in the amount of 0.1 U/ml. The corticosterone level was determined in the culture medium fluorimetrically. The activity of 3 beta-oxysteroid dehydrogenase was determined histochemically. Corticosterone was revealed in the culture medium. The activity of 3 beta-oxysteroid dehydrogenase was found in the cells of the cultivated adrenal glands. Addition of ACTH into the culture medium considerably increased the corticosterone level and elevated the activity of 3 beta-oxysteroid dehydrogenase. It can be considered on the basis of the aforesaid that cells of the primary culture of the adrenal cortex of rat fetuses aged 15 1/2-, 18 1/2-, and 21 1/2-days and of neonates could form, in the process of incubation, corticosterone from the endogenous substrates in the course of 11, 16, 8 and 13 cultivation days, respectively. The presence of ACTH in the culture medium for the adrenal glands of rat fetuses (of all the gestation periods under study) and of neonates intensified the steroidogenesis.

Aspartate aminotransferase was detected in the adrenals of 6-7-week human embryos, the activity being the highest at the 7-9th and 12-14th weeks. Alanine aminotransferase was found in 15-week foetuses. During all the period investigated (6-28 weeks), the activity of aspartate aminotransferase was found to be higher than that of the second enzyme. The activity of both enzymes is higher in female foetuses than in male ones. However, age changes in the activity of both enzymes in male embryos and foetuses were of the same sign as in female ones.

A study was made of lipid, cholesterol, and ascorbic acid content in the adrenal cortex of rabbit fetuses developing under conditions of normal pregnancy and under the action of hypoxic and hyperoxic exposures during its third trimester. It appeared that in normal pregnancy the adrenal cortex was activated, this being associated with the adaptive motor reactions of the developing fetus. The action of moderate hypoxic exposures led to a greater activation of moderate hypoxic exposures led to a greater activation of the adrenal cortex, this being expressed in a marked fall of lipid, cholesterol and ascorbic acid content. The weight of the total muscle mass and of the fetuses increased as a whole. The adrenal cortex became disactivated under conditions of the hyperoxic exposures; this is expressed in a marked increase in the content of the mentioned formations. The weight of the total mass and of the fetuses decreases.

By means of transmissive electron microscopy the adrenals have been studied in 25 human embryos and fetuses at the age of 6-36 weeks. Certain stages have been revealed in formation of the adrenal cortex microcirculatory bed. In 6-7-week-old embryos (period of diffuse protocapillary bed) endothelial structure and mesenchymal cells, surrounding the adrenal anlage, resemble one another. A distinguished feature of the endothelium is regularly revealed desmosomes and large vacuoles, often found in cytoplasm of endotheliocytes. In 8-12-week-old fetuses (period when the organospecific microcirculatory bed is forming) sinusoid capillaries differentiate in the internal zone of the adrenal cortex; in endothelium fenestrae, "hatches", "locks" are revealed, the capillary basal membrane is formed. During subsequent time of the intrauterine development perfection of the microcirculatory pathways in the adrenals takes place, the arteriolar link of the subcapsular layer including. By the time of birth morphofunctional maturity of the microcirculatory bed in the adrenal cortex is noted.

It was found in the experiments on adult males, descendants of the intact or adrenalectomized (prior to mating) female rats which were injected during the pregnancy with adrenaline, hydrocortisone or saline solution, that the reaction of their hypophysial-adrenocortical system to emotional stress or injection of noradrenaline into brain were inversely proportional to the content of corticosteroids, rather than of adrenaline, in the blood of their mothers during the pregnancy. On the other hand, the coupled changes of the levels of corticosteroids and adrenaline in the blood of pregnant mothers only was accompanied by the marked decrease in the sensitivity of brain cholinergic mechanisms in descendants. Hence, the changes of the levels of both adrenaline and corticosterids in the blood of pregnant females modify the reactivity of hypophysial-adrenocortical system of adult descendants, apparently, via the development of brain neurochemical mechanisms in the foetuses. But the role of these hormones is different.

The activity of 3beta-OH-steroid dehydrogenase in the adrenal cortex of 21-day fetuses in control and 3 days after decapitation in utero was estimated quantitatively by microspectrophotometry. The enzyme activity calculated as per conditioned cell in the fascicular zone exceeded that in the forming glomerular zone. After hypophysectomy the activity of the 3beta-OH-steroid dehydrogenase decreased in both the fascicular and glomerular zones.