Ascorbic acid accumulation by cultured rat adrenocortical cells

Water-immersion restraint stress disrupts nonenzymatic antioxidant defense systems through rapid and continuous ascorbic acid depletion in the adrenal gland of rats

We examined whether water-immersion restraint stress (WIRS) disrupts nonenzymatic antioxidant defense systems through ascorbic acid depletion in the adrenal gland of rats. Rats were exposed to WIRS for 0.5, 1.5, 3 or 6 h. WIRS increased serum adrenocorticotropic hormone, corticosterone and glucose concentrations and adrenal corticosterone content at each time point. WIRS increased adrenal lipid peroxide content at 3 and 6 h, and the increase was twofold higher than the unstressed level at 6 h. WIRS decreased adrenal ascorbic acid content at each time point, and the decrease reached one-third of the unstressed level at 6 h. WIRS increased adrenal reduced glutathione content at 0.5 and 6 h but reduced that content to half of the unstressed level at 6 h. WIRS increased adrenal α-tocopherol content at 1.5 h but returned that content to the unstressed level thereafter. When rats with 6 h of WIRS was orally preadministered with l-ascorbic acid (250 mg/kg), WIRS-induced changes in adrenal lipid peroxide, ascorbic acid and reduced glutathione contents were attenuated without any change in stress response. These results indicate that WIRS disrupts nonenzymatic antioxidant defense systems through rapid and continuous ascorbic acid depletion in the adrenal gland of rats.

Calcium and reactive oxygen species as messengers in endotoxin action on adrenocortical cells

The effect of Escherichia coli 0111:B4 endotoxin (lipopolysaccharide, LPS) on the intracellular Ca2+ and reactive oxygen metabolite content of both rat isolated fasciculata-reticularis and glomerulosa cells was evaluated by flow cytometry to know the role of these mechanisms in the initiation of cell injury produced by LPS on adrenocortical cells during endotoxic shock. A rapid increase of intracellular calcium was induced by endotoxin in both cell types. In fasciculata-reticularis cells, this [Ca2+]i increase was mainly due to an important mobilization of intracellular stores. Dose-dependent increases in [Ca2+]i were also observed when both cell types were incubated with LPS for 20 min in the presence of extracellular calcium. This treatment abolished the increase in intracellular calcium induced by ACTH and angiotensin II. On the other hand, the endotoxin produced a fast and dose-dependent increase in reactive oxygen species in both cell types, higher in glomerulosa than in fasciculata-reticularis cells. LPS-pretreated cells showed more susceptibility to the oxidative stress induced by Fe2+. These results can be related to functional alterations previously described showing the involvement of calcium and reactive oxygen species as messengers in the endotoxin action on adrenocortical cells.

Density separation of rat adrenocortical cells: morphology, steroidogenesis, and P-450scc expression in primary culture

We have developed a method that separates rat adrenocortical cells by density into populations which retain zone specific properties in primary culture. Two different parenchymal populations were obtained and designated 2FASC (1.034 g/ml, 18.0 microns cell diameter) and 7GLOM (1.069 g/ml, 11.7 microns cell diameter). In freshly isolated cell suspensions the physical characteristics and differential steroidogenic responses to adrenocorticotropin and angiotensin II suggested that 2FASC cells originated predominantly from the zona fasciculata and 7GLOM cells from the zona glomerulosa. In primary culture (Dulbecco's Modified Eagle's Medium-F12 medium with 15% horse serum and 2.5% fetal bovine serum) the two populations exhibited different morphologies. 2FASC cells retained lipid and formed cohesive epithelial monolayers that remained stationary for 3 wk. 7GLOM cells were initially epithelial but rapidly lost lipid, spread, and assumed fibroblastic shapes. Both cell types were positive for the cholesterol side-chain cleavage cytochrome P-450 by immunofluorescence. Therefore, the morphologic changes seen in 7GLOM cultures were due to modulation, not fibroblastic overgrowth. This phenotypic plasticity may reflect the mesodermal origin of the adrenal cortex, and the subcapsular location of 7GLOM cells in vivo. In contrast, cells such as 2FASC which are located deeper in the cortex seem to have a more restricted, fully committed parenchymal phenotype.

Metabolism and toxicity of xenobiotics in the adrenal cortex, with particular reference to 7,12-dimethylbenz(a)anthracene

The adrenal cortex contains high amounts of detoxifying enzymes, as well as generators and protectors of reactive oxygen species. The high content of cytochrome P-450 enzymes in the adrenal cortex together with its remarkable tendency to accumulate hydrophobic substances probably contributes to the extraordinary vulnerability of the gland to a number of xenobiotics. The best studied adrenocorticolytic compounds are the potent carcinogen 7,12-dimethylbenz(a)anthracene (DMBA) and its liver metabolite 7-hydroxymethyl-12-methylbenz(a)anthracene (7-OHM-12-MBA). Adrenocorticolysis generated by these agents in vivo as well as in vitro demonstrates high regioselective requirements and is strongly influenced by the presence of ACTH, steroids, cytochrome P-450 inhibitors and antioxidants. Furthermore, 7-OHM-12-MBA has been demonstrated to uniquely generate selective and massive oxidation of mitochondrial glutathione in cultured rat adrenal cells. The DMBA-induced adrenocorticolysis is thoroughly discussed in this review with particular emphasis on the metabolism of DMBA and the influence of various effectors. A working hypothesis involving a possible peroxidative mechanism is also presented.