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Insulin-like growth factor I (IGF-I) is required for the maintenance of differentiated functions of bovine adrenal fasciculata cells in culture. We have investigated, by immunocytochemistry, the presence of IGF-I in cells cultured in the absence or presence of corticotropin (ACTH) and angiotensin II (A-II), as well as the secretion of IFG-I and its binding proteins (IGF-BP). In control cultures, very few cells were specifically stained with the anti-IGF-I serum. Following 2 days treatment with A-II (10(-6)M) or ACTH (10(-8)M) the number of stained cells increased 5 and 14 fold, respectively. In all cases the staining was specific since it was abolished when non-immune rabbit serum replaced the anti-IGF serum or when the anti-IGF-I serum was preincubated with saturating concentrations of the peptide. Under the same experimental conditions the secretion of IGF-I in the medium, evaluated by a specific radioimmunoassay, was increased 2- and 7-fold by A-II and ACTH, respectively. Using the method of western ligand blot, we found that the major form of IGF-BP secreted by control adrenal cells is a 38-42 kDa doublet protein. Two minor forms with apparent mol wt of 28-31 kDa and 24 kDa have also been identified. Following acid-ethanol extraction of the conditioned medium all the IGF-BP were recovered in the pellet, whereas most of the IGF-I was in the supernatant. ACTH and, to a lesser extent.(ABSTRACT TRUNCATED AT 250 WORDS)

Steroidogenic cells (adrenal, gonads and placenta) utilize cholesterol as a substrate for hormonal biosynthesis. Cholesterol can be synthetized de novo acetate or can enter the cell as a component of plasma lipoproteins, particularly LDL (low density lipoprotein) and HDL (high density lipoprotein). Steroidogenic cells utilize predominantly lipoproteins. Lipoprotein-cholesterol enters the cell by a specific pathway: binding of lipoproteins, particularly LDL to a membrane specific receptor and internalization of the complex receptor-lipoprotein, followed by dissociation of the complex; the receptor is reutilized, while LDL is hydrolyzed by lysosomal enzymes in amino-acids and free cholesterol. The liberated cholesterol is available for utilization by the cell. In addition, lipoproteins modulate intra-cellular cholesterol metabolism via two enzymatic activities; inhibition of hydroxymethyl-glutaryl coenzyme A reductase activity (HMG CoA reductase) which controls the rate limiting step of cholesterol biosynthesis, and stimulation of acyl CoA cholesterol acyltransferase (ACAT) activity which controls the esterification of cholesterol, before its translocation to lipids droplets. Peptide hormones LH/hCG and ACTH regulate lipoproteins metabolism in their target tissues by increasing LDL receptors number, a way which allow more cholesterol to enter the cell. The role of lipoproteins on steroidogenesis has been studied predominantly in adrenal and to a lesser extent in ovary and placenta and poorly in testis. Using a model of cultured porcine Leydig cells, we have demonstrated that de novo synthesis of cholesterol accounts for only 25% of the maximal steroidogenic capacity of these cells. Moreover the effects of lipoprotein LDL was synergistic with that of gonadotropins.

Rat testicular cytosol binds specificity dexamethasone (KD = 5 X 10(=9)M). After incubation of testicular slices with 3H-dexamethasone, at 30 degrees C for 2 hours most of the intracellular radioactivity is found inthe nuclei. Administration of h CG at pharmacological doses for three days to male rat during puberty increases plasma testosterone levels and 3H-thymidine incorporation into testicular DNA. Simultaneous administration of dexamethasone partially blocks both effects of hCG. These results suggest that interaction of glucocorticoïds with specific receptors controls both the specific function and the cells multiplication of rat Leydig cells.

A 31 years old man with an adrenocortical carcinoma was studied. Clinically he had a bilateral and recidiving gynecomastia and showed high urinary oestrogens, 17 cetosteroids, tetra-hydro-desoxy-cortisol and pregnandiol excretion with normal cortisol production. A partial increase on ACTH, no suppression on dexamethasone and no variation on HCG administration were observed. The surgical resection of the tumor normalized this urinary excretion. The serum dehydro-epiandrosterone (DHEA) and sulfate (DHEAS), oestrone, oestradiol, androstenedione (A) levels were greatly elevated. No variations of the cortisol, A, DHEA and DHEAS was noted after ACTH injection. In vitro the lack of ACTH's action was related to an anomaly of ACTH receptor with normal protein kinase activity.

Corticotropin (ACTH) has two main actions in mammalian adrenal cortex: acute stimulation of glucocorticoids secretion and trophic effect which allow the expression of genes encoding for the steroidogenic enzymes. The ACTH membrane bound receptor was one of the first to be demonstrated by direct binding of labeled hormone to subcellular preparations of the adrenal cortex. However, detection and characterization of physiological relevance to ACTH receptors has been difficult, because of the low biological activity of the labeled ACTH. Introduction of a bulky iodine atom into Tyr2 and the oxidation of Met4 appear to contribute most to the loss of activity. These difficulties were overcome recently by using an [125I]-ACTH labeled only in Tyr23, which retains full biological activity. Using this labeled hormone, physiologically relevant ACTH receptors, with high affinity (KD congruent to 10-10M) and low capacity (congruent to 2000 sites/cell) have been characterized in several mammals. A second site of low affinity (KD congruent to 10(-7M) and high capacity, has been found in some studies but the significance of this second site is unknown since it cannot be related to any physiological response of adrenal cells to ACTH. In contrast with the loss of receptors and desensitization of target cells caused by most polypeptide hormones, ACTH seems to regulate positively its own receptors and the cAMP response. The molecular weight of the ACTH receptor appears to be between 83 and 100 KD.(ABSTRACT TRUNCATED AT 250 WORDS)