Adrenal cells in tissue culture. 3. Effect of adrenocorticotropin and 3',5'-cyclic adenosine monophosphate on 11 beta-hydroxylase and other steroidogenic enzymes

11β-Hydroxyandrostenedione: Downstream metabolism by 11βHSD, 17βHSD and SRD5A produces novel substrates in familiar pathways

11β-Hydroxyandrostenedione (11OHA4), a major C19 steroid produced by the adrenal, was first reported in the 1950s. Initially the subject of numerous studies, interest dwindled due to the apparent lack of physiological function and, by the end of the century, 11OHA4 was no longer considered as an adrenal C19 steroid. Our recent studies, however, showed that 11OHA4 is the precursor to novel active androgens which include 11-ketodihydrotestosterone (11KDHT) which has been implicated in prostate cancer, thereby renewing interest in 11OHA4. In this paper we review the biosynthesis and downstream metabolism of 11OHA4. We discuss the extra-adrenal biosynthesis of 11OHA4 in humans and in other species, highlighting the well-documented role of 11OHA4 in the testes of male fish in which the steroid functions as an active androgen. Finally, we discuss the physiological relevance of 11OHA4 metabolism in castration resistant prostate cancer and outline future prospects.

Effect of copper chloride on adrenocortical activities in adult and immature male rats

Although copper is an important biological trace element required for normal metabolism, occupational exposure to copper in different industrial workers may result in abnormal rise in plasma copper level which can bring about adverse effects. Intraperitoneal injection of copper chloride at the dose of 2000 μg/kg per day and higher doses for 26 days resulted in significant rise in adrenal weight, adrenal Δ(5)-3β hydroxysteroid dehydrogenase (HSD) activity and serum corticosterone level in both adult and immature male rats, while 1000 μg/kg per day dose for 26 days duration did not significantly alter the adrenocortical activities and adrenal weight in adult rats. On the contrary, the latter lower dose caused a significant decrease in adrenal Δ(5) 3β HSD activity and serum corticosterone level in immature male rats.

18-hydroxylation in the Y-1 adrenal cell line: response to ACTH and to culture conditions

The 18-hydroxylation of deoxycorticosterone in the Y-1 adrenal cell line was studied under various incubation and cell culture conditions and compared to 11 beta-hydroxylation. Repeated incubation of the substrate increased both 18- and 11 beta-hydroxylation in the Y-1 cells. Furthermore, both 18- and 11 beta-hydroxylation were increased with increased serum concentration and prolonged incubation time. While the increase in 11 beta-hydroxylation seemed to be independent of the type of serum, 18-hydroxylation was much more important in cells cultured in fetal or newborn calf serum supplemented medium than in those cultured in horse serum supplemented medium. As expected, ACTH treatment increased 11 beta-hydroxylation; however, it decreased 18-hydroxylation. The different regulation of these two hydroxylating pathways by ACTH, point to a heterogeneity of the cytochrome P-450(11) beta of the Y-1 cell line.

Distinctive properties of adrenal cortex mitochondria

The mitochondria in cells that synthesize steroid hormones not only have enzymes not present in mitochondria of non-steroidogenic cells but also have unique mechanisms for regulating the steroid substrate availability for certain of these enzymes. We have considered in detail the cytochrome P-450scc system that is located in the inner mitochondrial membrane and that catalyzes the initial and rate-determining step in the steroid hormone biosynthetic pathway. The flux through this pathway is regulated both by the levels of these catalysts themselves and by the availability of the substrate cholesterol for conversion to pregnenolone. These two levels of regulation occur in different time frames but are both controlled externally by the action of tissue-specific peptide hormone. We have used the adrenal cortex fasciculata cells as our paradigmatic cell type. The overall picture seems closely similar for mitochondria in other such steroidogenic cells when analogous data are available. Thus, in adrenal cortex fasciculata cells ACTH triggers several long-term (trophic) and short-term (acute) effects upon and within mitochondria that influence the initial and rate-determining step in the steroid hormone biosynthetic pathway. The only second messenger for both effects characterized thus far is cAMP. An increase in membrane-associated cAMP rapidly activates cAMP-dependent protein kinase, which in turn phosphorylates several cellular proteins, e.g., cholesterol ester hydrolase (vide supra). The trophic action, i.e., that produced by exposure of the cells to increased levels of ACTH or cAMP for a prolonged period (minutes to hours), increases the amounts of the steroid hormone synthesizing proteins in the mitochondria by increasing the transcription of the relevant nuclear genes. This latter process is not needed for the acute increase in the rate of steroid hormone biosynthesis. Whether induction of steroidogenic enzymes requires activation of a kinase has not been determined. However, the postulated SHIP proteins provide a mechanism by which cAMP levels and protein synthesis itself may regulate this induction. Mitochondria in steroidogenic tissues exert control over this process by their ability to recognize, import and process correctly the nuclear encoded precursors of the steroidogenic enzymes. Whether control at this level is ultimately dictated by nuclear or mitochondrial gene products or by an interplay between them is still unknown.(ABSTRACT TRUNCATED AT 400 WORDS)

Regulation of steroid hydroxylase gene expression is multifactorial in nature

In summary, regulation of steroid hydroxylase gene expression is complex and multifactorial, involving cAMP-dependent and -independent mechanisms required for maintenance of optimal steroidogenic capacity, tissue-specific mechanisms which lead to different steroidogenic pathways in different tissues, and developmental mechanisms which lead to fetal imprinting of steroid hydroxylase expression and which probably overlap with both maintenance and tissue-specific mechanisms. Future studies will involve identification of the trans-acting factors associated with each of these aspects of the multifactorial regulation and characterization of the cis-regulatory elements to which they bind. Such studies will inevitably lead to the identification of genes encoding these trans-acting factors and investigation of their regulation. In this way, it will be possible to work outward from the steroid hydroxylase genes toward the cell surface receptors in order to elucidate the series of events which lead to cAMP-dependent and -independent regulation of steroid hydroxylase gene expression.

Corticotropin-induced changes in enzymatic activities of the post-pregnenolone steroidogenic pathway in rabbit adrenocortical cells

In an attempt to delineate the effect of corticotropin (ACTH) on post-pregnenolone steroidogenesis, the activity of enzymatic systems operative in conversion of pregnenolone into glucocorticoids and androgens was studied in adrenocortical cells from control rabbits and from animals treated with ACTH for 12 days (ACTH 1-24, 200 micrograms s.c. daily). The cells from ACTH-treated rabbits exhibited an increased overall steroidogenic capacity and produced much more cortisol (P less than 0.0005) as well as other 17-hydroxylated steroids as a result of increased activity of 17 alpha-hydroxylase; corticosterone generation was concomitantly reduced. The increased conversion of pregnenolone or progesterone into androgens, as a result of previous treatment with ACTH, provides additional evidence for an effect of ACTH on 17 alpha-hydroxylase activity. A stimulatory effect of ACTH on 11 beta-hydroxylase was also evidenced by these cells, since conversion of 11-deoxycortisol into cortisol was enhanced (P less than 0.005). The increased production of androgens from 17-hydroxylated precursors by cells from ACTH-treated rabbits suggests that ACTH also exerts a prolonged stimulatory effect on 17,20-lyase. The activity of 3 beta-hydroxysteroid dehydrogenase-isomerase was apparently not influenced by chronic treatment with ACTH, judged from unchanged conversion of dehydroepiandrosterone into androstenedione. The activity of 11 beta-dehydrogenase was likewise unchanged in these conditions.

The adrenal gland of stranded whales (Kogia breviceps and Mesoplodon europaeus): in vitro modulation of mitochondrial steroid enzyme activities

The effects of adrenocorticotropic hormone (ACTH), cyclic AMP (cAMP), NADPH, Krebs cycle intermediates (KCl), and metyrapone on the two key mitochondrial reactions in the biosynthesis of glucocorticoids--11 beta-hydroxylation and cholesterol cleavage--were studied in preparations from the adrenal glands of stranded whales (Kogia breviceps and Mesoplodon europaeus) and some terrestrial mammals. ACTH (30 pM) and cAMP (1.0 mM) enhanced the 11 beta-hydroxylation of [11-3H]deoxycorticosterone ([3H]DOC) in monolayer cultures of whale adrenal cells during a 4-hr incubation period. Mitochondria from whale and beef adrenals responded in a similar dose-related fashion to NADPH generated by the addition of increasing amounts of NADP (0-0.6 mM) to the in vitro system: at each level of NADPH, 11 beta-hydroxylation of [14C]DOC was several-fold greater than the cleavage of [14C]cholesterol. Metyrapone interfered in a dose-related manner with both the 11 beta-hydroxylation of [14C]DOC and the cleavage of [14C]cholesterol by mitochondria from whale and beef adrenals; inhibition of 11 beta-hydroxylation exceeded 60% at 0.1 mM metyrapone and was virtually complete at 1.0 mM in both species, while inhibition of [14C]cholesterol cleavage averaged 25% at 0.1 mM metyrapone and 50% at 1.0 mM. The effect of exogenous NADPH in supporting the 11 beta-hydroxylation of [14C]DOC could be maintained in beef and rat adrenal mitochondria to the extent of 70-100% by substitution with any of the KCl. This phenomenon was not found in similar whale studies where the KCl were all ineffective.(ABSTRACT TRUNCATED AT 250 WORDS)

Biosynthesis of (20S)-20 alpha-reduced steroids simultaneously with corticosteroids in primary cultures of newborn rat adrenocortical cells stimulated by ACTH

Newborn rat adrenal cells in primary culture produce corticosteroid hormones and (20S)-20 alpha-reduced progesterone metabolites in amounts which depend on ACTH concentrations and stimulation time. Eight (20S)-20 alpha-reduced progesterone metabolites, including 18-hydroxy-(20S)-20 alpha-dihydroprogesterone, were identified by comparison of their data in high performance liquid chromatography and in gas chromatography-mass spectrometry to those of existing or newly synthesized reference steroids. Quantitative studies of individual steroid biosynthesis were also performed using high performance liquid chromatography and gas chromatography. Several experiments were made without ACTH and with different concentrations of ACTH for periods of more than 3 weeks. The importance of the two main steroidogenic pathways, corticosteroid biosynthesis and progesterone reductive metabolism was modified by ACTH stimulation of the cultured cells. The progesterone reductive metabolism, important without ACTH and in the first days of ACTH stimulation, was decreased by 6.6 mU of ACTH/ml or higher concentrations but remained active throughout the life span of the stimulated cell cultures.

Chronic treatment with corticotropin increases the capacity of rabbit adrenocortical cells to convert pregnenolone into androgens

The present study was conducted to evaluate whether the previously demonstrated enhancement in adrenocortical androgen secretion in rabbits chronically treated with ACTH results, in addition to an increased pregnenolone production, from a more efficient conversion of this precursor of steroidogenesis into androgens. To this end, the adrenocortical cells from 14 control and 14 ACTH-treated rabbits (ACTH 1-24,200 micrograms s.c. daily for 12 days) were incubated either in the presence of different concentration of ACTH or with pregnenolone added in amounts from 0.5 to 250 micrograms. The total steroidogenic potency (maximal response to ACTH) was significantly enhanced for cells from ACTH-treated animals, as was the ACTH-induced production of dehydroepiandrosterone (DHEA), DHEA-sulfate, androstenedione and testosterone. In addition the production of these androgens from given amounts of exogenous pregnenolone was also significantly increased. The maximal capacity of adrenocortical cells to convert pregnenolone into androgens averaged (for ACTH-treated vs control group) 130 +/- 34 vs 43 +/- 10 pmol for DHEA, 138 +/- 43 vs 46 +/- 14 pmol for DHEA-sulfate, 99 +/- 31 vs 10 +/- 2 pmol for androstenedione and 8.0 +/- 2.6 vs 2.4 +/- 0.3 pmol for testosterone (P less than 0.001 for all androgens). The addition of ACTH to adrenocortical cells incubated with pregnenolone did not modify the maximal capacity of conversion of pregnenolone into androgens, which was in both experimental groups similar to that documented in the absence of ACTH. Thus, while an acute stimulatory effect of ACTH on adrenocortical steroidogenesis is devoid of any influence on the activity of the post-pregnenolone pathway of androgen synthesis, the chronic exposure of adrenocortical cells to ACTH lead to increased activity of steroidogenic pathway involved in the conversion of pregnenolone into androgens.

Enhanced androgen production by rabbit adrenocortical cells stimulated chronically with corticotropin: evidence for increased 17 alpha-hydroxylase activity

The effects of prolonged treatment with corticotropin (ACTH1-24, 200 micrograms s.c. daily during 12 days) on the production of androgens and glucocorticoids were studied on rabbit dispersed adrenocortical cells. The steroidogenic capacity of adrenocortical cells, expressed in terms of the maximal response to ACTH of glucocorticoid (i.e. corticosterone and cortisol) production, was significantly increased after treatment with ACTH. This was associated with a loss of sensitivity to this peptide: indeed, the concentration of ACTH required to induce a half maximal secretory response was one order of magnitude higher with cells from ACTH-treated animals. Among the C21 steroids measured the changes observed involved the 17 alpha-hydroxylated compounds (cortisol, cortisone, 11-deoxycortisol) while corticosterone production was significantly depressed. This effect of prolonged ACTH treatment on steroidogenic pathways involving 17 alpha-hydroxylation, was further evidenced by a clear-cut enhancement in androgen secretion (dehydroepiandrosterone, androstenedione and testosterone) by adrenocortical cells from ACTH-treated animals. The changes observed after treatment of the animal with ACTH were equally obvious, whether the adrenocortical cells were incubated with ACTH or with dibutyryl-c-AMP.

Expression of murine 21-hydroxylase in mouse adrenal glands and in transfected Y1 adrenocortical tumor cells

The S region of the murine major histocompatibility complex contains two structurally related genes (21-OHase A and 21-OHase B) that encode 21-hydroxylase (21-OHase), an enzyme essential for the synthesis of adrenal steroids. Expression of these two genes has been analyzed by using oligonucleotide probes specific for the 21-OHase A and B genes and by DNA-mediated gene transfer. Hybridization of the oligonucleotides to blots of BALB/c adrenal RNA demonstrated that all 21-OHase mRNA is derived from the 21-OHase A gene. Cosmids bearing either the 21-OHase A or B gene were introduced into Y1 adrenocortical tumor cells by cotransfection with pSV2-neo. Cells transfected with the 21-OHase A gene expressed 21-OHase as determined by steroid metabolism and by RNA blot hybridization; 21-OHase transcripts were not detected in parent Y1 cells or in cells transfected with the 21-OHase B gene. Treatment of 21-OHase A transfectants with adrenocorticotropin increased 21-OHase mRNA levels by up to 10-fold, thus mimicking the observed effect of this hormone on 21-OHase levels in primary adrenal cultures. The regulated expression of the 21-OHase A gene in transfected Y1 cells should provide a useful system for the investigation of factors controlling the adrenal-specific regulation of 21-OHase activity.

3 Beta-hydroxysteroid dehydrogenase-isomerase activity in bovine adrenocortical cells in culture: lack of response to ACTH treatment

Primary cultures of bovine adrenocortical cells (BAC) were used to determine whether the adrenal microsomal 3 beta-hydroxysteroid dehydrogenase-isomerase complex (3 beta-HSD), like the 17 alpha-hydroxylase (17-OHase), responded to ACTH treatment with an increase in activity. Both enzymes influence the steroidogenic path leading to 17 alpha-hydroxyprogesterone formation and thus could affect adrenal androgen biosynthesis. 3 beta-HSD Activity in postmitochondrial supernatant fluid, homogenates or cell monolayers remained unchanged after cells had been maintained in 1 microM ACTH up to 48 h. Since ACTH exposure led to a marked increase in 17-OHase activity over the same time period, it is concluded that, under the conditions used, the 3 beta-HSD-isomerase complex in BAC is nonresponsive to tropic hormone treatment.

Regulation of the biosynthesis of cytochromes P-450 involved in steroid hormone synthesis

The actions of ACTH to regulate the synthesis of the various enzymes involved in steroid hormone biosynthesis have been studied using bovine adrenocortical cells in monolayer culture. ACTH causes an increase in the synthesis of both the mitochondrial and the microsomal forms of cytochrome P-450 involved in steroid hormone biosynthesis, as well as of the iron-sulfur protein involved in transferring electrons to the mitochondrial forms of cytochrome P-450, namely, adrenodoxin. This increased synthesis is reflective of an increase in translatability of mRNA species specific for these various proteins, and appears in each case to be mediated by cyclic AMP. Whereas the mitochondrial proteins are synthesized as precursors of higher molecular weight which are processed upon insertion into the mitochondria, the microsomal proteins are synthesized as species identical in molecular weight to the mature forms. In order to determine whether the action of ACTH to increase the rate of synthesis of these proteins is the result of an increase in the levels of specific mRNA species, cDNA clones complementary to these mRNA species are being isolated. These probes will also make it possible to characterize the genes encoding the steroidogenic enzymes, as well as to identify regulatory elements which control their transcription.

The stimulation by ACTH of 17 alpha-hydroxylation in cultures or rabbit adrenal cells

Adrenal cells from control rabbits (control-cells) and from rabbits that had been injected twice daily for 3 days prior to sacrifice with 25 IU ACTH (ACTH-cells) were cultured both in the absence and presence of 100 mIU ACTH. Culture durations varied from 24 to 120 h in 24 h increments. The culture medium was changed daily and fresh ACTH added to appropriate vessels. At the time of the final media change 0.1 muCi [4-14C]pregnenolone was added. Twenty-four hours later the cultures were terminated and the products formed from the pregnenolone were isolated, quantified and identified by solvent extraction, chromatography and crystallization to constant specific activity. After 72 h ACTH-cells cultured in the presence of ACTH converted 18.5% of the pregnenolone substrate to 17-hydroxycorticosteroids (cortisol plus 11-deoxycortisol) while ACTH-cells cultured in the absence of ACTH converted a maximum of 1.6%. A similar but smaller difference, 10.9 vs 2.1%, was recorded with control cells cultured in the presence and absence of ACTH. Corticosterone production from [4-14C]pregnenolone in the 72-h cultures was increased to a lesser degree by ACTH exposure. In ACTH-cells the conversion climbed from 5.9 to 10.5% and from 9.6 to 12.0% in control cells. Microscopic examination of parallel cultures showed no significant differences in cell density between cells cultured in the presence or absence of ACTH. 17 alpha-Hydroxylase activity arising from the in vivo stimulation did not survive cell division in culture, but required the continual presence of ACTH. In conclusion, the data show that ACTH is capable of stimulating 17-hydroxycorticoid formation in rabbit adrenal cell cultures.

The enhancement of pregnenolone production as the main mechanism of the prolonged stimulatory effect of ACTH on cortisol production by guinea-pig adrenocortical cells

The prolonged stimulatory influence of corticotropin (ACTH) on the adrenocortical steroidogenic response to ACTH was studied in guinea-pig adrenocortical cells harvested from control and ACTH-treated animals (ACTH1-24, 50 micrograms s.c. twice daily on the day preceding the in vitro experiment). The maximal capacity to produce cortisol in response to ACTH (by 10(5) cells and 2 h incubation) was increased from 341.8 +/- 36.3 ng (control group) to 663.3 +/- 37.6 ng for cells obtained from guinea-pigs treated in vivo with ACTH. In the presence of trilostane, added to the cells in order to block the conversion of pregnenolone to cortisol, the net maximal output of pregnenolone and 17-hydroxypregnenolone in response to ACTH was significantly increased in adrenocortical cells from ACTH-treated animals (449.5 +/- 35.8 ng pregnenolone and 85.7 +/- 10.5 ng 17-hydroxypregnenolone vs 269.1 +/- 36.3 ng pregnenolone and 43.7 +/- 8.51 ng 17-hydroxypregnenolone for cells from control guinea-pigs). It appeared therefore that the total production of pregnenolone (as estimated by the sum of pregnenolone and 17-hydroxypregnenolone produced by the cells incubated with trilostane) nearly reached the level of the maximal production of cortisol in response to ACTH and was also significantly enhanced for cells from ACTH-treated animals (532.2 +/- 38.4 ng vs 312.8 +/- 40.0 ng for cells from control group). By contrast, no effect was documented on 17 alpha-hydroxylase activity since 17 alpha-hydroxylation index was similar for both types of adrenocortical cells (16.3 +/- 2.05% for ACTH-treated animals and 14.2 +/- 2.83% for control group). It was concluded therefore that the prolonged stimulatory influence of ACTH on pregnenolone production is the main mechanism of the enhancement of cortisol synthesis by guinea-pig adrenocortical cells previously stimulated by ACTH.

Identification of the cycloheximide-sensitive site in angiotensin-stimulated aldosterone synthesis

We have investigated the action of a protein synthesis inhibitor on the ability of angiotensin II (AII) to stimulate steroid synthesis. Isolated bovine adrenal glomerulosa cells were incubated in the presence and absence of angiotensin and cycloheximide, and the effects of the inhibitor on six cellular processes were measured. Cycloheximide at 7 and 28 microM inhibited the ability of the hormone to stimulate aldosterone synthesis. These concentrations of cycloheximide blocked protein synthesis by 72 and 79% respectively. Cycloheximide did not block receptor binding of angiotensin, the effect of angiotensin on [32P]phosphate incorporation into phosphatidylinositol, nor the ability of the hormone to alter 45Ca2+ fluxes. Mitochondrial conversion of cholesterol to pregnenolone is thought to be the rate-determining step in corticosteroid synthesis. Mitochondria isolated from cells treated with angiotensin made pregnenolone at a higher rate than control mitochondria. Cycloheximide blocked this effect when it was present in the cell incubation medium with angiotensin. Cycloheximide added directly to mitochondria had no effect on pregnenolone synthesis. Cycloheximide also blocked AII stimulation of pregnenolone synthesis in intact cells. We propose that protein synthesis is required for angiotensin to exert its stimulatory effects at one particular locus: activation of mitochondrial pregnenolone synthesis. Protein synthesis is not required for other angiotensin-stimulated processes in bovine adrenal glomerulosa cells.

The prolonged stimulatory effect of ACTH on 11 beta-hydroxylation, and its contribution to the steroidogenic potency of adrenocortical cells

The mechanism of the prolonged stimulatory influence of corticotropin (ACTH) on the capacity of adrenocortical cells to produce cortisol in response to ACTH and more specifically the role of 11 beta-hydroxylation, was studied on guinea-pig adrenocortical cells dispersed from control and ACTH-treated animals. As a result of the previous in vivo exposure to ACTH, the net maximal production of glucocorticoids in response to ACTH (by 10(5) cells and 2 h incubation) increased from 660 +/- 33.9 ng (control group) to 1105 +/- 117.9 ng for cells from ACTH-treated animals (P less than 0.001), whereas the apparent affinity of the steroidogenic response remained unchanged. In addition there occurred an increased conversion of exogenous pregnenolone into cortisol by cells from ACTH-treated animals, indicating a prolonged stimulatory influence of ACTH on the post-pregnenolone pathway of cortisol biosynthesis. The activity of 11 beta-hydroxylation step was therefore examined by incubating the adrenocortical cells from control and ACTH-treated animals in the presence of increasing amounts of 11-deoxycortisol. The maximal capacity of 11-deoxycortisol conversion into cortisol was increased as a result of the in vivo exposure to ACTH, averaging 3423 +/- 211 ng cortisol formed from 5 micrograms 11-deoxycortisol by 10(5) cells from ACTH-treated animals vs 2074 +/- 185 ng for cells from control guinea-pigs (P less than 0.001). However, the conversion of lower amounts of 11-deoxycortisol into cortisol, reproducing quantitatively the maximal effect of ACTH on cortisol biosynthesis, was only barely increased in cells from ACTH-treated animals (P greater than 0.05). Therefore it was concluded that ACTH increases in a lasting way not only the overall steroidogenic capacity of adrenocortical cells but also the maximal efficiency of 11 beta-hydroxylation. Since the latter effect cannot account quantitatively for the magnitude of the lasting effect of ACTH on the maximal capacity of adrenocortical cells to produce cortisol in response to ACTH, it appears that the prolonged influence of ACTH on cortisol biosynthesis should also involve a stimulatory influence of the peptide on earlier step(s) of steroidogenesis.

Lipoproteins and the regulation of adrenal steroidogenesis

ACTH has both short-term (acute) and long-term (chronic) effects to regulate steroid hormone biosynthesis in the adrenal cortex. The acute action of ACTH involves the mobilization of cholesterol and its binding to cytochrome P-450scc. The long-term action of ACTH involves the regulation of synthesis of the various enzymes involved in steroidogenesis. Evidence is presented that cholesterol may have a role to play in this regulatory process as it does in the short-term action of ACTH, consistent with the concept that substrates of specific forms of cytochrome P-450 are frequently able to regulate the synthesis of these specific forms.

The stimulatory effect of corticotropin on cortisol biosynthetic pathway in guinea-pig adrenocortical cells

The mechanism of the prolonged stimulatory effect of corticotropin (ACTH) on adrenocortical synthesis of cortisol was studied in guinea-pig adrenocortical cells harvested from control animals and from guinea-pigs submitted 24 h before the sacrifice to a prolonged ether anesthesia in an attempt to induce a release of endogenous ACTH. As a result of this in vivo exposure to endogenous ACTH, the maximal capacity to produce glucocorticoids (by 1 X 10(5) cells incubated during 2 h) in response to ACTH increased from 579 +/- 111 ng (control group) to 915 +/- 143 ng for cells from treated animals, whereas the apparent affinity of the steroidogenic response to ACTH remained unchanged. This hyper-reactivity of cells from anesthetized animals was also evident in the presence of dibutyryl cyclic AMP. Moreover, there was increased conversion of exogenous pregnenolone into cortisol by cells from previously anesthetized animals. It was therefore concluded that ACTH increases in a lasting way the activity of steroidogenic pathway leading to cortisol synthesis by adrenocortical cells at sites distal to cyclic AMP generation. Besides an obvious increase of formation of pregnenolone in response to ACTH, it seems that this ACTH-induced enhancement in the capacity of the steroidogenic response to ACTH also implies a prolonged stimulatory influence of the peptide on the post-pregnenolone steroidogenic pathway leading to cortisol synthesis.

Effects of ACTH on steroidogenesis in bovine adrenocortical cells in primary culture--increased secretion of 17 alpha-hydroxylated steroids associated with a refractoriness in total steroid output

The long-term effects of ACTH on steroidogenesis in bovine adrenocortical cells maintained in primary culture have been investigated. Cells in monolayer culture were incubated in the presence or absence of ACTH for up to 72 h, and the steroid content of the incubation medium was assayed at 12 h intervals. During the first 12 h, adrenocortical cells incubated in the presence of ACTH (10(-9) M and 10(-6) M) produced substantially more cortisol and corticosterone than did cells incubated in the absence of ACTH. The production of steroidogenic intermediates such as pregnenolone, progesterone, and 17 alpha-hydroxypregnenolone, as well as 17 alpha-hydroxyprogesterone, 11-deoxycortisol, and 11-deoxycorticosterone also was increased by short-term (12 h) treatment with ACTH. Thereafter, corticosteroid production by cells incubated in the continued presence of ACTH decreased in a time and concentration dependent fashion. The maximal rate of cortisol production by cells incubated in the presence of ACTH (10(-9) M and 10(-6) M) for 72 h was only one third that of cells incubated in the presence of ACTH for 12 h. More dramatically, by 36 h, corticosterone secretion by cells incubated in the presence of ACTH (10(-6) M) declined to less than 20% of that of nontreated cells, and the production of 11-deoxycorticosterone was no longer detectable. ACTH also induced refractoriness in the production of other C21-steroids (pregnenolone, progesterone, 17 alpha-hydroxypregnenolone, 17 alpha-hydroxyprogesterone, and 11-deoxycortisol) as well as of C19-steroids (dehydroepiandrosterone, androstenedione, and 11 beta-hydroxyandrostenedione). The ACTH-induced refractoriness in the production of C21-steroids lacking a 17 alpha-hydroxyl group occurred earlier than that of 17-hydroxylated C21-steroids. Despite the decline in total corticosteroid production, the long term effect of ACTH was to enhance the relative secretion of 17 alpha-hydroxylated steroids and C19-steroids. Adrenocortical cells incubated for 72 h in the presence of ACTH continued to secrete cortisol, 17 alpha-hydroxyprogesterone, 11-deoxycortisol, and 11 beta-hydroxyandrostenedione in increased amounts. In fact, 11-deoxycortisol became a major secretory product of the ACTH-refractory adrenocortical cell. These results are indicative that ACTH acts in diverse manners on the bovine adrenocortical cell to affect corticosteroid secretion. The initial stimulation of corticosteroid production appears to be reflective of an increase in overall substrate (cholesterol) utilization and probably is mediated, in part, by an increase in cholesterol side chain cleavage activity. The secretion of 17 alpha-hydroxysteroids and C19-steroids is enhanced further by an action of ACTH to increase 17 alpha-hydroxylase activity and possibly also 17,20-lyase activity. The ACTH-induced refractoriness in corticosteroid production, on the other hand, appears to result primarily from a decline in precursor (cholesterol) utilization.

Adrenocorticotropic hormone increases specific proteins of the mitochondrial fraction that are translated inside or outside this organelle in cultured adrenal tumor cells

In addition to its stimulatory effects on steroidogenesis, adrenocorticotropic hormone (ACTH) also has a trophic action on the adrenal cell. This is manifested in part by increases in the levels of key mitochondrial steroidogenic enzymes. The mechanism by which this trophic action of ACTH occurs has been studied in monolayer cultures of mouse adrenal cortical tumor cells. ACTH treatment of these cells stimulates the relative incorporation of amino acids into at least eight specific proteins in mitochondrial preparations. Two of these ACTH-responsive proteins are among the nine major adrenal polypeptides that fulfill the criteria of mitochondrial translation products: (i) their synthesis in intact cells is specifically resistant to inhibition by cycloheximide yet uniquely sensitive to chloramphenicol and (ii) they are synthesized in vitro by isolated mitochondria. The other six ACTH-responsive proteins are within the much larger category of mitochondrial proteins that are synthesized on cytoplasmic ribosomes. One of the proteins synthesized in the cytoplasm electrophoretically comigrates with purified beef adrenodoxin reductase and another with beef adrenodoxin. These findings indicate that ACTH regulates the synthesis (and turnover, or both) of specific mitochondrial proteins that are synthesized inside as well as outside the mitochondria of these adrenal cells.

Hormonal regulation of the adrenocortical cell

Monolayer cultures of bovine and human adrenocortical cells have been used to study regulation of growth and function. Homogeneous bovine adrenocortical cells exhibit a finite life span of approximately 60 generations in culture. Full maintenance of differentiated function (steroid hormone synthesis) requires an inducer such as ACTH and antioxidizing conditions. Full induction of differentiated function occurs only when cellular hypertrophy is stimulated by growth factors such as fibroblast growth factor and serum. ACTH and other agents that increase cellular cAMP inhibit replication but do not block growth factor-induced cellular hypertrophy. ACTH and growth factors together result in a hypertrophied, hyperfunctional cell. Replication ensues only when desensitization to the growth inhibitory effects of ACTH occurs. Cultures of the definitive and fetal zones of the human fetal adrenal cortex synthesize the steroids characteristic of the two zones in vivo. ACTH stimulates production of dehydroepiandrosterone (DHA), the major steroid product of the fetal zone, and of cortisol, the characteristic steroid product of the definitive zone. Prolonged ACTH treatment of fetal zone cultures results in a preferential increase in cortisol production so that the pattern of steroid synthesis becomes that of the definitive zone. The preferential increase in cortisol production by fetal Zone cultures results from induction of 3 beta-hydroxysteroid dehydrogenase, delta 4,5 isomerase activity, which is limiting in fetal zone cells. ACTH thus causes a phenotypic change in fetal zone cells to that of definitive zone cells. In both bovine and human adrenocortical cells, the principal effect of ACTH is to induce full expression of differentiated function. This occurs only under conditions where growth substances and nutrients permit full amplification.

The ultrastructure of functional mouse adrenal cortical tumor cells in vitro

Cells derived from a transplantable mouse adrenal cortical tumor maintain their differentiated function in vitro and secrete steroids in response to ACTH and other stimulatory agents. The cell line has been widely employed for various biochemical investigations but there have been few attempts to correlate this work with morphologic data. This communication describes the electron microscopic appearance of the tumor transplant in vivo and primary cultures derived from it at various intervals after the cells are placed in culture. Tumor cells in vivo bear considerable resemblance to normal adult mouse adrenal cortical cells. Organelles generally considered to be directly involved in steroid biosynthesis (mitochondria, smooth endoplasmic reticulum and lipid droplets) are not drastically altered. Certain modifications of the vasculature and cell membrane, seemingly related to steroidogenesis, are present in both the tumor and normal adrenal cortex. Within 2 days after the tumor cells are introduced to culture, their cytoplasm assumes a more simplified appearance. Smooth endoplasmic reticulum is less conspicuous and free ribosomes and polysomes are very abundant. Mitchondrial inner membranes are reorganized from a saccular arrangement in the cells in vivo into distinct lamellar cristae. The tumor cells now resemble undifferentiated embryonic adrenal cells, or cultured adrenal cells from various mammalian sources which have dedifferentiated in the absence of ACTH. In their morphologically unspecialized state, the normal cells are incapable of functional responses to ACTH. In contrast, the cultured, dedifferentiated tumor cells respond within minutes to this hormone and can demonstrate 5-20 fold increases in their basal steroid output. These data suggest that substantial steroidogenic activity can occur although the characteristic appearance of adrenal mitochondria is absent.

Hormonal regulation of initiation of DNA synthesis and of differentiated function in Y-1 adrenal cortical cells

ACTH, 8-Br-cAMP, and serum deprivation arrested Y-1 functional mouse adrenal tumor cells in the G1 phase of the cell cycle. Though ACTH and 8-Br-cAMP treated cells were larger with increased macromolecular synthetic rates compared to cells arrested in G1 by serum removal, a similar 8- to 10-hours lag to initiation of DNA synthesis was observed after either ACTH or 8-Br-cAMP removal or after serum addition. After the 8- to 10-hour lag period, cells entered S phase exponentially. ACTH or 8-Br-cAMP opposed serum induced DNA synthesis initiation only when added prior to S. Once commitment to DNA synthesis occurred, ACTH or 8-Br-cAMP addition did not inhibit DNA synthesis although 8-Br-cAMP induced a secondary block in G2. Though ACTH and 8-Br-cAMP inhibited serum induced initiation of DNA synthesis and did not affect serum induced cellular hypertrophy, both substances increased the steroidogenic capacity of the cell. ACTH and 8-Br-cAMP thus appear to specifically oppose the stimulatory effects of serum on initiation of DNA synthesis while inducing the differentiated function of the cell.

Characteristics of the response of human adrenocortical cells to ACTH

The effects of adrenocorticotrophic hormone (ACTH) on human adrenocortical steroidogenesis were studied in adrenocortical cells which had been isolated from normal and hyperplastic glands by a technique combining tyrpsin digestion and mechanical dispersion, and incubated in the presence of ACTH or dibutyryl cyclic AMP (dbcAMP). The response was measured in terms of cyclic AMP, cortisol, corticosterone, 11-deoxycortisol and cortisone production. A classical sigmoid curve, calculated by non-linear, least square method, related the increase in cAMP production or in steroidogenesis to the log dose of ACTH. For the normal adrenocortical cells, the estimated concentration of ACTH inducing a half-maximal response was approximated 2h0 pg ACTH 1-24/ml for steroidogenesis, against 437 pg/ml for cAMP production. The estimated Vmax (per 107 cells/ml, on average) was 27 pmol cAMP/2 and for steroidogenesis (in ng/2 h): 188 for cortisol, 106 for corticosterone, 37 for 11-deoxycortisol, and 32 for cortisone, dbcAMP (1.0 mM) stimulated steroidogenesis to a comparable extent. The cells from a hyperplastic adrenal gland exhibited a steroidogenic response to ACTH and dbcAMP which was 2-3 times greater than the response of a similar number of normal adrenocortical cells. Calculated per pmol cAMP generated, the ACTH-stimulated cortisol production by cells from hyperplastic gland was also increased with respect to normal cell response. These data suggest a prolonged effect of ACTH on cortisol biosynthetic pathway beyond the membrane step of cAMP generation.

The effect of hydrocortisone and adrenocorticotrophic hormone on monoamine oxidase and tyrosine hydroxylase in explant cultures of embryonic chick sympathetic ganglia

Sympathetic ganglia from 13- to 15-day-old embryonic chicks were cultured for up to 2 days in Leighton tubes. The influence of hydrocortisone and ACTH added to the culture medium on the enzymes monoamine oxidase (MAO) and tyrosine hydroxylase was studied. Hydrocortisone (5 times 10(-5)M) had no effect on tyrosine hydroxylase but increased MAO activity by up to 46 percent over control values under conditions of low or zero nerve growth factor (NGF) concentration. ACTH also increased ganglionic MAO activity, the effect again depending on NGF concentration. This time the maximal response (an increase of 50 percent over controls) was seen at high NGF concentrations. This response was similar to the effect of 1 mM dibutyryl cyclic AMP, and was blocked by 1 times 10-5 M propranolol and 10 muM prostaglandin E(1). ACTH only slightly increased tyrosine hydroxylase activity and this effect was due to a small (18 percent) increase in sympathetic neurone number. Guanosine 5-diphosphate (0.5 mM) was found to increase tyrosine hydroxylase activity by 57 percent and this effect was blocked by the presence of ACTH.