Dibutyryl Cyclic Adenosine 3′,5′-monophosphate Research Articles

Acetylcholine as pruritugenic mediator

To explore the mechanisms of the effects of sucralfate on the stomach, we investigated the action of sucrose octasulfate (SOS), a constituent of sucralfate, on the function of canine gastric parietal cells and somatostatin cells and in the isolated perfused intact rat stomach. Somatostatin cells from the canine gastric fundus were isolated by EDTA-collagenase dispersion and counterflow elutriation, and somatostatin-like immunoreactivity (SLI) release in response to SOS was measured by radioimmunoassay. Similar methods were used to isolate gastric parietal cells, in which gastric acid secretion was measured by uptake of a radiolabeled weak base, [14C]aminopyrine. SLI release by the intact rat stomach was examined in an isolated vascularly perfused rat stomach model. SOS, either alone or co-administered with epinephrine or gastrin heptadecapeptide (G17), dose-dependently stimulated SLI release by isolated canine fundic D-cells. At the highest doses, SOS potentiated the effect of epinephrine but not G17. Similarly, SOS potentiated the stimulating effect of dibutyryl cyclic adenosine 3′,5′-monophosphate (DBcAMP), but not 12-O-tetradecanoylphorbol 13-acetate (TPA). The effect of SOS on SLI release could be inhibited by octreotide, a somatostatin analogue. SOS did not alter acid secretion by cultured canine parietal cells either in the basal state or when coadministered with acid secretagogues. In isolated perfused rat stomach studies, SOS produced a significant (60% greater than basal) increase in SLI secretion. There was a similar effect when SOS was perfused against a background of isoproterenol. SOS stimulates SLI release from gastric somatostatin cells and from the isolated perfused stomach but has no direct effect on gastric parietal cells. These actions of SOS may mediate in part the apparent ability of sucralfate to enhance gastric mucosal defense.

Sucrose octasulfate stimulates gastric somatostatin release

To explore the mechanisms of the effects of sucralfate on the stomach, we investigated the action of sucrose octasulfate (SOS), a constituent of sucralfate, on the function of canine gastric parietal cells and somatostatin cells and in the isolated perfused intact rat stomach. Somatostatin cells from the canine gastric fundus were isolated by EDTA-collagenase dispersion and counterflow elutriation, and somatostatin-like immunoreactivity (SLI) release in response to SOS was measured by radioimmunoassay. Similar methods were used to isolate gastric parietal cells, in which gastric acid secretion was measured by uptake of a radiolabeled weak base, [ 14C]aminopyrine. SLI release by the intact rat stomach was examined in an isolated vascularly perfused rat stomach model. SOS, either alone or co-administered with epinephrine or gastrin heptadecapeptide (G17), dose-dependently stimulated SLI release by isolated canine fundic D-cells. At the highest doses, SOS potentiated the effect of epinephrine but not G17. Similarly, SOS potentiated the stimulating effect of dibutyryl cyclic adenosine 3′,5′-monophosphate (DBcAMP), but not 12- O-tetradecanoylphorbol 13-acetate (TPA). The effect of SOS on SLI release could be inhibited by octreotide, a somatostatin analogue. SOS did not alter acid secretion by cultured canine parietal cells either in the basal state or when coadministered with acid secretagogues. In isolated perfused rat stomach studies, SOS produced a significant (60% greater than basal) increase in SLI secretion. There was a similar effect when SOS was perfused against a background of isoproterenol. SOS stimulates SLI release from gastric somatostatin cells and from the isolated perfused stomach but has no direct effect on gastric parietal cells. These actions of SOS may mediate in part the apparent ability of sucralfate to enhance gastric mucosal defense.

The effect of ovine trophoblast protein-one on endometrial protein secretion and cyclic nucleotides.

The effect of ovine trophoblast protein-one (oTP-1) on endometrial protein secretion was examined by using a dual radioisotope technique in which 3H- and 35S-methionine were employed to measure relative rates of protein release into the medium by endometrial explant cultures (Exp. I). Endometrium (200 mg) from Day (D) 12 of the cycle was cultured with either 5 micrograms/ml oTP-1, 5 micrograms/ml bovine serum albumin (BSA) or 1 mM dibutyryl cyclic adenosine 3',5'-monophosphate (DbcAMP). Culture media from control BSA and treated explant cultures were mixed. Proteins were separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and detected by fluorography. Individual protein spots were punched from gels, extracted, and their radioactive content measured. Ratios of 3H:35S were used to determine treatment effects. In Experiment II, 3H- and 14C-leucine were used for the dual radiolabel, and the DbcAMP treatment was omitted. In both experiments, a protein having a molecular weight (Mr) of about 70,000 and a pI approximately equal to 4 was increased (p less than 0.01) 200-400% by oTP-1. Secretion of several other endometrial proteins was also amplified in the presence of oTP-1. The polypeptides that increased in response to oTP-1 were inhibited by DbcAMP, and vica versa. In Experiment III, endometrial explants from D12 cyclic ewes were cultured for 4 h with either 5 micrograms/ml oTP-1 or 5 micrograms/ml BSA to determine whether oTP-1 influenced concentrations of 3',5'-cyclic adenosine monophosphate (cAMP) and 3',5'-cyclic guanosine monophosphate (cGMP). Concentrations of cAMP in oTP-1-treated endometrium were lower (p less than 0.1) than in BSA-treated endometrium (0.29 vs. 0.41 pmoles/mg tissue, respectively). Levels of cGMP were unaffected by oTP-1. In Experiment IV, endometrium from D14 of the cycle was incubated in medium alone or in medium containing either 2 micrograms/ml oTP-1, 1 microgram/ml oxytocin (OXY), or oTP-1-plus-OXY. None of the treatments significantly affected cAMP levels. In Experiment V, D16 endometrium was collected from pregnant and nonpregnant ewes that had received either 0 or 10 IU OXY i.v. cAMP was higher (p less than 0.01) in endometrium from pregnant ewes compared to nonpregnant ewes (27.9 vs. 13.0 pmoles/mg tissue, respectively), but OXY had no detectable effect on endometrial content of cAMP in either nonpregnant or pregnant ewes.(ABSTRACT TRUNCATED AT 400 WORDS)

Mutagenicity studies with N6, O2′-dibutyryl cyclic adenosine 3′,5′-monophosphate (DBcAMP)

N 6, O 2′-Dibutyryl cyclic adenosine 3,5-monophosphate (DBcAMP) was studied for mutagenicity using the rec assay, the Ames method, and in vitro cytogenetics. DBcAMP had no mutagenic effect on B. subtilis in the rec assay, or on S. typhimurium (TA1535, TA1537, TA1538, TA98 and TA100) or E. coli (WP2 uvrA). In the cytogenetic study, a significant increase in chromosomal aberrations was observed at a concentration of 50 000 μg/ml, but it was considered that this effect could be attributed to the secondary effect of the high osmotic pressure in the culture medium. These results suggest that DBcAMP has no mutagenic potential.

Effects of adenosine on glucuronidation and uridine diphosphate glucuronic acid (UDPGA) synthesis in isolated rat hepatocytes

Dibutyryl cyclic adenosine 3':5'-monophosphate (DBcAMP) has been shown to inhibit glucuronidation of p-nitrophenol in a concentration-dependent manner in isolated rat hepatocytes. Adenosine (ADO) also decreased glucuronidation in a similar fashion. The effects of adenosine were examined on the variables controlling glucuronidation in intact cells. The addition of adenosine was without effect on either glucuronyltransferase or β-glucuronidase. Adenosine decreased undine diphosphate glucuronic acid (UDPGA) levels by 62% and, subsequently, inhibited glucuronidation by 41% in isolated rat hepatocytes. Since the synthesis of UDPGA requires NAD + for the dehydrogenation of UDP-glucose, alterations in the redox state could account for the decrease in intracellular UDPGA levels. The effects of ADO (500 μM) on lactate and pyruvate content and redox state were examined in rat hepatocytes. ADO caused a 2.1-fold increase in lactate levels and a 2.65-fold increase in the [lactate]/ [pyruvate] ratio. The NAD +/NADP ratio, therefore, was decreased by 63% in the presence of ADO. Carbohydrate reserve also affects UDPGA levels; thus, graded concentrations of glucose (5.5, 25, and 50 mM) were added to cells incubated with ADO. At 5.5 mM glucose, ADO caused a 61% decrease in glucuronide formation, while at concentrations of 25 and 50 mM glucose, the inhibition was diminished by 53 and 47% respectively. ADO appears to have decreased the synthesis of UDPGA by decreasing the NAD +/NADH ratio, thus inhibiting UDP-glucose dehydrogenase. Carbohydrate reserve also appears to be involved in the inhibition of glucuronidation mediated by ADO.

Inhibitory effect of cyclic adenosine-3′,5′-monophosphate on the induction of aryl hydrocarbon hydroxylase in the liver of female rats

The effect of dibutyryl cyclic adenosine-3′,5′-monophosphate (DBcAMP) on the activity of aryl hydrocarbon hydroxylase (AHH) was studied under in vivo conditions in the liver of female rats. To maintain an elevated level of DBcAMP for a longer period of time, the nucleotide was given by a continuous infusion up to 26 hr without disturbing the animals. Under these conditions the basal activity of AHH was not significantly changed, indicating that cAMP is not an inducer or inhibitor of AHH. On the other hand, 3-methylcholanthrene-and phenobarbital-mediated induction of AHH was reduced in the presence of DBcAMP by about 50 and 35%, respectively. A reduced induction rate of AHH has also been seen after the application of the herbicide atrazine, which increases the endogenous level of cAMP. The results suggest that cAMP is not involved in the induction of AHH caused by xenobiotics. The inhibitory effect of DBcAMP on the induction of AHH may be due to an inhibition of enzyme synthesis which, in turn, may be the consequence of a direct effect of DBcAMP or an indirect effect caused by changes in the level of steroid hormones.

Arrest of mammary tumor growth [formula omitted] by L-arginine: Stimulation of NAD-dependent activation of adenylate cyclase

In vivo growth of hormone-dependent rat mammary tumors was arrested by daily injections of L-arginine (L-arginine·HCl 50 mg/200g rat s.c.). Arginine + N 6,O 2′-dibutyryl cyclic adenosine 3′,5′-monophosphate (DBcAMP) acted synergistically to enhance the growth inhibitory effect. Growth arrest by arginine was accompanied by a sharp increase in cellular cAMP content, which was preceded by parallel increases in NAD-dependent ADP-ribosylation of the membrane proteins and NAD-dependent activation of adenylate cyclase. The ADP-ribosylation of the membrane proteins required GTP and was catalyzed similarly by the 105,000 × g supernatant fraction of the tumor and by cholera toxin. These results suggest a specific role for arginine in the cAMP-mediated inhibition of mammary tumors.

Dibutyryl cyclic-AMP mimics the effect of ovariectomy on a dehydrogenase in hormone-dependent mammary tumors

Growth of 7,12-dimethylbenz(α)anthracene(DMBA)-induced mammary carcinoma is arrested by either ovariectomy or treatment with N 6,0 2′ dibutyryl cyclic adenosine 3′, 5′-monophosphate (DBcAMP). When this occurs, a change in the isozyme pattern of glucose- 6-phosphate dehydrogenase (G 6PD) is observed. In growing tumors, 4 major molecular forms of glucose- 6-phosphate dehydrogenase (G 6PD), designated G 6PD- 1, - 2, - 3 and - 4, have been identified by their distinct electrophoretic mobilities, subcellular localizations, and substrate and cofactor specificities. In regressing tumors, due to either ovariectomy or DBcAMP treatment, G 6PD- 3 (microsome-associated) activity disappears. This activity reappears when tumor growth is resumed by either the injection of estradiol-valerate or cessation of DBcAMP treatment. A change in G 6PD- 3 activity does not occur in those DMBA tumors that continue to grow, rather than regress, after ovariectomy or DBcAMP treatment. G 6PD- 1 and - 2 (post microsomal supernatant-associated) activities decrease only during ovariectomy-induced tumor regression and G 6PD- 4 (mitochondria-associated) activity remains inaltered during DMBA tumor regression. The disappearance of G 6PD- 3 activity appears to be a common biochemical parameter found in the regression of a hormone-dependent mammary carcinoma following either ovariectomy or DBcAMP treatment of the host.

THE EFFECT OF CALCIUM AND DIBUTYRYL-cAMP ON THE SECRETION OF PARATHYROID HORMONE BY HUMAN PARATHYROID ADENOMAS IN ORGAN CULTURE

The effect of different calcium concentrations as well as dibutyryl-cyclic adenosine 3',5'-monophosphate (DB-cAMP) on the secretion of parathyroid hormone by human parathyroid adenomas taken from patients with primary hyperparathyroidism (pHPT) was studied in organ culture. Their influence on the release of hormone was determined. The tissue was incubated in culture medium for 4 h; the medium was changed hourly and analyzed for immunoreactive parathyroid hormone (PTH) by radioimmunoassay. The hormone secretion showed an inverse relationship to different calcium concentrations in the medium and could be stimulated independently of the calcium concentration by adding DB-cAMP. These results suggest that the examined parathyroid adenomas are sensitive to physiological stimuli.

Decreased estrogen binding in hormone-dependent mammary carcinoma following ovariectomy or dibutyryl cyclic amp treatment

Summary 7,12-Dimethylbenz( α )anthracene (DMBA)-induced mammary carcinomas regress after ovariectomy of the host or stop growing after treatment with N 6 , O 2 ′-dibutyryl-cyclic adenosine 3′,5′-monophosphate (DBcAMP). Six days after either treatment, estrogen binding of the tumor cytosol decreases to 50% of the growing control tumor cytosols. Neither the sedimentation profiles of the binding components seen on sucrose gradients nor the apparent binding affinity to estrogen ( K d ) is changed with the decrease of estrogen binding produced by either ovariectomy or DBcAMP treatment. These findings suggest that DBcAMP treatment mimics estrogen deprivation in the growth control of a hormone-dependent mammary tumor.

The role of cAMP on neoplastic cell growth and regression. III. Altered cAMP-binding in DBcAMP-unresponsive walker 256 mammary carcinoma

An exogenous supply of N 6,O 2′-dibutyryl cyclic adenosine 3′,5′-monophosphate (DBcAMP) in vivo produces regression of one type of Walker 256 mammary carcinoma cell population (DBcAMP-responsive); a second type of cell population continues to grow despite DBcAMP treatment (DBcAMP-unresponsive). A correlation was found between altered cAMP-binding of the tumor cytosol and DBcAMP-unresponsiveness. It was found that there was: a) a higher apparent dissociation constant (Kd) for cAMP-binding in unresponsive tumor cytosol in vitro , and b) unsaturability of cAMP-binding by unresponsive tumor cytosol in response to elevated cAMP levels in vivo . Cycloheximide abolished the saturation of cAMP binding in vivo as well as tumor regression produced by DBcAMP.

Induction of phosphoenolpyruvate carboxykinase and tyrosine aminotransferase in the isolated perfused rat liver: Interaction of dexamethasone and dibutyryl cyclic AMP

Recently we have found [l] that injection of N6, 02’-dibutyryl cyclic adenosine 3’,5’-monophosphate (DBcAMP) into adrenalectomized rats initially stimulated hepatic phosphoenolpyruvate carboxykinase (PEP-CK, EC 4.1.1.32) and tyrosine aminotransferase (TAT, EC 2.6.1.5) to the same degree as in intact rats. However, despite of repeated DBcAMP administration the raise in the activity of both enzymes ceased after 2 hr, but could be restored when hydrocortisone had been given at zero time. These results suggested that the maintenance of CAMP-mediated induction of PEP-CK and TAT is dependent on the simultaneous presence of glucocorticoids. Because of the obvious complications associated with whole animal experiments the hypothesis was now re-examined in the isolated perfused rat liver. It could be demonstrated that the interaction between CAMP and glucocorticoids, in fact, occurred as the result of direct participation of the administered agents at the tissue level. Moreover, our in vitro findings support the hypothesis derived from previous in viva studies [ 11, that CAMP elevates PEP-CK and TAT by a mechanism which, in principle, works independently from glucocorticoids while glucocorticoids stimulate a different process that is required for the maintenance of CAMP-mediated enzyme induction. 2. Materials and methods

Comparative effects of adenosine and adenine and guanine nucleotides on drug biotransformation in rats

The effect of various nucleotides and adenosine on the hepatic biotransformation of hexobarbital sodium (HB) and p-chloro-N-methylaniline (PCMA) was determined in male rats. Intraperitoneal administration of dibutyryl cyclic adenosine 3',5'-monophosphate (DBcAMP), alone and in combination with theophylline, and the cyclic adenosine 3',5'-monophosphate (cAMP)-theophylline combination prolonged HB sleeping time by more than 70%. cAMP or dibutyryl cyclic guanosine 3',5'-monophosphate (DBcGMP), alone or in combination with theophylline, failed to significantly alter the duration of HB-induced hypnosis. Plasma levels of HB upon awakening suggested that the increase in sleeping time was apparently not due to an altered sensitivity of the brain to the barbiturate. The effect appears to be related to an impairment of HB metabolism since only those compounds that inhibited HB oxidation when added to liver slices prolonged hypnosis. In addition, 5'-AMP, adenosine, and cyclic guanosine 3',5'-monophosphate (cGMP) failed to alter HB biotransformation by liver slices. A similar pattern of impairment of metabolism by liver slices was observed when PCMA was used as the substrate. The inhibitory effect of DBcAMP was not altered by concurrent addition of either cGMP or DBcGMP. No impairment in the rate of microsomal PCMA biotransformation resulted from addition of adenosine or any of the nucleotides used in this study.

The role of cyclic AMP in neoplastic cell growth and regression II. Growth arrest and glucose-6-phosphate dehydrogenase isozyme shift by dibutyryl cyclic AMP

N 6,O 2′-Dibutyryl cyclic adenosine 3′,5′-monophosphate (DBcAMP) injected into rats bearing MTW9 mammary carcinoma resulted in an early disappearance of tumor microsomal glucose-6-phosphate dehydrogenase activity while mitochondrial and supernatant isozyme activities were not affected. Prolonged DBcAMP treatment of rats bearing 5123 hepatoma significantly decreased all glucose-6-phosphate dehydrogenase isozyme activities but did not alter host liver isozyme activities or liver regeneration. Since DBcAMP treatment arrested growth of these tumors, the loss of microsomal glucose-6-phosphate dehydrogenase may be an early event in the inhibition of tumor growth in vivo .

Paradoxical response of plasma cortisol to pulse intravenous injection of synthetic corticotrophin and dibutyryl cyclic adenosine 3',5'-monophosphate in adult panhypopituitarism.

ABSTRACT 250 μg of synthetic β-1-24 corticotrophin and 10 mg/kg of dibutyryl cyclic adenosine 3′,5′-monophosphate (Db-cAMP) were iv pulse injected into six patients with adult panhypopituitarism. The plasma cortisol levels were determined as 11-OHCS at zero time and then at 2.5, 5, 7.5, 10, 15, 30, 60 and 180 min after the injection. The data were compared with those obtained under the same experimental conditions in groups of normal subjects. A paradoxical pattern of early plasma cortisol response after the two stimuli was found in the case of hypopituitarism in comparison with that observed in normal subjects, that is a higher response after Db-cAMP than after corticotrophin. This was dependent on a selective impairment of adrenal steroidogenic response to iv injection of corticotrophin, whereas the response to iv injection of Db-cAMP was normal. Moreover in hypopituitaric patients the time course of cortisol response after ACTH was clearly different from the normal. The plasma 11-OHCS levels never showed an early peak followed by a fall and a second subsequent rise but rose progressively after the injection to a plateau between 15 and 180 min. By contrast, after Db-cAMP the time course of the response was also similar to that observed in normal subjects. It is suggested that after chronic failure of ACTH the reduced cortisol response to iv acute administration of corticotrophin may also depend on a defect localized before the synthesis of intracellular cyclic AMP, i. e. in the binding between ACTH and the specific cell membrane bound receptor and/or in the inactivation of the membrane associated adenyl cyclase.

The behavioral effects of dibutyryl cyclic AMP in mice

Dibutyryl cyclic adenosine 3′,5′-monophosphate (DBcAMP), 25 mg/kg, administered intraperitoneally 25 minutes prior to testing produced a significant decrease in spontaneous locomotor activity (SLMA) to 58 percent of control and in exploratory behavior to 64 percent of control but failed to alter rotarod performance of mice. DBcAMP did not decrease activity when mice were pretreated with the nucleotide 24 hours prior to its subsequent administration. The results of time-response studies of DBcAMP and SLMA showed that the effects were present as early as 2 minutes after administration and persisted for approximately 90 minutes. Dose-response experiments showed a significant decrease in SLMA with 10 mg/kg and an 86 percent decrease with 75 mg/kg. The results suggest that DBcAMP acts centrally to alter several behavioral patterns in mice and that tolerance rapidly develops to its effects.

Early variations of plasma cortisol after pulse intravenous injection of dibutyryl cyclic adenosine 3',5'-monophosphate in normal subjects.

ABSTRACT 10 mg/kg of dibutyryl cyclic adenosine 3′,5′-monophosphate (Db-cAMP) was iv pulse injected into twelve healthy adult women. The plasma cortisol levels were determined as 11-OHCS at zero time and then at 2.5, 5, 7.5, 10, 15, 30, 60 and 180 min after the injection. The data were compared with those obtained at the corresponding times in two groups of eleven and seventeen healthy women after the injection of 250 ng and 250 μg of synthetic β-1-24 corticotrophin performed in the same manner as the injection of the nucleotide. The mean increments in plasma cortisol were significantly lower after Db-cAMP than after ACTH. Differences were noted by analyzing the time course of the responses. In the case of stimulation with Db-cAMP the 11-OHCS levels rose progressively to a maximum at 15–30 min. By contrast, a peak of plasma cortisol was evident in most cases within a few min after the injection of ACTH; after a fall, a later rise was then observed starting from 15 min. The differences in the plasma 11-OHCS responses after the two stimuli may also be of interest clinically for the investigation of some aspects of adrenal steroidogenesis.

Dietary and hormonal regulation of hepatic biosynthetic and catabolic enzymes of serine metabolism in rats.

The changes in the hepatic levels of activity of 3-P-glycerate dehydrogenase, D-glycerate dehydrogenase, L-serine: pyruvate transaminase and L-serine dehydratase have been determined in rats under varying conditions promoting either gluconeogenesis or amino acid biosynthesis. In the gluconeogenic states brought about by fasting, by administration of either cortisone, glucagon, or N6,O2′-dibutyryl cyclic adenosine-3′,5′-monophosphate (DBcAMP), and by alloxan diabetes, serine dehydratase activity was elevated. In the latter condition, insulin was effective in reducing the elevated level of activity. The level of serine: pyruvate transaminase activity was also increased by all of the above conditions except fasting, although the magnitude of the response and the time required to elicit a change varied from those observed for serine dehydratase. The glucagonmediated elevation of the levels of activity of both enzymes occurred independently of glucocorticoids. The level of activity of D-glycerate dehydrogenase...

Regulation of Phosphoenolpyruvate Carboxykinase and Tyrosine Transaminase in Hepatoma Cell Cultures: I. EFFECTS OF GLUCOCORTICOIDS, N6,O2′-DIBUTYRYL CYCLIC ADENOSINE 3′,5′-MONOPHOSPHATE AND INSULIN IN REUBER H35 CELLS

Abstract Reuber H35 hepatoma cells growing in monolayer cultures have been found to contain the soluble enzyme phosphoenolpyruvate carboxykinase. The activity of this enzyme can be increased 2- to 3-fold by the addition of either N6,O2'-dibutyryl cyclic adenosine 3',5'-monophosphate (DBcAMP) or the synthetic glucocorticoid dexamethasone (Δ1,2,9α-fluoro,16α-methyl cortisol). Tyrosine transaminase responds similarly to DBcAMP but its activity was elevated 5- to 8-fold by dexamethasone. The effects of each inducer on both enzymes were similar with respect to kinetics, dose-response relationships, analogues, and cycloheximide inhibition. The response of both enzymes to DBcAMP, however, was more rapid than to dexamethasone. The rate of transaminase synthesis was increased 2- to 3-fold by DBcAMP but no effect of the cyclic nucleotide could be detected on the rate of transaminase degradation. Elevation of carboxykinase activity appears to be due to an increase in the rate of synthesis of this enzyme based on immunological evidence and cycloheximide inhibition of the response to both dexamethasone and DBcAMP. Insulin completely suppressed the effects of both DBcAMP and dexamethasone on the carboxykinase at the same time that it produced additive increases in transaminase activity with these agents. On the other hand, progesterone completely prevented the effects of dexamethasone on both enzymes but did not inhibit the effects of DBcAMP on either enzyme.

Isolated adrenal cells: corticosterone production in response to cyclic AMP (adenosine-3',5'-monophosphate).

SummaryCyclic AMP and dibutyryl cyclic AMP stimulate corticosterone production when added to suspensions of isolated rat adrenal cells. Theophylline enhances the action of cyclic AMP but not that of ACTH. Adenosine, 5′-AMP, and ATP exhibit no or very slight steroidogenic activity in the isolated cell system.