Effects of adenosine 5'-monophosphate and adenosine 3',5'-cyclic monophosphate on l cells.

The adenine nucleotides, 5'-AMP and 3',5'-cyclic AMP block L cells in the S-phase of the cell cycle. The intracellular level of cyclic AMP is reduced after incubation of cells with 5'-AMP, and rates of uridine transport are increased after incubation with either 5'-AMP or cyclic AMP. On the contrary, cyclic AMP levels are increased and uridine transport decreased in cells treated with an inhibitor of the cyclic AMP phosphodiesterase. This inhibitor partially reverses the growth-inhibitory effect of cyclic AMP, indicating that a breakdown product is the effective inhibitor of growth. The inhibition of cell growth induced by the adenine nucleotides is prevented by uridine, suggesting that the block in S is due to a lack of availability of pyrimidines.     

Differences and similarities between guanosine 3',5'-cyclic monophosphate phosphodiesterase and adenosine 3',5'-cyclic monophosphate phosphodiesterase activities in neuroblastoma cells in culture.

There are phosphodiesterase activities in both particulate and supernatant fractions which hydrolyze guanosine 3',5'-cyclic monophosphate (cGMP) and adenosine 3',5'-cyclic monophosphate (cAMP) with an apparent Km of 2-8 muM and with an apparent Km of 44-222 muM. 4-(3-Butoxy-4-methoxybenzyl-2-imidazolidinone (RO20-1724) did not inhibit cGMP phosphodiesterase activity in homogenates of mouse neuroblastoma cells, but markedly inhibited cAMP phosphodiesterase activity. Papaverine and theophylline inhibited both cGMP and cAMP phosphodiesterase activities to about the same extent. The former was more potent than the latter. The specific activity of cGMP phosphodiesterase as a function of protein concentrations first increased and then decreased. The specific activity of cAMP phosphodiesterase decreased under a similar experimental condition.     

Effect of glucose on the fruiting body formation and adenosine 3',5'-cyclic monophosphate levels in Coprinus macrorhizus

The formation of fruiting bodies in the monokaryotic fis(c) strain and a dikaryon of Coprinus macrorhizus was inhibited by growth in high-glucose media. In high-glucose media the characteristic burst of adenosine 3',5'-cyclic monophosphate (cAMP) accumulation during fruiting-body formation was absent. Enzymatic activity assays revealed that mycelia grown in high-glucose media contained relatively lower amounts of adenylate cyclase and cAMP-phosphodiesterase than mycelia grown in low-glucose media. The synthesis of inducible d-serine deaminase and tryptophanase was repressed in high-glucose media. A mutant (gluR) in which the glucose repression of fruiting-body formation is affected was isolated by selection in high-glucose media. The mutation caused the cAMP levels to be no longer affected by glucose and affected ability to synthesize the inducible d-serine deaminase and tryptophanase. The gluR mutant was partially dominant in dikaryons. It is suggested that cAMP may play important roles in inducing fruiting bodies and in controlling inducible enzyme synthesis in C. macrorhizus.     

Hydrolysis of 2',3'-cyclic adenosine monophosphate and 3',5'-cyclic adenosine monophosphate in subcellular fractions of normal and neoplastic mouse spleen

A comparison has been made between the capacity to hydrolyse 2′,3′-cyclic adenosine monophosphate and 3′,5′-cyclic adenosine monophosphate in subcellular fractions of normal and neoplastic (lymphosarcoma) spleen of C₅₇BL mice. The effect of X-irradiation on these activities was tested. Subcellular fractionation of normal and lymphosarcoma spleen points to a different overall localization of the enzymes. The 2′,3′-cyclic nucleotide phosphodiesterase (2′,3′-cAMPase) has its highest specific activity in the particulate fractions of the cell, while the data on 3′,5′-cyclic nucleotide phosphodiesterase (3′,5′-cAMPase) show the highest activity in the soluble fraction. The 2′,3′-cAMPase activity is higher in the tumor as compared to the normal tissue, while the opposite holds for 3′,5′-cAMPase. Total body irradiation of normal mice with a dose of 600 rads of X-rays, results in a clear drop in 2′,3′-cAMPase 48 hours after the exposure. The 3′,5′-cAMPase is hardly affected at this time. Neither imidazol nor Mg⁺⁺ has any influence on the 2′,3′-cAMPase. The pH optimum for 3′,5′-cAMPase and 2′,3′-cAMPase appears to be 7.7 and 6.2 respectively. This report suggests a no-identity of the two enzymes in mouse spleen, a situation different from that found in certain plants.     

Circadian variations in plasma 3':5'-cyclic adenosine monophosphate and 3':5'-cyclic guanosine monophosphate of normal adults.

Circadian variations in plasma cyclic AMP and cyclic GMP were studied in thirteen male subjects (20–22 years old) under controlled invironmental condition. Plasma collections were made every six hours. Cyclic AMP and cyclic GMP were determined by radioimmunoassay. Individual values of plasma cyclic AMP at 0800 are between 13.0 and 25.8 pmole/ml, and cyclic GMP between 2.5 and 7.0 pmole/ml. Cyclic AMP demonstrated the circadian variation with the maximum level at 1400 and the minimum at 0200, and cyclic GMP with the highest level at 1400 and the lowest level at 0800.     

The effect of p,p'-dichlorodiphenyltrichloroethane on levels of guanosine 3',5'-cyclic monophosphate and adenosine 3',5'-cyclic monophosphate in two species of insects.

Within 1 h after topical application of a convulsive dose (4 mug per fly, 47 mg/kg) of p,p'-dichlorodiphenyltrichloroethane (DDT) to the adult male of Sarcophaga bullata Parker, guanosine 3',5'-cyclic monophosphate (cyclic GMP) levels rose by 71.5% (P less than 0.05) in the head, 159.5% (P less than 0.01) in the thorax, and 23.4% (P greater than 0.05) in the abdomen compared to controls. Adenosine 3',5'-cyclic monophosphate (cyclic AMP) levels were not significantly affected by the DDT treatment. A convulsive dose (100 mug per larva, 250 mg/kg) of DDT applied to larvae of Mamestra configurata Wlk. caused the whole body level of cyclic GMP to rise by 81.6% (P less than 0.01) after 1 h, and by 95.9% (P less than 0.01) after 3 h. Levels of cyclic AMP were not affected. A hypothesis is advanced suggesting that an abnormally high rate of discharge of acetylcholine (and in the later stages of poisoning, its actual accumulation) at central cholinergic synapses causes cyclic GMP levels to rise, perhaps in post-synaptic cells. The elevated cyclic GMP-cyclic AMP ratio found in DDT-poisoned insects may be of fundamental importance in the complex sequence of events leading to tremor, hyperexcitability, paralysis, and death.     

Studies on the uptake and metabolism of adenosine 3':5'-cyclic monophosphate and N6,O2-dibutyryl 3':5'-cyclic adenosine monophosphate in sea urchin eggs

Structurally abnormal mitochondria were found in Candida utilis cells grown in the presence of either high copper concentrations or copper deficiency as compared with cells grown in standard media (copper 60 μg/l). In cells grown under conditions of copper deficiency the average size of the mitochondria is 0.6 μm compared with 0.2 μm of the normal cell, and the cristae have an abnormal appearance. In cells grown in the presence of high copper concentrations the mitochondrial size is up to 2–3 μm with poorly developed cristae and abnormal appearance of the matrix area.     

Effects of adenosine 3':5'-cyclic monophosphate and guanosine 3':5'-cyclic monophosphate on 3H-uridine incorporation into glomerulosal cells of hypophysectomized rat adrenal cortex.

The effects of cyclic AMP and cyclic GMP on the incorporation of 3H-uridine into glomerulosal cells of hypophysectomized rats were investigated by high resolution autoradiography. The quantitative analysis of autoradiographs shows that cyclic nucleotides, like ACTH, enhance the tracer incorporation into both nuclear and mitochondrial compartments. These findings are discussed in relation to previous results indicating that both cyclic nucleotides function as intracellular mediators of the trophic action of ACTH on the rat adrenal zona glomerulosa. The hypothesis that the mechanism of the glomerulotrophic action of ACTH and cyclic nucleotides involves the stimulation of nuclear and mitochondrial RNA synthesis is discussed.     

Renal vein plasma adenosine 3',5'-cyclic monophosphate in renovascular hypertension.

The concentration of plasma adenosine 3'',5''-cyclic monophosphate (cyclic AMP) and plasma renin activity (PRA) were measured concomitantly in blood from both renal veins and in arterial blood in 22 hypertensive patients. In the nine patients with true renovascular hypertension the concentration of plasma cyclic AMP was greater in the venous effluent of the kidney affected by the renal artery stenosis than in that of the unaffected or less affected kidney. The arteriovenous difference in cyclic AMP concentration was less on the affected side in all but one patient. The arteriovenous differences in PRA identified the affected kidney as the source of hyper-reninemia and showed that renin release from the other kidney was suppressed. In the 13 patients with hypertension associated with but unrelated to renal artery stenosis there were no consistent patterns of cyclic AMP concentration or PRA in the venous effluent of the kidneys or of their arteriovenous differences. In renovascular hypertension the venous effluent of the kidney affected by renal artery stenosis contains not only more renin but also more cyclic AMP, owing to either increased cyclic AMP production or decreased excretion or extraction of cyclic AMP by the affected kidney. This unilateral increase in cyclic AMP concentration may become a complementary diagnostic feature of true renovascular hypertension.     

Exercise-induced increases in myocardial adenosine 3',5'-cyclic monophosphate and phosphodiesterase activity

Numerous cellular biochemical events caused by hormones are mediated through cyclic AMP. Although many changes occur in the cell during exercise that could be attributed to this nucleotide, little evidence is available implicating it as an important regulator of exercise metabolism. In this investigation it was found that a 60 min bout of treadmill exercise caused a 2.4-fold increase in myocardial cyclic AMP immediately following the work. Rather than the immediate nucleotide hydrolysis that was expected, it was found that the elevated cyclic AMP level remained for approx. 24 h before returning to control levels. Cardiac glycogen fell to 30% of control after work but supercompensated 60% above control within 1 h following exercise. Therefore, cardiac cyclic AMP was elevated at a time when glycogen was being synthesized. Study of the temporal relationship between the exercise-induced increase in cyclic AMP and cyclic nucleotide phosphodiesterase indicated that the work caused an increase in the hearts' capacity to hydrolyze cyclic AMP. Measurement of heart phosphodiesterase at substrate concentrations of 1.0 and 100 microM produced significant increases in enzyme activity immediately following exercise which remained elevated for 48 h and was back to control activity 96 h following work. These data present a potentially fascinating model for the study of the dissociation between cyclic AMP, glycogenesis and elevations in phosphodiesterase activity in the heart.     

The effects of furosemide on adenosine 3':5'-cyclic monophosphate, guanosine 3':5'-cyclic monophosphate and corticosterone production stimulated by adrenocorticotropin in monolayer cultured rat adrenal cells

Furosemide has been reported to have a suppressive effect on ADH-, PTH- and adrenaline-stimulated adenosine 3':5'-cyclic monophosphate (cAMP) production, but the effect on adrenocorticotropin (ACTH) action has not yet been elucidated. In the present study, therefore, the effects of furosemide on cAMP and also on guanosine 3':5'-cyclic monophosphate (cGMP) and corticosterone, stimulated by ACTH in monolayer cultured rat adrenal cells, were investigated. The intra- and extracellular cAMP stimulated by ACTH was dose-dependently suppressed by furosemide within the concentration range of 10(-3) M to 3 X 10(-3) M, and the suppressive effect of the drug was accompanied with decreased corticosterone production. However, non-stimulated basal corticosterone production was not influenced by the drug even at 3 X 10(-3) M. A similar suppressive effect of dibutyryl cAMP-stimulated corticosterone production by 3 X 10(-3) M furosemide was observed. The intracellular cAMP bound to its binding protein in sonicated adrenal cell extract was also suppressed in a very similar dose-dependent manner to total cAMP. However, though the effect on corticosterone production was also observed when the calcium concentration in the loading medium was changed, the magnitude of the effectiveness (percent of control) was relatively constant at each calcium concentration, suggesting that furosemide may not affect the site(s) at which calcium acts. Intracellular cGMP, on the other hand, was increased by 10(-3) M to 3 X 10(-3) M of furosemide, suggesting an intensifying effect of furosemide on guanylate cyclase activity. Dibutyryl cGMP-stimulated corticosterone production was also increased at the same concentration range. These results indicated that furosemide may act not only on adenylate cyclase but also on the additional step(s) to suppress the resultant corticosterone production. In contrast to the effects of furosemide on such cAMP-mediated processes, this drug treatment appeared to enhance cGMP-mediated corticosterone production.     

Uptake of adenosine 3',5'-cyclic monophosphate and isoproterenol by filarial parasites

The filarial parasites Litomosoides carinii and Dipetalonema viteae both show transcuticular uptake of adenosine 3',5'-cyclic monophosphate but isoproterenol is taken up by D. viteae only. The importance of this difference is discussed from the point of view of metabolic regulation. Inhibition of uptake by lectins indicates the involvement of surface sugar moieties in the transport processes.