Catecholamine stimulation of the gibberellin action that induces lettuce hypocotyl elongation

Effects of catecholamines and their derivatives on gibberellicacid (GA)-induced lettuce hypocotyl elongation was studied,because catecholamines have a chemical structure similar tothe dihydroconiferyl alcohol that has been isolated from lettucecotyledons as a GA synergist. Epinephrine, norepinephrine, dopamineand 3,4-dihydroxymandelic acid synergistically enhanced thepromoting effect of GA on hypocotyl elongation. In contrast,metanephrine, normetanephrine, DOPA and 3-methoxy-4- hydroxymandelicacid did not enhance the GA effect. The action of catecholamineswas inhibited by trans-cinnamic acid which competitively inhibitedthe action of dihydroconiferyl alcohol; this suggests that thereceptor site for catecholamines is the same as that for dihydroconiferylalcohol. The basic ethyl acetate fraction from lettuce seedlingssynergistically enhanced the GA effect. TLC analyses of thisbasic ethyl acetate fraction revealed that the chromatographicarea corresponding to authentic catecholamines could enhancethe GA effect. From these results, a possible role for catecholamines in theregulation of lettuce hypocotyl elongation caused by GA wasposited, and is discussed here. (Received May 15, 1979; )     

Effects of stimulation by carbachol on the metabolism of the bovine adrenal medulla

1. A method is described that has made it possible to achieve a great decrease in the catecholamine and adenine nucleotide contents of the perfused bovine adrenal gland by the infusion of carbachol. 2. Although the catecholamines secreted were recovered in the perfusion medium, no evidence was obtained that the nucleotides are secreted by the gland. 3. It is concluded that the secretion of catecholamines is accompanied by extensive chemical alteration of the adenine nucleotides of the chromaffin granules. 4. The secretory response and the spontaneous release of catecholamines depends on the presence of Ca²⁺ in the perfusing Tyrode solution. 5. Anoxia does not have a significant effect on the carbachol-induced secretion of catecholamines. 6. Strips of bovine adrenal medullary tissue perfused with oxygenated Tyrode solution show an increased oxygen consumption when carbachol is added.     

Plasma free and sulfate conjugated catecholamine levels during acute physiological stimulation in man

The responses of plasma free and sulfate-conjugated catecholamines to acute physiological stimulation was examined in normal male subjects. Catecholamines were measured with a sensitive radioenzymatic assay incorporating simultaneous hydrolysis of sulfate conjugates and O-methylation of free norepinephrine and epinephrine. Following 20 minutes recumbency after venepuncture 30 +/- 3% of norepinephrine and 16 +/- 5% of epinephrine was in thr free form. Free catecholamines generally increased during standing, cold immersion and isometric handgrip, but sulfates did not change. Bicycle ergometry markedly increased free catecholamines which rapidly returned to basal levels at the end of exercise. In contrast, sulfated norepinephrine decreased substantially with exercise in all subjects but returned to basal levels 3 minutes after stopping exercise. Epinephrine sulfate varied considerably between subjects but showed a similar, although smaller, fall with exercise. Thus, during physiological stimulation, which caused increases in free norepinephrine and epinephrine levels in plasma, the only consistent change in sulfated catecholamines was a marked fall in norepinephrine sulfate after bicycle exercise. This may indicate saturation of sulfotransferase activity, substrate inhibition or impaired tissue conjugation.     

Catecholamine stimulation of ion transport in the toad urinary bladder

We have observed that serosal catecholamines increase the amplitude of the short-circuit current (Isc) in the toad urinary bladder by as much as 450%. Chemical sympathectomy with 10(-6) M 6-hydroxydopamine and the sympathomimetic effects of 10(-5) M tyramine indicate a reservoir of amines in the serosal stroma of the tissue. The urinary epithelium from the toad responds to six adrenoceptor agonists: (-)-epinephrine, (-)-norepinephrine, (-)-phenylephrine, clonidine, methoxamine and oxymetazoline. The alpha 2-adrenoceptor agonist clonidine is most potent for stimulating Isc. Some agonists were found to diminish Isc. Apparently this is related to a simultaneous increase in the transepithelial flux of both chloride and sodium. The Isc response to the catecholamines is also inhibited by several adrenoceptor antagonists. The alpha 2-adrenoceptor antagonist yohimbine is more effective than the alpha 1-antagonist prazosin for blocking the stimulation of epithelial transport. As a result of these studies, we have tentatively classified the serosal adrenoceptor of the toad urinary bladder as alpha 2.     

Beta-2-Adrenergic stimulation of ornithine decarboxylase activity in porcine granulosa cells in vitro

Epinephrine, norepinephrine, and isoproterenol produced dose-dependent stimulation of ornithine decarboxylase (EC 4.1.1.17) activity in isolated porcine granulosa cells maintained under defined conditions in vitro. beta- but not alpha-receptor-blocking agents prevented enzyme stimulation by catecholamines. Application of preferential beta-1 and beta-2-receptor antagonists and agonists localized the epinephrine effect to beta-2-adrenergic mediation. Epinephrine action was enhanced by the phosphodiesterase inhibitor, 1-methyl-3-isobutyl-xanthine, but not by saturating concentrations of the cyclic AMP analogue, 8-bromocyclic AMP, of follicle-stimulating hormone, or of prostaglandin E2. However, stimulation by epinephrine was additive to that of luteinizing hormone. Follicular fluid obtained from immature Graafian follicles contained concentrations of norepinephrine and epinephrine active in vitro. Thus, catecholamines may participate in the regulation of ornithine decarboxylase activity in the ovary. Catecholamine effects may be mediated by beta-2-receptors linked to the adenylate cyclase system.     

Blockade of alpha-and beta -adrenergic receptors can prevent stimulation of liver ornithine decarboxylase activity by glucocorticoid or laparatomy.

Rat liver ornithine decarboxylase induction by dexamethasone or laparatomy, which is dramatically impaired by catecholamine depletion, is not affected by alpha-and beta -adrenergic blockers administered simultaneously 1 h prior to steroid injection or operation. However, if blockade is maintained for 24 h, an effect comparable to that of catecholamine depletion is obtained. Reciprocally, the response of the decarboxylase to catecholamines is severely compromised in adrenalectomized rats. Under the same conditions, induction of tyrosine aminotransferase by dexamethasone is not significantly affected by catecholamine availability, which altogether demonstrates that rat liver ornithine decarboxylase activity is specifically governed by the interaction between glucocorticoids and catecholamines.     

Growth stimulation by catecholamines in plant tissue/organ cultures

Addition of catecholamines at micromolar concentrations caused a dramatic stimulation of growth of tobacco (Nicotiana tabacum) thin cell layers (TCLs) and Acmella oppositifolia “hairy” root cultures. A threefold increase in the rate of ethylene evolution was observed in the catecholamine-treated explants. Aminooxyacetic acid and silver thiosulfate, inhibitors of ethylene biosynthesis and action, respectively, reduced the growth-promoting effect of dopamine. However, these compounds alone could also inhibit the growth of the TCL explants. When ethylene in the culture vessel was depleted by trapping with mercuric perchlorate, dopamine-stimulated growth was still obtained, suggesting that ethylene does not mediate the dopamine effect. Dopamine potentiated the growth of TCLs grown in Murashige and Skoog medium supplemented with indoleacetic acid (IAA) and kinetin. When IAA was replaced by 2,4-dichlorophenoxyacetic acid, dopamine addition showed no growth-promoting effect. Instead, 2,4-dichlorophenoxyacetic acid stimulated the growth of TCL explants to the same extent as that obtained with IAA plus dopamine. Because synthetic auxins do not appear to be substrates for IAA oxidizing enzymes, we hypothesized that catecholamines exert their effect by preventing IAA oxidation. Consistent with this explanation, dopamine (25 micromolar) inhibited IAA oxidase activity by 60 to 100% in crude enzyme extracts from tobacco roots and etiolated corn coleoptiles, but had no effect on peroxidase activity in the same extracts. Furthermore, addition of dopamine to TCL cultures resulted in a fourfold reduction in the oxidative degradation of [1-¹⁴C]IAA fed to the explants. Because the growth enhancement by catecholamines is observed in both IAA-requiring and IAA-independent cultures, we suggest that these aromatic amines may have a role in the regulation of IAA levels in vivo.     

Beta-adrenergic stimulation of phagocytosis in the unicellular eukaryote Paramecium aurelia

Bete-adrenergic agonists isoproterenol and norepinephrine enhanced phagocytosis in Paramecium. Stimulation was stereospecific, dose-dependent and inhibited by the beta-agonists propranolol and alprenolol. Phorbol ester and forskolin potentiated the stimulatory effect of catecholamines on Paramecium phagocytosis. The dansyl analogue of propranolol (DAPN) was used for fluorescent visualization of the beta-adrenergic receptor sites in Paramecium which have been found to be localized at the cell membrane and within the membrane of the nascent digestive vacuoles. The appearance of the characteristic fluorescent pattern has been blocked by 1-propranolol.     

β-2-adrenergic stimulation of ornithine decarboxylase activity in porcine granulosa cells in vitro

Epinephrine, norepinephrine, and isoproterenol produced dose-dependent stimulation of ornithine decarboxylase (EC 4.1.1.7) activity in isolated porcine granulosa cells maintained under defined conditions in vitro. β- but not α-receptor-blocking agents prevented enzyme stimulation by catecholamines. Application of preferential β-1 and β-2-receptor antagonists and agonists localized the epinephrine effect to β-2-adrenergic mediation. Epinephrine action was enhanced by the phosphodiesterase inhibitor, 1-methyl-3-isobutyl-xanthine, but not by saturating concentrations of the cyclic AMP analogue, 8-bromocyclic AMP, of follicle-stimulating hormone, or of prostaglandin E₂. However, stimulation by epinephrine was additive to that of luteinizing hormone. Follicular fluid obtained from immature Graafian follicles contined concentrations of norepinephrine and epinephrine active in vitro.Thus, catecholamines may participate in the regulation of ornithine decarboxylase activity in the ovary. Catecholamine effects may be mediated by β-2-receptors linked to the adenylate cyclase system.     

The hormonal stimulation of ureogenesis in isolated hepatocytes through increases in mitochondrial ATP production

Isolated hepatocytes incubated with 2 mm ornithine-10 mm glutamine as substrates and challenged with either glucagon, epinephrine, or phenylephrine exhibited stimulated rates of urea production, and mitochondria isolated from these cells displayed an increased rate of energy-dependent citrulline formation. There was no change in the total carbamyl phosphate synthetase I activity, nor mitochondrial content of the positive effector N-acetyl glutamate after acute hormonal treatment. The time of onset of ureogenesis and its sensitivity to glucagon were compared with stimulation of glucose production from lactate-pyruvate. No apparent differences in time of onset or sensitivity of the responses were observed indicating both pathways may be stimulated by a common mechanism. Mitochondria prepared from cells treated with catecholamines exhibited increased rates of State 3 respiration and increased uncoupler-dependent ATPase activity, in addition to the increased rates of citrulline formation. There was also an elevated intramitochondrial content of ATP and an increased $\text{ATP}\text{ADP}$ ratio. The catecholamine-induced stimulation of ureogenesis was mediated by an α-adrenergic cyclic AMP independent mechanism. The addition of the α-adrenergic antagonist, dihydroergotamine, blocked both the epinephrine-induced stimulation of ureogenesis and also the stimulated functions in the isolated mitochondria. dl-Propranolol, a β-antagonist, inhibited the rise in cyclic AMP due to epinephrine, but had no effect on any of the other reactions measured. The effects of catecholamines on citrulline formation and urea production are correlated with the increased capacity of the mitochondria to generate ATP. It is suggested that both glucagon and catecholamines, acting via independent mechanisms, stimulate electron transport and the activity of the ATP-forming enzyme complex. The consequent elevated intramitochondrial ATP levels and $\text{ATP}\text{ADP}$ ratio enhance the rate of citrulline formation and hence ureogenesis.     

Vasoactive intestinal peptide stimulation of pineal serotonin-N-acetyltransferase activity: general characteristics

Vasoactive intestinal polypeptide (VIP) stimulates basal serotonin-N-acetyltransferase (NAT) activity in pineals in organ culture and enhances the effects of catecholamines in inducing the enzyme. VIP appears to act postsynaptically; its action is independent of the beta receptor and is dependent upon protein synthesis. Its effects may be mediated by a receptor. The magnitude of the pineal response to VIP varies with age, is greater in pineals maintained in 48-h organ culture than in those in acute culture, and can be detected in pineals from newborns after 48-h organ culture. Intravenous administration of VIP can increase pineal NAT activity in vivo.     

Alpha 1-adrenergic stimulation of platelet-derived growth factor A-chain gene expression in rat aorta.

Sympathetic nerves and catecholamines exert growth-promoting trophic influences on arterial smooth muscle in vivo, but the molecular signals mediating these trophic effects are unknown. We report here that the alpha-adrenergic agonist phenylephrine (PE) produced dose-dependent stimulation of platelet-derived growth factor A-chain (PDGF-A) gene expression in rat thoracic aorta via agonist occupancy of alpha 1-adrenergic receptors. Increases in aortic PDGF-A mRNA levels were rapid (maximal at 6 h, 10-fold) and transient. Among seven different tissues studied, PE evoked significant increases in PDGF-A mRNA levels only in the aorta. When periaortic fatty/connective tissues normally adherent to thoracic aorta were examined separately from the remaining aortic vessel wall (endothelium removed), stimulated PDGF-A gene expression was found only in vessel wall (presumably smooth muscle). The physiological alpha-adrenergic agonist norepinephrine also increased aortic PDGF-A mRNA levels. Angiotensin II or endothelin, despite producing blood pressure increases similar to PE, had little or no effect on PDGF-A mRNA abundance in rat aorta. PE-stimulated PDGF-A gene expression was accompanied by increased expression of other growth-related genes including c-fos, c-myc, and ornithine decarboxylase but not DNA synthesis. These results suggest a mechanism for previously described trophic effects of sympathetic nerves and catecholamines on arterial smooth muscle mass, i.e. regulation of growth-related gene expression via alpha 1-adrenergic receptors.     

Steroidogenesis in immature chicken ovary. Hormonal stimulation of adenylyl cyclase system by luteinizing hormone and β-adrenergic agonists

The presence of a hormonally responsive adenylyl cyclase in the immature chicken ovary was investigated. We found that there was a highly significant difference (P< 0. 05) between basal and LH and catecholamine activatable activities. In addition, the basal activity was stimulated by NaF, forskolin and the non-hydrolyzable GTP analogue guanosine-5′-(β, gamma;-imido)-triphosphate (GMPP(NH)P. The action of catecholamines on cyclic AMP and progesterone production was also investigated and compared to that of LH. The stimulatory effect of isoproterenol on cyclic AMP and progesterone production was significantly higher (P< 0.05) than that of LH. The β-adrenergic antagonist propranolol caused complete inhibition of the stimulatory action of catecholamines. Progesterone accumulation induced by LH or isoproterenol was synergistically augmentated by the simultaneous presence of both inducers.     

Insulin-like stimulation of glucose transport in isolated adipocytes by fatty acids

Glucose transport rate as assessed with the 3-0-Methylglucose method was significantly increased in adipocytes preincubated with aliphatic carboxylic acids. The magnitude of stimulation apparently depended on the chain length of the carboxylic acid, and was highest with palmitic acid (130%). The stimulation was additive to the effect of insulin, and reflected a decrease of km rather than an increase in vmax of the transport rate. The results suggest that fatty acids may modulate the activity of the glucose transporter, providing an insulin-dependent supply of adipose tissue with glycerol-phosphate during lipolysis for reesterification of excess fatty acids. Further, it is suggested that fatty acids mediate the stimulatory effect of catecholamines on glucose transport as observed in isolated fat cells.     

Adrenal vein catecholamines and neuropeptides during splanchnic nerve stimulation in cats

Splanchnic nerve stimulation in bursts at low (5 Hz) and high (50 Hz) frequency (30 V, 1 msec; train duration 1 sec; train rate 0.5/second) was employed in 10 cats under halothane anesthesia, during 10-minute periods, while blood samples were concurrently collected from the adrenal vein and femoral artery for the measurement of norepinephrine (NE), epinephrine (EPI), dopamine (DA), Met-enkephalin (ME), neuropeptide Y (NPY), peptide YY (PYY) and neurotensin (NT). In Group I (n = 5), splanchnic nerve stimulation was initially applied at 5 Hz followed after 20 min by a 50 Hz stimulus, while in Group II (n = 5) the stimulation sequence was reversed. Adrenal vein and femoral artery plasma levels of catecholamines and neuropeptides were not significantly affected by the stimulation sequence, while a significant decrease in blood pressure response was observed in Group II during the 5 Hz stimulation as compared to Group I, indicating desensitization. Splanchnic nerve stimulation at 5 Hz caused a preferential increase in adrenal vein NE (9-fold) versus EPI (7-fold) levels as compared to baseline, while 50 Hz stimulation led to further comparable increases in NE (5-fold) and EPI (6-fold) levels. Significant increases in adrenal vein DA and neuropeptide levels were only observed during 50 Hz stimulation, with DA showing a 5-fold, ME a 2.6-fold and NPY a 3-fold increase as compared to 5 Hz stimulation, and NT a 3.6-fold increase as compared to baseline. Present findings indicate different dynamics in the movement of catecholamines and neuropeptides from the adrenal.     

Electric field stimulation releases norepinephrine and cyclic GMP from the rat pineal gland.

Electrical field stimulation caused the release of preloaded ³H-norepinephrine and of cyclic GMP from the rat pineal gland. Increased release of catecholamines and of cyclic nucleotide occurred at low frequency and current, and was largely dependent on the presence of intact nerve endings and extracellular calcium. Presynaptic synthesis and release of cyclic GMP appears to accompany the exocytotic release of neurotransmitter.     

Support for a physiological role of endogenous catecholamines in the stimulation of bovine luteal progesterone production

To determine if catecholamines were present in bovine luteal tissue, corpora lutea (CL) were obtained during the mid-luteal phase (Days 10-12) and the concentration of dopamine (DA) and norepinephrine (NE) was determined by high-performance liquid chromatography. Both DA and NE were detected in luteal tissue at mean concentrations of 41.9 +/- 5.73 and 10.2 +/- 2.51 ng/g for DA and NE, respectively. These concentrations represented a luteal content of 306.6 +/- 66.88 ng/CL for DA and 70.5 +/- 16.88 ng/CL for NE. In vitro, DA at concentrations of 1.0 mM to 0.01 mM stimulated the production of progesterone (P4, p less than 0.05). The response to DA was inhibited by propranolol (a beta-adrenergic receptor antagonist, p less than 0.05) but not by phentolamine, phenoxybenzamine (alpha-adrenergic receptor antagonists), or haloperidol (a DA receptor antagonist, p greater than 0.05). Neither L-tyrosine nor L-dopa altered P4 production (p greater than 0.05). Inhibition of DA beta-hydroxylase, the enzyme that catalyzes the conversion of DA to NE by FLA-63 blocked the DA-induced increases in luteal P4 production (p less than 0.05). These results demonstrate the existence of DA and NE in bovine luteal tissue and indicate that exogenous DA can be converted to NE in luteal tissue. The results support a physiological role for catecholamines in the stimulation of bovine luteal function.     

A behavioral version of catecholamine involvement in new learning rewarded by brain stimulation.

Numerous studies in the rat indicate that catecholamines (CA) mediate rewarding properties of self-administered electrical stimulation to the brain. One such property is the learning of new response-reinforcement relationships. In the present experiment, amphetamine which potentiates CA at the synapse produces stereotypical responding but does not interfere with the learning of new response-reinforcement relationships. Apomorphine, which mimics dopamine (DA) at DA receptors, also produces stereotypy and interferes with learning. The results suggest that DA released by stimulation mediates the stereotyped responding seen in intracranial self-stimulation (ICS) but norepinephrine mediates reward of newly learned responses.     

Effect of stress and cholinergic stimulation on ACTH release in alpha-methyl-dopa pretreated rats

Pituitary-adrenocortical function and the changes of hypothalamic catecholamine content were studied following alpha-methyl-dopa treatment in rats. After three-day administration of alpha-methyl-dopa the plasma corticosterone concentration increased significantly and at the same time ether stress failed to elicit a pituitary-adrenocortical response. Moreover, the alpha-methyl-dopa pretreatment prevented the facilitatory effect of physostigmine on pituitary-adrenocortical activation. As the result of alpha-methyl-dopa treatment the norepinephrine content decreased significantly and the amount of compounds measured as dopamine (dopamine, alpha-methyl-dopamine and alpha-methyl-dopa) increased in the hypothalamus. It is concluded that the impaired metabolism of catecholamines may inhibit the pituitary-adrenocortical activation to stimulation, and that not only norepinephrine and dopamine, but other phenylalanine derivatives and alpha-methyl-dopa may also influence the responsiveness of pituitary-adrenocortical function.