Isoproterenol-treated Rat Research Articles

Circ-sh3rf3/GATA-4/miR-29a regulatory axis in fibroblast-myofibroblast differentiation and myocardial fibrosis.

The transdifferentiation from cardiac fibroblasts to myofibroblasts is an important event in the initiation of cardiac fibrosis. However, the underlying mechanism is not fully understood. Circ-sh3rf3 (circular RNA SH3 domain containing Ring Finger 3) is a novel circular RNA which was induced in hypertrophied ventricles by isoproterenol hydrochloride, and our work has established that it is a potential regulator in cardiac hypertrophy, but whether circ-sh3rf3 plays a role in cardiac fibrosis remains unclear, especially in the conversion of cardiac fibroblasts into myofibroblasts. Here, we found that circ-sh3rf3 was down-regulated in isoproterenol-treated rat cardiac fibroblasts and cardiomyocytes as well as during fibroblast differentiation into myofibroblasts. We further confirmed that circ-sh3rf3 could interact with GATA-4 proteins and reduce the expression of GATA-4, which in turn abolishes GATA-4 repression of miR-29a expression and thus up-regulates miR-29a expression, thereby inhibiting fibroblast-myofibroblast differentiation and myocardial fibrosis. Our work has established a novel Circ-sh3rf3/GATA-4/miR-29a regulatory cascade in fibroblast-myofibroblast differentiation and myocardial fibrosis, which provides a new therapeutic target for myocardial fibrosis.

Nerolidol attenuates isoproterenol-induced acute myocardial infarction in rats.

Cardiovascular diseases have high morbidity and mortality rates, and their treatment is not effective in reducing the damage caused by myocardial infarction (MI). This study aimed to investigate whether nerolidol (NRD), a sesquiterpene alcohol, could attenuate MI in an isoproterenol-treated rat model. MI was induced by the administration of two doses of isoproterenol (ISO, 100mg/kg, i.p.) with an interval of 24h between doses.The animals were divided into four groups: control (CTR) (vehicle - NaCl 0.9% + Tween 80 0.2%), MI (ISO + vehicle), MI + NRD (50 mg/kg) and MI + NRD (100 mg/kg). An electrocardiogram was performed, and contractile parameters, cardiac enzymes, infarction size, and antioxidant parameters in the heart were measured to evaluate the effects of NRD. The ISO group showed a significant rise in ST segment, QTc, and heart rate associated with a reduction in left ventricular developed pressure (LVDP), + dP/dt, and -dP/dt. In addition, there were increases in levels of creatine kinase (CK), creatine kinase-myocardial band (CK-MB), lactate dehydrogenase (LDH), and thiobarbituric acid (TBARS); reductions in superoxide dismutase (SOD) and catalase (CAT) activities; and an increase in the infarction size. Interestingly, NRD significantly attenuated almost all the parameters of ISO-induced MI mentioned above. Our results suggest that nerolidol attenuates MI caused by ISO by a marked reduction in myocardial infarct size and suppression of oxidative stress. CK total, creatine kinase total; CK-MB, creatine kinase myocardial band; LDH, lactate dehydrogenase; SOD, superoxide dismutase; CAT, catalase. CTR (vehicle group), MI (100mg/kg of isoproterenol), ISO + NRD 50 (50mg/kg of nerolidol), and ISO + NRD 100 (100mg/kg of nerolidol).

Modification of levosimendan-induced suppression of atrial natriuretic peptide secretion in hypertrophied rat atria

This study aimed to determine the effects of levosimendan, a calcium sensitizer, on atrial contractility and atrial natriuretic peptide (ANP) secretion and its modification in hypertrophied atria. Isolated perfused beating rat atria were used from control and isoproterenol-treated rats. Levosimendan and its metabolite OR-1896 caused a positive inotropic effect and suppressed ANP secretion in rat atria. Similar to levosimendan, the selective phosphodiesterase 3 (PDE3) or PDE4 inhibitor also suppressed ANP secretion. Suppression of ANP secretion by 1 µM levosimendan was abolished by PDE3 inhibitor, but reversed by PDE4 inhibitor. Levosimendan-induced suppression of ANP secretion was potentiated by KATP channel blocker, but blocked by KATP channel opener. Levosimendan alone did not significantly change cyclic adenosine monophosphate (cAMP) efflux in the perfusate; however, levosimendan combined with PDE4 inhibitor markedly increased this efflux. The stimulation of ANP secretion induced by levosimendan combined with PDE4 inhibitor was blocked by the protein kinase A (PKA) inhibitor. In isoproterenol-treated atria, levosimendan augmented the positive inotropic effect and ANP secretion in response to an increased extracellular calcium concentration ([Ca+]o). These results suggests that levosimendan suppresses ANP secretion by both inhibiting PDE3 and opening KATP channels and that levosimendan combined with PDE4 inhibitor stimulates ANP secretion by activating the cAMP–PKA pathway. Modification of the effects of levosimendan on [Ca+]o-induced positive inotropic effects and ANP secretion in isoproterenol-treated rat atria might be related to a disturbance in calcium metabolism.

The cardioprotective effects of a combination of quercetin and α-tocopherol on isoproterenol-induced myocardial infarcted rats.

The present study aims to evaluate the combined protective effects of quercetin and α-tocopherol on isoproterenol-treated myocardial infarcted rats. Male albino Wistar rats were pretreated with a combination of quercetin (10 mg/kg) and α-tocopherol (10 mg/kg) daily for 14 days. After the pretreatment, rats were injected isoproterenol (100 mg/kg) to induce myocardial infarction. Isoproterenol-treated rats showed increased levels of serum troponins and increased intensities of serum lactate dehydrogenase-1 and -2 isoenzyme bands. Isoproterenol treatment also showed significant decreased levels of antioxidant system and significant increased levels of plasma lipid peroxidation, plasma uric acid, and the heart calcium. Furthermore, isoproterenol-treated rat's electrocardiogram showed elevated ST segments. Combined pretreatment with quercetin and α-tocopherol normalized all the biochemical parameters and minimized the alterations in electrocardiogram. Histopathology of myocardium also confirmed the cardioprotective effects of quercetin and α-tocopherol. In vitro studies confirmed the mechanism of action of quercetin and α-tocopherol. Thus, quercetin and α-tocopherol exhibited cardioprotective effects against isoproterenol-induced cardiotoxicity due to their scavenging free radicals, improving antioxidants and maintaining Ca(2+) levels. Our study also showed that combined pretreatment (quercetin and α-tocopherol) was highly effective than single pretreatment (quercetin or α-tocopherol).

Expression and localization of prominin-1 in isoproterenol-treated rat parotid gland

Prominin-1 (CD133) is a pentaspan cholesterol-binding membrane glycoprotein. Chronic treatment with isoproterenol, a beta-receptor agonist, induces several dramatic effects on salivary glands, such as enhanced DNA synthesis and proliferation of salivary acinar cells. In addition, the biosynthetic pathways of membrane lipids may be altered by the isoproterenol stimulation. The purpose of this study was to investigate the effect of isoproterenol administration on prominin-1 expression profiles in rat parotid gland by means of PCR and immunohistochemistry. Rats were chronically treated with the beta-adrenergic agonist for 1, 3, and 7 days. Our results showed that isoproterenol-treatment caused a down-regulation of prominin-1 on day 3 and 7 of treatment, as well as a differential immunostaining distribution pattern. This study suggests that isoproterenol-treatment may represent a useful tool to explore the molecular mechanisms involved in the synthesis and release of prominin-1. Such efforts could contribute to the development of diagnostic tools based on the detection of prominin-1 in biological fluids, such as saliva.

Cardioprotective effect of fluvastatin on isoproterenol-induced myocardial infarction in rat

The present study was designed to investigate whether fluvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, would attenuate the acute myocardial infarction in isoproterenol-treated rat model via maintaining activities of endogenous antioxidant enzymes. Hemodynamic and electrocardiograph parameters were monitored and recorded continuously, cardiac marker enzymes and antioxidative parameters of plasma and heart tissues were measured, and histopathological examination of heart tissues was performed. Isoproterenol-treated rats showed lower of left-ventricular systolic pressure (LVSP), maximum (LVd P/d t max) and minimum rate of developed left ventricular pressure (LVd P/d t min), and higher of left ventricular end-diastolic pressure (LVEDP), in addition, a significant rise in ST-segment and increase in content of lactate dehydrogenase, glutamic oxalacetic transaminase, creatine kinase and malondialdehyde, as well as fall in activities of glutathione peroxidase, superoxide dismutase and catalase were observed. Oral administration of fluvastatin (5, 10 and 20 mg/kg, respectively) significantly prevented almost all the parameters of isoproterenol-induced heart failure and myocardial injury that mentioned above. The protective role of fluvastatin on isoproterenol-induced myocardial damage was further confirmed by histopathological examination. There was no significant change in heart rate in all experimental groups. Compared with control group, any indexes in sham rats treated with fluvastatin (20 mg/kg) alone were unaltered (all P > 0.05). Our results suggest that fluvastatin has a significant effect on the protection of heart against isoproterenol-induced myocardial infarction through maintaining endogenous antioxidant enzyme activities.

Silibinin Protects Rat Cardiac Myocyte from Isoproterenol-Induced DNA Damage Independent on Regulation of Cell Cycle

Silibinin, derived from the milk thistle plant, Silybum marianum, has been traditionally used as an antihepatotoxic agent for the treatment of liver disease. Our preliminary study demonstrated that silibinin has protected rat cardiac myocytes against beta-adrenergic agonist isoproterenol-induced injury through resuming mitochondrial function and regulating the expression of SIRT1 and Bcl-2 family members. In this study, we investigate whether silibinin has anti-apoptotic effect on isoproterenol-treated rat cardiac myocytes. DNA damage, detected by the TUNEL and DNA fragmentation assay, was diminished after treatment of silibinin. Results of nitrite and Western blot assays showed that the amount of NO and the expression of iNOS were decreased after treatment with silibinin, while the expression of procaspase-3 and digestion of caspase-3 substrates, the inhibitor of caspase-activated DNase (ICAD) and poly-(ADP-ribose) polymerase (PARP), were increased simultaneously. The DNA damage was reversed by down-regulation of p53 phosphorylation after treatment with silibinin. Result of flowcytometric analysis showed that the cell cycle was not affected, and the expression of cell cycle regulatory protein p21 also had no change. Consequently, silibinin protected cardiac myocytes against isoproterenol-induced DNA damage through caspase pathway and the expression of p53, but independent on regulation of cell cycle.

Silibinin Protects Against Isoproterenol-Induced Rat Cardiac Myocyte Injury Through Mitochondrial Pathway After Up-regulation of SIRT1

Terminally differentiated adult injured cardiac myocytes have been used for various animal models of heart failure. It has recently been shown that isoproterenol induces injury in rat neonatal cardiac myocytes via a β-adrenergic pathway, suggesting that it might be one of the factors involved in myocardial cell injury in heart failure in vivo. In the study, silibinin, a plant flavanoid from milk thistle was first evaluated for its protective effect against β-adrenergic agonist isoproterenol-induced injury in cultured rat neonatal cardiac myocytes. The viability, activation of lactate dehydrogenase (LDH), and content of maleic dialdehyde (MDA) were chosen for measuring the degree of cardiac myocytes injury. As a result, silibinin protected isoproterenol-treated rat cardiac myocytes from death and significantly decreased LDH release and MDA production. Silibinin increased superoxide dismutase activity, decreased [Ca2+]i, and increased mitochondrial membrane potential (∆Ψ). Furthermore, the release of pro-apoptotic cytochrome c from mitochondria was reduced by silibinin. Silibinin increased the expression of anti-apoptotic Bcl-2 family protein Bcl-2, and up-regulation of SIRT1 inhibited the translocation of Bax from cytoplasm to mitochondria, which caused mitochondrial dysfunction and cell injury. These results demonstrate that silibinin protects against isoproterenol-induced cardiac myocytes injury through resuming mitochondrial function and regulating the expression of SIRT1 and Bcl-2 family members.

Tetramethylammonium is a muscarinic agonist in rat heart.

Studies were designed to determine if tetramethylammonium (TMA), a quaternary amine that structurally resembles the cationic portion of acetylcholine, can affect cardiac function by acting on muscarinic receptors. Experiments examined effects of this cation on 1) the spontaneous beating rate of right atrial preparations isolated from rats, 2) force of contraction in isoproterenol-treated (0.1 microM) rat papillary muscle, and 3) quinuclidinyl benzilate ([3H]QNB) binding to rat ventricular membranes. TMA elicited concentration-dependent (0.5-50 mM) negative chronotropic and negative inotropic actions that were antagonized by the muscarinic receptor antagonist atropine. Radioligand studies showed that TMA acts as both a competitive and noncompetitive antagonist of [3H]QNB binding; the apparent dissociation constant for [3H]QNB was increased (0.092 +/- 0.025 nM in the absence of TMA; 1.14 +/- 0.204 nM in the presence of 50 mM TMA), whereas binding site density was decreased (148 +/- 26 and 65 +/- 4 fmol/mg in the absence and presence of 50 mM TMA, respectively). These results suggest that extracellular TMA can alter the function of rat heart by stimulating muscarinic receptors. This action should be considered when using this quaternary amine as a cation substitute.

Tracheal Potential Difference in the Reserpine and Isoproterenol Rat Models of Cystic Fibrosis

Basic research into cystic fibrosis (CF) has been hampered by the lack of a suitable animal model. Reserpinized or isoproterenol-treated rats have been proposed as models because they exhibit certain morphological and physiological features characteristic of CF. Recent evidence suggests that abnormal epithelial transport of Na+ [corrected] and Cl- may underlie pathogenesis, defects that may contribute to the markedly more negative transepithelial electrical potential differences (PD) recorded in CF airways compared with controls. To test the models further, we measured tracheal PD in vivo in treated rats (reserpinized - 6.9 mV, SEM 0.7 mV, n = 7; isoproterenol-treated -10.2 mV, SEM 1.5 mV, n = 12) and found it to be no different from that of controls (-8.7 mV, SEM 0.6 mV, n = 25). The animals did, however, demonstrate a reduced gain in body weight as well as increased submaxillary gland weight, which reflected an increased mucus content in the acini. These observations suggest that although the reserpinized or isoproterenol-treated rat may be useful in the study of the pathogenesis of exocrine disturbances in disease, their use as models for the effect of the basic defect of CF in the airways may be limited.

31P NMR spectroscopy of hypertrophied rat heart: Effect of graded global ischemia

To investigate the cause for the greater susceptibility of hypertrophied hearts to ischemic injury, we determined the interrelations of total work output, contractile function and energy metabolism in isolated, perfused normal and hypertrophied rat hearts subjected to graded global ischemia. Cardiac hypertrophy was induced by giving rats seven daily injections of either triiodothyronine (0.2 mg/kg) or isoproterenol (5 mg/kg). All hearts were perfused at an aortic pressure of 100 mmHg in the isovolumic mode in an NMR spectrometer (7.05 Tesla). Heart rate, developed pressure, and coronary flow were monitored simultaneously with changes in pH, creatine phosphate, ATP and inorganic phosphate. During pre-ischemic perfusion, the total work output (rate-pressure product) of hyperthyroid hearts was 28% higher than that of control hearts, whereas hearts from isoproterenol-treated animals showed no difference. However, when related to unit muscle mass, work was normal in hyperthyroid hearts and 26% lower after isoproterenol. Contractile function per unit myocardium (developed pressure/g wet weight) was lower in the hypertrophied hearts. ATP content was the same in all groups. Creatine phosphate decreased 41% after triiodothyronine and 25% after isoproterenol. Inorganic phosphate levels and intracellular pH were similar in control and isoproterenol-treated rat hearts, but were higher in the hyperthyroid rat hearts. The phosphorylation potential and the free energy change of ATP hydrolysis were lowered by hypertrophy, the levels correlating with the depressed contractile function. At each ischemic flow rate, both work and contractile function per unit myocardium were the same for all hearts, but the relations between flow and phosphorylation potential were different for each type of heart. Thus, at low flow rates, hypertrophied hearts perform the same amount of work and have the same contractile function as control hearts, but with abnormal changes in energy metabolism, indicating that the relations of energy status to coronary flow, total work output and contractile function are altered during the process of hypertrophy.

Comparison of phospholipid N-methylation activity in rat submandibular salivary gland and liver

Successive phospholipid N-methylation from phosphatidylcholine to phosphatidylethanolamine in submandibular gland and liver microsomes proceeded without the addition of exogenous phospholipid substrate. Methylation activity in the submandibular microsomes showed different susceptibilities to various detergents than the liver enzyme and also partially required Mg 2+. However, the three methylation steps could not be distinguished by their Mg 2+ requirements. Ca 2+ had no effect on the activity. The methylation activity in submandibular gland was much lower than in liver. Chronic administration of isoproterenol, which causes an increase of phosphatidylcholine in membrane phospholipids of salivary glands, decreased methylation activity in the submandibular gland. Thus the increase in phosphatidylcholine in isoproterenol-treated rat salivary glands may not be derived from the phospholipid methylation pathway, but may be due to stimulation of other routes of phosphatidylcholine metabolism.

Inducing effects of chronic administration of isoproterenol on 1-acyl-sn-glycero-3-phosphate and 1-acyl-sn -glycero-3-phosphocholine acyltransferases in rat parotid salivary gland

1. 1. In rat parotid gland, chronic administration of isoproterenol caused significant increase of linoleic acid and decrease of arachidonic acid at the sn-2 position of phosphatidylcholine. 2. 2. The activities of 1-acyl-sn-glycero-3-phosphate and 1-acyl-sn-glycero-3-phosphocholine acyl-transferases were increased 3–8-fold and 2-fold, respectively, in the parotid gland microsomes of isoproterenol-treated rat. 3. 3. Furthermore, the specificity of these two enzymes for various acyl-CoAs was also changed by administration of isoproterenol. 4. 4. The alteration of unsaturated fatty acid composition at the sn-2 position of phosphatidylcholine was at least in part due to the change of activity and substrate specificity of lysophospholipid acyltransferases.

O-193 - Effect of Nicorandil against the infarct-like myocardial lesion of isoproterenol-treated rat

O-193 - Effect of Nicorandil against the infarct-like myocardial lesion of isoproterenol-treated rat

Molecular cloning and chromosomal localization of human 4-beta-galactosyltransferase.

A cDNA clone to human 4-beta-galactosyltransferase (EC 2.4.1.38) was isolated from a human liver lambda gt11 expression library by using a monospecific polyclonal antiserum to affinity-purified bovine enzyme. The authenticity of this cDNA clone has been demonstrated by several criteria. Under conditions of chronic treatment with the beta-adrenergic receptor agonist isoproterenol, rat parotid glands show an approximately 10-fold increase in 4-beta-galactosyltransferase activity. The increased enzyme activity was reflected in dot-blot analysis of control and isoproterenol-treated rat parotid RNA by using the human cDNA as probe. Hybrid-selection and in vitro translation identified a protein product with a molecular mass of 47 kDa that was immunoprecipitated with the bovine antiserum. The full-length human cDNA clone was then isolated and the DNA sequence for the NH2-terminal portion of the protein was deduced. Comparison of the NH2-terminal protein sequence from the bovine protein with that of the human cDNA clone confirmed its identity. In addition, the human cDNA clone was used to localize the gene for 4-beta-galactosyltransferase to human chromosome 4 by Southern analysis of a somatic cell hybrid panel.

Mitosis and Hypertrophy of Intercalated Duct Cells and Endothelial Cells in the Isoproterenol-treated Rat Parotid Gland

Chronic treatment of rats with isoproterenol (IPR) induces mitosis and differentiation of intercalated duct cells, and mitosis and hypertrophy of endothelial cells of the microvasculature in the parotid gland. Mitoses occurred in duct cells situated at or near the acinar-intercalated duct junction, and were most numerous after six IPR injections. These cells increased in size, contained numerous electron-lucent granules, and were incorporated into the hypertrophic acini. The granules contained branching filamentous or finely reticulated material, and did not react with histochemical stains for carbohydrate. Capillary and venule endothelial cell mitoses were frequently seen after four to six IPR injections. The endothelial cells increased in thickness, contained abundant cytoplasmic organelles, lacked fenestrations, and had few pinocytotic vesicles. These results demonstrate the extensive nature of the response to chronic IPR treatment, and are consistent with the concept that the intercalated ducts have an important role in salivary gland physiology.

The chronically isoproterenol-treated rat in the study of cystic fibrosis: X-ray microanalysis of the submandibular gland

The chronically isoproterenol-treated rat has been proposed as an animal model for cystic fibrosis. Ultrastructural studies showed enlarged cells with abnormally large mucus granules that were more often fused than in control animals. X-ray microanalysis of mucous acinar cells showed a significant increase in calcium levels, but unaffected magnesium levels. Combined treatment with isoproterenol and reserpine caused a very large increase in cellular calcium levels that appeared to be an addition of the single effects and increased magnesium levels (as in glands of rats treated with reserpine only). Chronic treatment with isoproterenol, reserpine, or both substances tended to decrease cellular potassium levels. Chronic exposure to the specific β 1-agonist prenalterol or the specific β 2-agonist terbutaline did not affect cellular calcium or potassium levels. It is concluded that chronic isoproterenol treatment affects the elemental composition of mucous acinar cells of rat submandibular gland differently from chronic reserpine treatment. The increase in cellular calcium concentration after chronic isoproterenol treatment does not appear to be due to an effect via β-adrenergic receptors.

Induction of protein and glycoprotein synthesis in rat submandibular glands by isoproterenol.

A family of proline-rich proteins which contain over 40% proline and a glycoprotein were isolated from submandibular glands of isoproterenol-treated rats by extraction with 10% trichloroacetic acid and fractionation of the acid-soluble portion on Bio-Gel A-1.5m. The proline-rich proteins were subsequently separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Proteins were detected by formaldehyde fixation and Coomassie staining. After elution from the gels, amino acid compositions were determined. The family of proline-rich proteins (about six) appears to be qualitatively identical with a family of proteins from parotid glands of isoproterenol-treated rats (Muenzer J., Bildstein, C., Gleason, M., and Carlson, D. M. (1979) J. Biol. Chem. 254, 5623-5628, 5629-5634), except for a substantial change in the relative amount of each protein. An acid-soluble glycoprotein (GP-158) was not detected in extracts of submandibular glands of normal rats, but GP-158 was highly induced by isoproterenol treatment. This glycoprotein has an apparent Mr = 158,000 as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The major amino acids were Asx, 13%; Glx, 18%; Pro, 29% and Gly, 11%. GP-158 contained about 37% carbohydrate, and its sugar composition on a molar basis was mannose, 3.0; galactose, 2.1; N-acetylglucosamine, 3.5; fucose, 1.2; and sialic acid (N-glycolyl(4-O-acetyl)neuraminic acid), 0.9. N-Acetylgalactosamine was not detected. A glycopeptide isolated from GP-158 had the same sugar composition as GP-158. The amino acid sequence of the glycopeptide was shown to be Asp-Gly-(Asn)-Gln-Thr-Gln-Pro-Arg-Pro-(Gly-Pro). Only the parotid and submandibular glands of rats responded in this dramatic fashion to isoproterenol. The isoproterenol-treated rat is considered an appropriate model system for studying the overall effects of catecholamine beta-agonists on gene expression in these secretory tissues.

Cell-free translations of proline-rich protein mRNAs.

Treatment of rats with the beta-agonist isoproterenol causes a dramatic increase in a series of proteins rich in proline (proline-rich proteins) in the parotid glands (Muenzer, J., Bildstein, C., Gleason, M., and Carlson, D. M. (1979) J. Biol. Chem. 254, 5623, 5629). These proteins which contain about 43% proline, comprise more than 50% of the total soluble protein of glands of rats treated with isoproterenol for 10 days. Further studies by in vitro translation analysis using the reticulocyte lysate system and labeling with [3H]proline or [35S]methionine show definitive changes in patterns of protein synthesis and proline-rich protein mRNAs are highly elevated in treated animals. Analysis of translation products by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed (1) very little synthesis of proline-rich proteins from poly(A+) RNA of glands of normal rats, (2) poly(A+) RNA from glands of treated animals synthesize mainly proline-rich proteins, (3) translations with [3H]proline and [35S]methionine give identical labeling patterns from cell-free translations are all precipitated by antibodies to proline-rich proteins. At least six different proline-rich proteins are translated with poly(A+) mRNA from glands of treated animals. Each of these proteins is likely a translation product of a separate, specific mRNA. The dramatic changes in protein synthesis of rat parotid glands in response to isoproterenol treatment suggest to us that the parotid gland of the isoproterenol-treated rat is an excellent model system to study the overall responsiveness of gene expression to catecholamines.