Effects of beta-adrenergic stimulation on bone-marrow function in normal and sublethally irradiated mice. I. The effect of isoproterenol on cAMP content in bone-marrow cells in vivo and in vitro.

The effect of isoproterenol (IPR) on bone-marrow cAMP content was investigated in vivo and in vitro. In unirradiated CFW mice, the bone-marrow cAMP content was found to be elevated by the administration of noradrenaline, adrenaline and isoproterenol. After IPR administration, the increase in cAMP was biphasic with maxima at 1 and 15 min. An increase in cAMP content was also noted in bone-marrow of sublethally-irradiated mice, but no further increase was observed 15 min after the administration of IPR. Elevation of cAMP by either IPR or radiation was prevented by pretreatment with the beta-adrenergic blocking agent--propranolol. IPR was also effective in increasing the cAMP content when added to suspension of bone-marrow cells. This effect was abolished by propranolol. IPR did not increase cAMP levels in bone-marrow cells isolated from irradiated animals. The results suggest that the differentiated bone-marrow cells have beta-adrenergic receptors.     

Effect of adrenaline on the mitosis-inhibiting action of a chalone-containing preparation in Ehrlich ascites tumor

The effect of adrenaline and Ehrlich ascite carcinoma (EAC) chalone on cell division was studied. It has been established that EAC chalone inhibited cell proliferation. The action of adrenaline was also accompanied by a decrease in mitotic index, but the inhibitory effect of the hormone was weaker than that of chalone, it occurred later and its duration was less. A combined effect of adrenaline and chalone depended on the time interval between the administration of the substances. It has been found that chalone administration 1 h after adrenaline administration prolonged mitotic inhibitory effect by 4 h and its synchronous action on cell division in EAC was weak during the experiment. Combined effect of adrenaline and chalone did not differ from the effect of chalone alone if chalone was administered 3 h after adrenaline administration.     

The inotropic action of adrenergic substances on the heart ventricles during the ontogeny of the frog Rana temporaria

The effects of adrenaline and other adrenergic drugs on the isolated, electrically driven ventricles and ventricular strips from the tadpoles, the first year froglets and adult frogs have been studied. Adrenaline induced positive inotropic effect at all developmental stages including the earliest one, stage 32 (stages were determined according to Dabagian and Sleptsova). The pharmacological analysis revealed the beta-adrenergic origin of this effect. The sensitivity to adrenaline decreased after the stage 43 and became the lowest in adult hearts. It may partly be due to maturing of the neuronal uptake mechanism because the sensitivity to isoproterenol which is not subjected to the neuronal uptake processes was not decreased in the adults as compared to tadpoles. The adrenoceptors of the tadpole heart have the higher affinity to propranolol then the adrenoceptors of the adult heart.     

Hepatic venoconstrictor effects of isoproterenol and nifedipine in anesthetized cats

In cats anesthetized with pentobarbital, isoproterenol infused into a peripheral vein causes a reduction in hepatic blood volume measured by plethysmography. As this response is accompanied by increases in portal and hepatic lobar venous pressures, the decrease in hepatic volume cannot be a passive emptying secondary to reduced intrahepatic pressure. We conclude that intravenous isoproterenol causes an active hepatic venoconstriction. Nifedipine produced similar responses. From this and our previous data, we conclude that in anesthetized cats, arteriolar vasodilators which increase cardiac output cause hepatic venoconstriction (hydralazine, adrenaline, dopamine, isoproterenol, and nifedipine), while those which do not increase cardiac output have no effect on the hepatic venous bed (nitroprusside and diazoxide) or cause venodilatation (nitroglycerine). The mechanism of the hepatic venoconstrictor effect of isoproterenol was investigated further. Because previous work has shown that this response does not occur when isoproterenol is infused locally into the hepatic artery or portal vein, the venoconstrictor effect of peripheral intravenous infusions must be indirectly mediated. The response was still present after hepatic denervation, adrenalectomy, nephrectomy, and after indomethacin administration indicating it is not mediated by the hepatic nerves, adrenal catecholamines, the renal renin-angiotensin system, or prostaglandins. The mechanism remains unknown.     

Unequal effects of renin-angiotensin system inhibitors in acute cardiac dysfunction induced by isoproterenol

Several clinical trials have demonstrated that angiotensin-converting enzyme inhibitor (ACEI) and angiotensin II type 1 receptor blocker (ARB) are equally effective in the treatment of chronic heart failure. However, this has not been confirmed for acute cardiac dysfunction. We examined whether ACEI or ARB prevents isoproterenol-induced acute left ventricular (LV) dysfunction in dogs. LV dysfunction induced by a large dose of isoproterenol (1 microg.kg(-1).min(-1), 3-h infusion) was compared in dogs treated with ACEI (temocaprilat) or ARB (olmesartan). Atrial pacing induced a constant heart rate and use of adjustable aortic banding provided a nearly constant afterload. LV systolic function (LV dP/dt, fractional shortening, and ejection fraction) and diastolic function (tau and LV end-diastolic pressure) were significantly deteriorated after isoproterenol infusion. The LV dysfunction was almost totally prevented by ARB but was only partially prevented by ACEI. The partial effect of ACEI was complemented by cotreatment with HOE-140, a bradykinin B2 receptor antagonist. At baseline, the response to low doses of isoproterenol was significantly attenuated by ACEI but not by ARB, and the ACEI-induced attenuation was totally abolished by cotreatment with HOE-140. The response to isoproterenol was significantly attenuated after 3 h of excess isoproterenol loading, and it was almost completely preserved by ARB but not by ACEI. In conclusion, acute LV dysfunction and beta-adrenergic desensitization induced by excess isoproterenol administration were almost totally prevented by ARB but only partially prevented by ACEI. These differences were attributable at least in part to bradykinin pathways activated by ACEI administration in acute LV dysfunction.     

Agonist-Induced Regulation of Adrenoceptor Subtypes in Cerebral Cortical Slices

Cerebral cortical slices from rat brain were incubated at 37 degrees C for 2 h in the presence of isoproterenol, noradrenaline, or adrenaline, and binding affinities and densities of adrenoceptor subtypes were subsequently examined in homogenized tissue. The density of alpha 2- and total beta-adrenoceptors was estimated using the radioligands [3H]rauwolscine and [3H]dihydroalprenolol (DHA), respectively. The percentages of beta 1- and beta 2-adrenoceptors were defined by inhibiting the binding of [3H]DHA with the beta 1-selective antagonist metoprolol. Exposure of slices to noradrenaline and adrenaline significantly decreased the maximal number of binding sites (Bmax) of alpha 2-adrenoceptors (48 and 37% respectively) without significantly affecting affinity; isoproterenol had no effect. Exposure to isoproterenol, noradrenaline, and adrenaline significantly decreased the Bmax of beta-adrenoceptors (by 60, 34, and 24%, respectively) but did not affect the affinity. Isoproterenol and adrenaline significantly decreased the density of beta 1-adrenoceptors by 75 and 24% and beta 2-adrenoceptors by 23 and 28%, respectively. Noradrenaline significantly decreased the density of beta 1-adrenoceptors by 42% without affecting the number of beta 2-adrenoceptors. These findings indicate that subtypes of adrenoceptors in rat cerebral cortex are differentially regulated by adrenergic agonists.     

Neuropeptide tyrosine (NPY)-induced potentiation of the pressor activity of catecholamines in conscious rats

IV bolus administration of 2.5-50 micrograms NPY (0.6-12.5 nmol) to conscious rats produced a dose- and time-dependent increase in systolic and diastolic blood pressure. Following priming with 2.5 micrograms NPY, or larger doses, the subsequent administrations of noradrenaline produced pressor responses that were potentiated both in magnitude and duration. The NPY-induced potentiation of the pressor response to noradrenaline was dose-dependent and extended to the pressor action of adrenaline and angiotensin II but not to the hypotensions produced by bradykinin or isoproterenol. The potentiation was not related to the fact that multiple doses of catecholamines were repeated. Reserpine did not substantially modify the NPY-induced potentiation of the pressor activity of the catecholamines. Chemical sympathectomy following 6-hydroxydopamine caused a marked supersensitivity to the catecholamines and NPY but obliterated the NPY-induced potentiation of the pressor effect of adrenaline. Nifedipine reduced the pressor action of the catecholamines and NPY but did not attenuate the NPY-induced potentiation of the pressor action of catecholamines. It is concluded that the acute pressor effect of NPY and of the potentiation of the catecholamine pressor effects involve different mechanisms.     

The effects of propranolol, phentolamine, and atropine on canine coronary vascular gradients

The objective of this study was to measure pressure gradients in the coronary circulation following the administration of three receptor-blocking drugs, propranolol, phentolamine, and atropine when administered singly and in sequence. As well, we examined the responses of these gradients to eight interventions: left stellate ganglion or left vagosympathetic trunk stimulation, administration of isoproterenol, acetylcholine, noradrenaline, adenosine, phenylephrine, or adrenaline. Using a multiple linear regression model we examined the actions and interactions of the receptor-blocking agents on hemodynamic variables and vascular gradients. Propranolol reduced heart rate as expected and blocked the responses to isoproterenol administration. As well, it abolished the epicardial coronary artery diastolic gradient. The gradient was restored when propranolol was the second receptor blocker administered but was abolished when it was the third. Phentolamine induced vasodilation with a decrease in coronary small vessel gradients. This effect persisted without regard to the sequence of administration. When it was the second or third agent it decreased the microcirculation and small vein gradients, an action it did not manifest when given singly. Atropine singly did not alter pressures or gradients; but as the second agent it altered the transmural, outflow tract, epicardial diastolic, and microcirculation and small vein diastolic gradients; and as the third agent the changes were in the transmural, epicardial systolic and diastolic, and small artery systolic and diastolic gradients. The pattern of responses was not predictable and that indicates that unique changes occur in the responses of the coronary circulation when multiple receptor-blocking agents are employed. Adrenergic control tends to dominate in the coronary arterial circulation, and muscarinic control in the coronary microcirculation and veins with considerable overlap.     

Limited depletion of central adrenaline stores following administration of adrenaline synthesis inhibitors in rats

The aim of the present study was to maximise the selective depletion of adrenaline stores in the rat brainstem and spinal cord, obtained by administering inhibitors of adrenaline synthesis. Partial depletions of adrenaline in the hypothalamus and medulla were observed after a single injection of either LY134046 or SKF 64139 (40 mg/kg i.p.). The rate and extent of depletion seen in the hypothalamus 3 or 6 h after a single dose of LY134046 could be increased by simultaneous exposure to cold or by lowering blood pressure, but not by prior administration of the synthesis inhibitor at 12 h intervals for 3 days. None of the treatments used were able to significantly lower spinal cord adrenaline levels, despite at least 80% inhibition of spinal cord PNMT activity. These results suggest that the ability to reduce central adrenaline stores by synthesis inhibition is limited, especially in the spinal cord.     

Effects of isoproterenol treatment on the parathyroid glands in golden hamsters of different ages, with special reference to the frequency of lipid droplets

The frequency of lipid droplets in the parathyroid glands of young, adult and senile golden hamsters after treatment with isoproterenol was investigated. In the parathyroid glands of the young and senile animals the number of lipid droplets increased gradually by 1 h, and thereafter it remained almost unchanged at 3 h after administration. In the glands of adult animals it increased, at first rapidly and then gradually, by 3 h after administration. It is considered that in the parathyroid glands of the golden hamsters stimulated by isoproterenol there is a relationship between the number of lipid droplets and aging.     

Protection by endogenous FGF-2 against isoproterenol-induced cardiac dysfunction is attenuated by cyclosporine A

Fibroblast growth factor-2 (FGF-2) is implicated in cardioprotection. However, previously we found that chronic elevation in cardiac FGF-2 levels in transgenic mice was associated with exaggerated, cyclosporine A-preventable, cellular infiltration after isoproterenol-induced injury, suggestive of an adverse outcome, although this was not examined with functional studies. We have now used highly sensitive tissue Doppler imaging (TDI) to evaluate cardiac functional parameters after isoproterenol administration in transgenic mice overexpressing the 18 kDa FGF-2 in the heart in vivo. Cardiac function was assessed in conscious FGF-2 transgenic and non-transgenic mice at 24 h as well as 2 and 4 weeks after isoproterenol administration, and in the absence or presence of either cyclosporine A or anti-CD3ε treatments. Isoproterenol decreased left ventricular endocardial velocity and strain rate by 47-51% at 24 h in non-transgenic mice, but to a significantly lesser extent (by 24%) in transgenic mice. While additional decreases were seen in non-transgenic mice at 2 weeks, there was no further reduction in ventricular endocardial velocity or strain rate up to 4 weeks post-treatment in FGF-2 transgenic mice. Functional improvement at 2 and 4 weeks post-isoproterenol was reduced significantly by treatment with cyclosporine A but not anti-CD3ε; the latter targets T lymphocyte activation more specifically. TDI values in the presence of chronic FGF-2 overexpression are prognostic of an improved cardiac outcome and protection from isoproterenol induced cardiac dysfunction in vivo. Our data also suggest that cyclosporine A-sensitive infiltrating cell population(s) may contribute to the sustained beneficial effect of FGF-2 in vivo.     

Metabolic interactions of glucose, acetoacetate and adrenaline in rat submaxillary gland in vitro.

1. The metabolic interactions between glucose, acetoacetate and adrenaline were studied in submaxillary-gland slices. 2. Acetoacetate (2.5 mM) inhibited glucose removal by 22% and entry of glucose carbon into the tricarboxylic acid cycle by 54%. 3. Acetoacetate caused an increase in (glucose 6-phosphate) together with an increase in (citrate), a finding that suggests that the phosphofructokinase step might be inhibited by the elevated (citrate). Support for this suggestion was obtained in experiments in which fluoracetate was used to elevate (citrate). 4. A further site of action of acetoacetate at the pyruvate dehydrogenase step was suggested by an increase in the lactate+pyruvate pool, and the finding that pyruvate removal and (3-14C)pyruvate oxidation were inhibited by acetoacetate. 5. Adrenaline, a stimulator of secretion by this tissue, increased glucose removal by 25%. Adrenaline increased glucose removal to the same extent when acetoacetate was also present in the incubation medium. In both cases the increase was accompanied by a fall in (glucose 6-phosphate). 6. Adrenaline also overcame the inhibition of pyruvate removal caused by acetoacetate. 7. The tissue (ATP) decreased by about 50% on addition of adrenaline, and a similar fall was observed in vivo after adrenergic stimulation by isoproterenol. 8. Omission of Ca-2+ from the medium prevented the fall in (glucose 6-phosphate) and (ATP) caused by adrenaline, although adrenaline was still able to stimulate glucose removal. The inhibitory effect of acetoacetate on gluocse removal was reversed by adrenaline, but there was no stimulation above the control rates. Inhibition of pyruvate removal by acetoacetate was not overcome by adrenaline in the absence of Ca-2+. 9. Dibutyryl cyclic AMP had no effect on glucose removal or on (ATP). 10. Possible mechanisms by which adrenaline can bring about its metabolic effects are discussed.     

Effect of different beta-blocking drugs and adrenaline on the conversion of thyroxine to triiodothyronine in isolated rat hepatocytes

The in vitro effect of various selective and non-selective beta-blocking drugs and adrenaline on the conversion of thyroxine (T4) to triiodothyronine (T3) was studied in suspensions of isolated rat hepatocytes after 90 min of incubation. Compared with the untreated controls propranolol caused a dose-related inhibition of the T4 to T3 conversion in conc of 100, 200 and 400 microM. The other beta-blocking drugs studied, timolol, oxprenolol, atenolol and metoprolol, were without any effect on this in vitro conversion. Propranolol did not interfere with the cellular association of T4 or the degradation of T4 and T3. Adrenaline 200 microM caused a small decrease of T3 in the medium and a corresponding increase in the intracellular content of T3. The inhibitory effect of propranolol 200 microM was not antagonized by equimolar concentrations of adrenaline. Our study suggests that the inhibitory effect of propranolol on the conversion of T4 to T3 in hepatocytes is caused by a direct chemical effect of the drug unrelated to its beta-blocking and membrane stabilizing properties.     

Calcium metabolism and amylase release in rat parotid acinar cells.

1. A method is described for the isolation of rat parotid acinar cells by controlled digestion of the gland with trypsin followed by collagenase. As judged by Trypan Blue exclusion, electron microscopy, water, electrolyte and ATP concentrations and release of amylase and lactate dehydrogenase, the cells are morphologically and functionally intact. 2. A method was developed for perifusion of acinar cells by embedding them in Sephadex G-10. Release of amylase was stimulated by adrenaline (0.1-10muM), isoproternol (1 or 10 MUM), phenylephrine (1 muM), carbamoylcholine (0.1 or 1 muM), dibutyryl cycle AMP (2 MM), 3-isobutyl-1-methylxanthine (1mM) and ionophore A23187. The effects of phenylephrine, carbamoylcholine and ionophore A23187 required extracellular Ca2+, whereas the effects of adrenaline and isoproterenol did not. 3. The incorporation of 45Ca into parotid cells showed a rapidly equilibrating pool (1-2 min) corresponding to 15% of total Ca2+ and a slowly equilibrating pool (greater than 3h) of probably a similar dimension. Cholinergic and alpha-adrenergic effectors and ionophore A23187 and 2,4-dinitrophenol increased the rate of incorporation of 45Ca into a slowly equilibrating pool, whereas beta-adrenergic effectors and dibutyryl cyclic AMP were inactive. 4. The efflux of 45Ca from cells into Ca2+-free medium was inhibited by phenylephrine and carbamoylcholine and accelerated by isoproterenol, adrenaline (beta-adrenergic effect), dibutyryl cyclic AMP and ionophore A23187. 5. A method was developed for the measurement of exchangeable 45Ca in mitochondria in parotid pieces. Incorporation of 45Ca into mitochondria was decreased by isoproterenol, dibutyryl cyclic AMP or 2,4-dinitrophenol, increased by adrenaline, and not changed significantly by phenylephrine or carbamoylcholine. Release of 45Ca from mitochondria in parotid pieced incubated in a Ca2+-free medium was increased by isoproterenol, adrenaline, dibutyryl cyclic AMP or 2,4-dinitrophenol and unaffected by phenylephrine or carbamoylcholine. 6. These findings are compatible with a role for Ca2+ as a mediator of amylase-secretory responses in rat parotid acinar cells, but no definite conclusions about its role can be drawn in the absence of knowledge of the molecular mechanisms involved, their location, and free Ca2+ concentration in appropriate cell compartment(s).     

Is the damaging action of catecholamines on the myocardium realized via hyperstimulation of the beta receptors?

Experiments on an isolated rat heart were made to compare the damaging action on the myocardium of catecholamines (noradrenaline, adrenaline and isoproterenol) differing in the affinity for beta-receptors. The damage to myocardial cells was evaluated from the release into the perfusate of intracellular enzymes (creatine phosphokinase and lactate dehydrogenase) and the number of contracture damaged myocytes. Noradrenaline exerted the most powerful damaging action on the myocardium at a concentration of 10(-6) M. Perfusion of the heart with isoproterenol at concentrations of 10(-6) M and 10(-5) M did not lead to the affection of cardiomyocytes. It was isoproterenol concentration exceeding noradrenaline concentration 100 times that produced an increase in the rate of the release of the enzymes to the perfusate and a rise of the number of contractures in the myocardium, with the above increase being less than that provoked by adrenaline and noradrenaline (10(-6) M). It is concluded that the mechanism of the cardiotoxic effect of catecholamines cannot be reduced only to their effect on myocardial beta-receptors.     

Enhancement of In Vivo Antioxidant Ability in the Brain of Rats Fed Tannin

The effect of the oral administration of mimosa tannin (MMT) on the rat intra-hippocampal antioxidant ability was examined. Wistar rats at the age of 6 weeks were reared for 8 weeks with the rodent diet (RD) consisting of 0.1 g/kg of MMT (RD–MMT). The antioxidant ability of rat brain was evaluated from the decay of a brain–blood-barrier permeable stable nitroxide, 3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (PCAM) measured by the microdialysis-electron spin resonance system under a freely moving state. The decay rate of PCAM in the brain of rats fed RD–MMT was significantly larger than that of rats fed control rodent diet, which indicates the increase of the antioxidant ability in the brain of rats fed RD–MMT. In vitro study showed that MMT did not reduce PCAM directly but enhanced the reduction of PCAM by ascorbic acid. These results indicate that MMT is a potent antioxidant in vitro and in vivo.     

Comparison of metabolic effect of ammonia and adrenaline infusions in sheep.

Intravenous infusions of ammonium chloride (62.3 mumol.kg-1.min-1) for 30 min caused a significant increase in blood glucose, lactate, pyruvate and free fatty acid (FFA) levels. A similar effect was also observed during infusion of adrenaline. Propanolol--a beta-receptor blocking agent--completely prevented the rise of blood pyruvate and lactate after adrenaline when 8.3 microgram.kg-1.min-1 of propranolol were infused, but not after NH4Cl administration. Lipolytic actions of adrenaline were completely prevented but that of NH4Cl was only significantly diminished by blockade of beta-receptors with propranolol. It was concluded that the influence of ammonium ions on blood lactate and pyruvate and FFA was not entirely mediated by adrenaline.     

Hormonal control of gluconeogenesis in tubule fragments from renal cortex of fed rats. Effects of α-adrenergic stimuli, glucagon, theophylline and papaverine

1. In incubated tubule fragments from renal cortex of fed rats gluconeogenesis from pyruvate was stimulated by adrenaline (1mum optimum) and by the selective alpha-adrenergic agonists oxymetazoline and amidephrine. The selective beta-agonists isoproterenol and salbutamol were ineffective at concentrations up to 10mum. 2. Stimulation of gluconeogenesis by 1mum-adrenaline was almost completely blocked by 10mum-phentolamine (alpha-antagonist), partially blocked by 10mum-phenoxybenzamine (alpha-antagonist) and unaffected by 10mum-propranolol (beta-antagonist). 3. Adrenaline stimulation of gluconeogenesis was rapid and was sustained for at least 1h. 4. Oxymetazoline (alpha-agonist) was extremely potent in stimulation of gluconeogenesis. This compound stimulated glucose production from pyruvate, lactate and glutamate, but not from succinate or glycerol. 5. In the absence of Ca(2+) oxymetazoline was ineffective, whereas some stimulatory effect of adrenaline on gluconeogenesis was still observed. 6. Glucagon had no effect on gluconeogenesis from pyruvate in the presence of 1.27mm-Ca(2+) and inhibited the process in the presence of 0.25mm-Ca(2+). Parathyrin (parathyroid hormone) stimulated gluconeogenesis at 1.27mm-Ca(2+). 7. In short incubations of tubule fragments glucagon, papaverine and adrenaline significantly increased 3':5'-cyclic AMP. Adrenaline also slightly decreased 3':5'-cyclic GMP. Oxymetazoline had no effect on the amount of either cyclic nucleotide. 8. At all concentrations tested, theophylline and papaverine decreased gluconeogenesis from pyruvate. 9. It is concluded that renal gluconeogenesis may be increased by alpha- but not beta-adrenergic stimuli and that this is probably independent of changes in 3':5'-cyclic AMP or 3':5'-cyclic GMP. An involvement of Ca(2+) in the action of oxymetazoline appears likely, but this is less certain with adrenaline.