Accumulation Of 3H-noradrenaline Research Articles

Release and disposition of 3H-noradrenaline in the saphenous vein of neonate and adult dogs

Release of 3H-noradrenaline and formation of 3H-metabolites were studied in the saphenous vein of newborn (mean age, 18 h) and adult dogs. Vein strips were incubated with 0.23 mumol/l of 3H-noradrenaline during 1 h and washed out for 110 min; thereafter, the perifusion fluid was collected in 5-min samples. Electrical stimulation was applied at 120 min (1 Hz, 2 ms, 100 V, for 5 min). In some experiments the tissues were preincubated with 1 mmol/l pargyline (to inhibit monoamine oxidase). In these experiments, 12 mumol/l cocaine (to inhibit uptake1), 41 mumol/l hydrocortisone (to reduce uptake2) and 50 mumol/l U-0521 (to inhibit COMT) were present during the perifusion. 3H-noradrenaline, 3H-DOPEG, 3H-NMN, 3H-DOMA and 3H-OMDA were separated by column chromatography. The noradrenaline content of the tissue was estimated by HPLC followed by electrochemical detection. A morphological study was also carried out by light and electron microscopy. The endogenous noradrenaline content of the saphenous vein was 4.3 times higher in adults than in neonates. The number of varicosities was similar in adults and newborns but the number of vesicles per varicosity profile was 5 times higher in adults. Hence, the endogenous noradrenaline content per vesicle was about the same in adults and newborns. The accumulation of 3H-noradrenaline per vesicle was about 5 times higher in newborns than in adults. On the other hand, the vein wall media of neonates was about 3 times thinner than that of adults. The evoked fractional release of tritium was about 10 times higher in neonates than in adults, whether the inactivation pathways were blocked or not.(ABSTRACT TRUNCATED AT 250 WORDS)

Predominance of oxidative deamination in the metabolism of exogenous noradrenaline by the normal and chemically denervated human uterine artery.

Longitudinal strips were prepared from human uterine arteries obtained at hysterectomy. The artery had a low content of noradrenaline and dopamine, contrasting with a high content of the deaminated catechols, dihydroxyphenylglycol (DOPEG) and dihydroxymandelic acid (DOMA), which together represented 98% of endogenous catechols. When incubated with 3H-noradrenaline (0.1 mumol/l), the uterine artery removed, accumulated and metabolized noradrenaline. Deaminated metabolites predominated, DOMA being the most abundant metabolite. Cocaine markedly reduced the accumulation of 3H-noradrenaline and abolished 3H-DOPEG formation, but did not change 3H-DOMA. Selective monoamine oxidase (MAO) inhibitors (clorgyline, selegiline and 2-amino ethyl carboxamide derivatives) caused a marked decrease in the amounts of 3H-DOPEG, 3H-DOMA and 3H-O-methylated and deaminated metabolites (OMDA) formed by the tissue and an increase in 3H-normetanephrine (NMN) formation. Inhibition of catechol-O-methyltransferase suppressed NMN formation and reduced that of OMDA; hydrocortisone slightly depressed the formation of DOMA and OMDA. Homogenates of the uterine artery deaminated 3H-5-HT, 14C-phenylethylamine and 3H-tyramine; inhibition curves of the deamination of 3H-tyramine by clorgyline and selegiline were compatible with the presence of both MOA A and MOA B. Exposure of the strips to 6-hydroxydopamine (1.5 mmol/l for 20 min; 3 exposure periods followed by washout periods of 15,15 and 30 min) resulted in complete and selective chemical denervation of the arterial tissue. This chemical denervation had effects which were similar to those of cocaine. The 2-amino ethyl carboxyamide derivatives markedly reduced the formation of deaminated metabolites by the denervated strips.(ABSTRACT TRUNCATED AT 250 WORDS)

Accumulation of 3H-(�)-noradrenaline by isolated rat liver cells

Using hepatocytes isolated by collagenase perfusion, we studied the accumulation of 3H-noradrenaline. Cells incubated during 15 min in the presence of 0.4 mumol/l 3H-noradrenaline (without inhibition of noradrenaline metabolism) accumulated 8.32 +/- 1.77 pmol/10(6) cells (n = 3). The accumulation of 3H-noradrenaline in isolated parenchymal liver cells was sensitive to 10 mumol/l cocaine (inhibition 36.6 +/- 7.9%, n = 3) and 1 mumol/l desipramine (inhibition 27.2 +/- 6.9, n = 3). Accumulation of 3H-noradrenaline was temperature and sodium dependent (inhibition 33.2 +/- 9.4%, n = 9, when Na+ was replaced by Tris+) and was influenced by the inhibition of the membrane Na(+)-K(+)-adenosine triphosphatase (Na(+)-K(+)-ATPase) by 150 mumol/l ouabain (34.7 +/- 6.9% inhibition, n = 3). Accumulation of 3H-noradrenaline in the hepatocytes was not affected by the presence of uptake2 inhibitors, normetanephrine (30 mumol/l) and corticosterone (30 mumol/l), but was reduced by 30 mumol/l isoprenaline (76.3 +/- 5.0% inhibition, n = 6). Thus, the system that takes up and accumulates noradrenaline in the isolated rat liver cells possesses some characteristics of both, uptake1 and uptake2 systems and appears to be different from other extraneuronal cocaine-sensitive systems, such as the one reported for pulmonary endothelial cells.

Effect of progesterone on the metabolism of noradrenaline in rabbit uterine endometrium and myometrium.

The metabolism of (-)-3H-noradrenaline was examined in the endometrium and the myometrium from rabbits which had received 17 beta-oestradiol, either alone (oestrogen-dominated) or with progesterone (progesterone-dominated). The progesterone treatment resulted in a 2.5-fold increase in 3H-NMN formation in the endometrium, with no change in 3H-DOPEG, 3H-DOMA or 3H-OMDA formation. In the myometrium, progesterone caused a 5-fold increase in 3H-NMN formation and a 2.5-fold increase in 3H-OMDA formation, but did not affect 3H-DOPEG or 3H-DOMA formation. In the progesterone-dominated endometrium, both 3H-NMN and 3H-OMDA formation were strongly inhibited by cocaine 30 mumol/l. When O-methylation was inhibited by a COMT inhibitor, cocaine prevented the resultant increases in deamination of noradrenaline to 3H-DOPEG and in the accumulation of 3H-noradrenaline by the tissue. The 3H-noradrenaline which accumulated in endometria, in which both MAO and COMT were inhibited, was firmly bound; desipramine 3 mumol/l and (+)-amphetamine 10 mumol/l were equieffective with cocaine 30 mumol/l in inhibiting the accumulation. Cocaine 30 mumol/l was without effect on 3H-NMN and 3H-OMDA formation in the progesterone-dominated myometrium, nor did it prevent the increase in 3H-DOPEG formation produced by COMT inhibition. Fluorescent histochemical analysis of the endometrium indicated that the epithelial cells of the endometrial glands were the site of cocaine-sensitive noradrenaline accumulation. It is concluded that progesterone stimulates O-methylation in the endometrium and myometrium in different ways.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of a monoamine oxidase A inhibitor, FLA 668 (+) on the adrenergic mechanisms of the dog saphenous vein

FLA 668 (+) [(S)-(+)-4-amino-2, alpha-dimethylethylphenethylamine (+)-hydrogen bitartrate] selectively inhibited MAO type A in homogenates of dog saphenous vein, with a IC50 of 1 mumol/l for MAO A and greater than 1 mmol/l for MAO B. At concentrations of 1 mumol/l and higher, FLA 668(+) progressively decreased the formation of deaminated metabolites by saphenous vein strips incubated with 3H-noradrenaline, with a preferential action on DOPEG formation. Normetanephrine formation increased but this increase did not wholly compensate for the reduction in the formation of deaminated metabolites. FLA 668(+) caused increased reactivity of saphenous vein strips to noradrenaline and markedly reduced the accumulation of 3H-noradrenaline in the incubated tissue; both effects were still evident in the presence of clorgyline. After cocaine, FLA 668(+) caused no further increase in sensitivity. It is concluded that FLA 668(+) is, in the saphenous vein of the dog, a selective inhibitor of MAO type A and that it exerts a cocaine-like effect.

Chronic sympathetic denervation increases muscarinic cholinoceptor binding in the rat submaxillary gland.

Superior cervical ganglionectomy was found to produce a large decrease in the cocaine-sensitive accumulation of 3H-noradrenaline in the rat submaxillary gland, indicating an effective sympathetic denervation. Six weeks after unilateral denervation the muscarinic cholinoceptor binding of 3H-QNB was increased by over 50% compared to the contralateral, innervated gland. There were no differences in the Kd values between the innervated and denervated glands. These results suggest that changes in muscarinic cholinoceptor density might be in part responsible for the postsynaptic supersensitivity to cholinoceptor agonists observed after chronic sympathetic denervation.

PHENCYCLIDINE AND KETAMINE

In slices of the rat occipital cortex, the influence of phencyclidine and ketamine on the accumulation of 3H-noradrenaline and the subsequent outflow of tritium was investigated, and was compared with the effect of cocaine.-All three drugs inhibited the accumulation of tritium during incubation of the slices with 3H-noradrenaline. Phencyclidine was slightly, whereas ketamine was much less effective than cocaine.-All three drugs accelerated the spontaneous outflow of tritium from slices preincubated with 3H-noradrenaline. The acceleration caused by low concentrations probably reflects an inhibition of the re-uptake of spontaneously released 3H-noradrenaline; in addition, high concentrations (10−4M phencyclidine, 3×10−4–10−3M cocaine and 10−3–3×10−3M ketamine) appear to release tritiated compounds from the neurones. The distance between uptakeinhibiting and releasing concentrations was much greater for cocaine than for phencyclidine and ketamine.-All three drugs enhanced the overflow of tritium evoked by electrical field stimulation. The increase probably reflects an inhibition of the re-uptake of released 3H-noradrenaline; in addition, phencyclidine appears to enhance the release of noradrenaline per pulse.-The actions of phencyclidine and ketamine on central noradrenergic neurones may contribute to the characteristic psychotropic side-effects of these general anaesthetics.

Morphine tolerance and dependence in noradrenaline neurones of the rat cerebral cortex.

By subcutaneous implantation of 2 or 13 morphine pellets (75 mg morphine/pellet), rats were made tolerant to, and dependent on narcotic analgesics. Occipital cortex slices from dependent animals and placebo-implanted controls were incubated with (-)-3H-noradrenaline and subsequently superfused with physiological salt solution. The accumulation of 3H-noradrenaline was not changed by pretreatment with 2, but was slightly decreased by pretreatment with 13 morphine pellets. The overflow of tritium evoked by electrical field stimulation was higher in slices from morphine-implanted rats than in those from placebo controls. Morphine and levorphanol, added in vitro, inhibited the stimulation-induced overflow of tritium at similar concentrations and to a similar degree in slices from morphineand placebo-pretreated animals.--It is concluded that, during chronic treatment with morphine, an adaptation takes place in the brain to compensate for the acute effect of narcotic analgesics, i.e. inhibition of the release of noradrenaline by nerve impulses. The chain of events from the drug-receptor interaction to the depression of the release process can be escluded as substrate of this adaptation. During withdrawal, the compensatory changes provoke an enhanced increase of extracellular noradrenaline during nerve impulses.

Effects of some tetrahydrocannabinols on the biosynthesis and utilization of catecholamines in the rat brain

Publisher Summary This chapter describes the effects of some tetrahydrocannabinols on the biosynthesis and utilization of catecholamines in the rat brain. Determinations of the endogenous content of homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC) in the corpus striatum were made, to gain a better insight into the metabolism of dopamine in this region. All three cannabinols had the same qualitative effect on catecholamine accumulation and release. The accumulation of 3H-noradrenaline, and of 3H-dopamine was increased. Their effect on 3H-noradrenaline was marked, whereas their effect on 3H-dopamine was much less pronounced. The increases produced by Δ9-THC and by Δ8-THC were of the same order of magnitude, and slightly smaller than those caused by DMHP. The effects of the cannabinols on the disappearance of 3H-catecholamines paralleled their effects on its accumulation. 3H-noradrenaline utilization was markedly accelerated to a similar extent by all three cannabinols. The disappearance rate of 3H-dopamine, however, was not significantly altered by Δ9-THC, and Δ8-THC. The mean values showed a trend toward a greater disappearance rate, but increased utilization was only observed after treatment with DMHP.

Uptake and accumulation of 3H-noradrenaline in adrenergic nerves of rat iris. Effect reserpine, monoamine oxidase and tyrosine hydroxylase inhibition

Isolated rat irides were incubated in Krebs-Ringer bicarbonate buffer containing 3H-noradrenaline ( 3H-NA) and the 3H-NA taken up was determined. The extracellular space determined with 14C-sorbitol was about 40% of the iris. The equilibration and clearing of the extracellular space occured within 15 min incubation time. Four pharmacologically different uptake models for NA were used: irides from untreated rats, nialamide pretreated rats, reserpine + nialamide pretreated rats and H44/68 (synthesis inhibitor) pretreated rats. Specific chemical determinations disclosed that very small amounts of metabolites are formed in the iris preparation after an in vitro incubation. It was concluded that there is an efficient uptake and accumulation of NA in adrenergic nerves of rat iris. The membrane pump seemed to be the dominant and most important mechanism for the initial uptake while the granular uptake mechanism was of importance for the total storage capacity and intraneuronal retention. Reserpine did not affect the axonal membrane uptake to any significant degree. After pretreatment with a synthesis inhibitor, H44/68, the uptake and accumulation of 3H-NA in the iris was only increased 10–20% compared to the untreated iris, indicating that the depleted NA stores were not completely refilled. The extraneuronal uptake was very small provided that the medium concentration of NA was not too high (10 −6 M or lower). This uptake increased considerably in relation to the neuronal uptake when NA concentrations of 10 −5 M of higher were used, although there was no true accumulation of amine in the tissue compared with the medium.

Uptake and accumulation in vitro of 3H-noradrenaline in adrenergic nerves of human atrium.

The adrenergic innervation and the in vitro uptake of 3H-noradrenaline has been investigated in human atrial tissue slices from patients undergoing thoracic surgery. The atrial appendage was richly innervated, but the density of the adrenergic nerve plexus varied considerably between different tissues examined. The nerve terminals were of characteristic varicose appearance, running singly or in bundles along the long axis of the muscle fibers. The nerve fibers seemed to penetrate in between the muscle cells. The distribution and appearance of the adrenergic nerves were quite similar to those described in earlier investigations of heart tissue from other species. The uptake and accumulation of 3H-noradrenaline in vitro increased with increasing concentration in the medium and with time, and the uptake process could efficiently be blocked by desmethylimipramine (DMI), a potent inhibitor of the uptake mechanism located at the axonal membrane, the so called ‘membrane pump’. There was a true accumulation of 3H-noradrenaline in the atrial tissue during the incubation, compared to the medium. The metabolism of 3H-noradrenaline during the incubation has also been studied. The data presented speak in favour of the view that the adrenergic nerves of human atria possess an efficient uptake accumulation mechanism for noradrenaline.

The accumulation of 3H noradrenaline by the lung

3H noradrenaline injected into mice in high doses is accumulated in considerable amounts by the lungs. Reserpine and tyramine which decrease noradrenaline stored in adrenergic nerve endings (heart) do not decrease this monoamine in the lung. The fact that 3H noradrenaline is accumulated by the lung mainly when higher doses are injected and results with both depleting agents (reserpine and tyramine) support the idea of extraneuronal storage sites. The possible storage site of monoamine in the lung and the role of this organ in removing physiologically active substances is discussed.