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)     

Effect of catechol oestrogens on extraneuronal metabolism of noradrenaline by rabbit uterine endometrium and myometrium

Summary The effects of 2-hydroxy and 2-methoxy oestrogens on the extraneuronal O-methylation of ³H-(–)noradrenaline were examined in progesterone-dominated, monoamine oxidase (MAO)-inhibited, rabbit uterine tissues in vitro. Both the corticosteroid- sensitive system in myometrium and the cocaine-sensitive system in endometrium were examined.In myometrial slices preincubated with nialamide to inhibit MAO and incubated with cocaine to inhibit neuronal uptake, ³H-normetanephrine (³H-NMN) formation was inhibited in the order of potency 2-hydroxy oestrone 2-hydroxy oestradiol = 2-methoxy oestradiol 2-methoxy oestrone. In myometrial slices not exposed to cocaine and nialamide, inhibition of ³H-NMN formation by both 2-hydroxy and 2-methoxy oestradiol did not affect the formation of deaminated metabolites of ³H-(–)-noradrenaline by the alternative metabolising pathway. In endometrial slices preincubated with nialamide to inhibit MAO, only 2-hydroxy oestrogens inhibited ³H-NMN formation, but they were one to two orders of magnitude less potent in this regard than in the myometrium. The uptake of ³H-(–)-noradrenaline by MAO- and COMT-inhibited myometrial slices was inhibited by 2-hydroxy and 2-methoxy oestrogens in the order of potency 2-methoxy oestradiol 2-methoxy oestrone 2-hydroxy oestrone > 2-hydroxy oestradiol. Uptake of ³H-(–)-noradrenaline by endometrial slices was not affected by either 2-hydroxy or 2-methoxy oestrogens.It is concluded that the O-methylatiog system for noradrenaline in myometrial tissue is more sensitive than that in endometrial tissue to the inhibitory actions of 2-hydroxy and 2-methoxy oestrogens. 2-Hydroxy oestrogens inhibit ³H-NMN formation by competing for COMT rather than noradrenaline uptake sites, since (1) they inhibited O-methylation but not uptake of ³H-noradrenaline in endometrium and (2) 2-hydroxy oestrogens were two orders of magnitude more potent against ³H-NMN formation than ³H-(–)-noradrenaline uptake in myometrium. In contrast, the ability of 2-methoxy oestrogens to inhibit myometrial but not endometrial ³H-NMN formation reflects the selective inhibitory effect of 2-methoxy oestrogens on the corticosteroid-sensitive uptake system for noradrenaline which predominates in myometrium but is minimal in endometrium. These interactions may be important in pregnancy when the local concentrations of catechol and methoxy oestrogens rise.     

The effect of pregnancy on the metabolism of noradrenaline in reproductive organs of the rabbit

The influence of counter irritation by turpentine on carrageenan-oedema, leucocyte count, plasma kininogen stores and composition of sponge-induced exudates has been investigated in the rat. Counter irritation reduced the carrageenan-oedema in normal as well as in adrenalectomized rats. It induced leucopenia with lymphopenia but did not modify the plasma kininogen stores. In turpentine-pretreated rats, the exudates induced by sponge implantation 18 h previously had a lower content in leucocytes. Their levels in beta-glucuronidase and beta-galactosidase were slightly reduced, their content in PGE2 was not modified and their level in malonaldehyde was increased. The exudates induced by sponge implantation 4 h previously had a lower content in leucocytes and PGE2 while their level in kinins was not modified. The mechanism of the anti-inflammatory effect of counter irritation by turpentine is discussed. We suggest that the main factor involved is a decrease in leucocyte accumulation into the exudates.     

Effect of intra-uterine administration of indomethacin on ovarian steroids

Proteolytic enzymes increase the sensitivity of the bronchial system against acetylcholine when inhaled as aerosols. These experiments were performed on 33 dogs in order to localize the area of sensitivity in the bronchial system responsible for bronchoconstriction. Pronase given in a small dosage as proteolytic enzyme aerosol only to the upper part of the airtract sensitises the lower part of the airways against acetylcholine. Pronase aerosol given to the lower part of the airways needs higher dosages for sensitization to acetylcholine. This effect assumes an interaction between the upper sensoric part in the reflex way of airway obstruction and the lower airways. Changes caused by proteolytic enzymes in the upper part of the airtract can cause increased reactivity of the lower airways.     

The actions of histamine on the separated layers of the guinea-pig uterus: the influence of ovarian steroids

The effects of histamine have been studied on separated circular and longitudinal myometrial layers from the guinea-pig. Virgin guinea-pigs in dioestrus were (1) untreated, (2) treated for 14 days thrice weekly with oestradiol cypionate 20 micrograms/kg s.c., or (3) treated as in (2) but in addition with progesterone 3 mg/animal s.c. daily for 4 days before use. Preparations were field-stimulated (60 V 2 ms 30 Hz for 5 s every 100 s) to elicit regular contractions. Histamine was equipotent in producing enhancement of evoked contractions of circular myometrium from animals in each treatment group (pD2 = 5.03, 5.05 and 4.95 in groups 1, 2 & 3 respectively), and enhanced contractility in all but two longitudinal myometrial preparations. Treatment with oestradiol alone, and with oestradiol and progesterone following oestradiol priming enhanced the magnitude of maximal response and produced a small decrease in the potency of histamine on the longitudinal myometrium. pA2 estimates for mepyramine as an antagonist were similar (8.6) in preparations of longitudinal myometrium from each group of animals. Metiamide (1-10 mumol/l) did not antagonise the effects of histamine in this layer. These results, taken together, indicate that ovarian steroids act selectively on the longitudinal myometrial layer to amplify the action of histamine, but do not alter the histamine receptor subtype which in this layer is exclusively H1.     

Effects of the oestrous cycle and exogenous ovarian steroids on metabolism of beta-phenylethylamine in rat lung.

1 Metabolism of [14C]-beta-phenylethylamine (PEN), a substrate for monoamine oxidase-B (MAO-B), was measured in lung homogenates and in perfused lungs during the 4 day oestrous cycle of the rat. 2 Metabolism in vitro was high during met-oestrus and di-oestrus and low during pro-oestrus and oestrus; this variation in activity correlated with changes in Vmax of the enzyme without changes in Km. 3 PEN metabolism in lung homogenates was also altered by treatment of rats with 17 beta-oestradiol but not by progesterone treatment. 4 Metabolism of [14C]-PEN in perfused lungs was the same during either pro-oestrus or met-oestrus. Uptake of [14C]-PEN in perfused lung measured directly was also the same at these two stages. 5 These results demonstrate that in lungs MAO-B activity was affected by endogenous changes in steroid level but that such changes in enzymic activity were not reflected in the metabolic properties of whole lung.     

Studies on the cardiotoxicity of noradrenaline in isolated rabbit hearts

The concentration-dependent toxic effects of exogenous noradrenaline (NA, CAS 51-41-2) on acute regional myocardial ischemia (MI) was investigated with and without alpha- and beta-adrenoceptor blockade. Electrically-driven rabbit Langendorff-hearts with depleted catecholamine stores were used (reserpin 7.0 mg/kg i.p. 16-24 h before preparation, constant pressure: 70 cm H2O, Tyrode solution, Ca2+ 1.8 mmol/l). Repetitive MI, separated by a reperfusion period of 50 min, was induced by coronary artery branch ligature, and quantitated from epicardial NADH-fluorescence photography. Starting after a reperfusion period of 20 min, hearts were treated with exogenous NA (10(-7), 10(-6) or 10(-5) mol/l). Adrenoceptors were blocked by propranolol (10(-6) mol/l) and phentolamine (10(-6) mol/l). Without adrenoceptor blockers, NA 10(-6) mol/l induced an increase in left ventricular pressure and a reduction in the relative coronary flow. Concomitantly, MI was enhanced. After adrenoceptor blockade, NA 10(-7) or 10(-6) mol/l had no influence on functional parameters. MI was not affected by NA 10(-7) mol/l, but MI was significantly enhanced by NA 10(-6) mol/l. MI enhancement by NA 10(-6) mol/l was completely prevented by superoxide dismutase (30 U/ml). Functional effects of NA 10(-5) mol/l were not completely inhibited by adrenoceptor blockers at the concentrations used, and arrythmias were observed. MI was also enhanced by NA 10(-5) mol/l. CONCLUSION: Deleterious effects on MI, that are independent on functional effects, are induced by NA in a micromolar concentration. These direct toxic effects are mediated by superoxide anion radicals. In lower concentrations (10(-7) mol/l), there is no evidence for direct toxic actions of NA independent of functional effects. MI enhancement by NA 10(-5), or 10(-6) mol/l without adrenoceptor blockers may have been caused in part by functional and arrythmogenic effects and/or through the generation of oxygen free radicals.     

Actions of forskolin and isoprenaline on the separated myometrial layers of the guinea-pig uterus: influence of ovarian steroids and pregnancy

Responses to forskolin and isoprenaline of electrically stimulated preparations of longitudinal and circular myometrium were compared. The guinea-pigs used were: untreated (dioestrous), ovarian steroid-treated, pregnant and post-partum. Forskolin inhibited electrically evoked contractions of both myometrial layers obtained from all groups; there was no change in its potency or its maximum effect (90-100% inhibition). The inhibition of contractions of longitudinal myometrium by isoprenaline was enhanced with steroid treatment, attaining a maximum in late pregnancy and immediately post-partum. In circular myometrium, there was no significant change in the potency of isoprenaline on tissues from ovarian steroid-treated animals. However, maximum potency as well as maximum response was observed in late pregnancy. Since the effects of isoprenaline but not of forskolin were modulated, we suggest that ovarian steroids and pregnancy may alter the coupling of beta-adrenoceptors to the adenylate cyclase system.     

Effect of omega-conotoxin GVIA on noradrenaline release from postganglionic sympathetic neurones in rabbit aorta

The aim of the present work was to examine the effect of the selective N-type calcium blocking agent omega-conotoxin GVIA on stimulation-evoked release of noradrenaline from sympathetic nerves in rabbit isolated aorta with regard to stimulation frequency, extracellular Ca2+ concentration, and transmitter uptake. Rings of rabbit isolated aorta were preloaded with (-)-3H-noradrenaline and the fractional 3H-overflow evoked by electrical-field stimulation was determined by liquid scintillation spectrometry. Omega-conotoxin GVIA (3 x 10(-10)-3 x 10(-8) M) did not alter the spontaneous 3H-outflow. Omega-conotoxin GVIA (3 x 10(-10)-3 x 10(-8) M) caused a slowly developing reduction of stimulation-evoked 3H-overflow at 1 and 30 Hz. The Emax for the omega-conotoxin-induced inhibition was less (70%) at 30 Hz than that (96%) seen at 1 Hz. Short-term incubation with omega-conotoxin GVIA caused a subsequent steady-state inhibition. The inhibitory action of omega-conotoxin GVIA (3 x 10(-10)-3 x 10(-9) M) was inversely related to the extracellular Ca2+ concentration (6.5 x 10(-4)-2.7 x 10(-3) M). Cocaine (3 x 10(-5) M) plus corticosterone (4 x 10(-5) M), neuronal and extraneuronal uptake inhibitors, respectively, did not alter the inhibitory effect of omega-conotoxin GVIA (3 x 10(-9) M) on 3H-overflow evoked by stimulation at a frequency of either 1 or 30 Hz. It is concluded that omega-conotoxin GVIA acts on prejunctional N-type calcium channels to inhibit stimulation-evoked noradrenaline release from sympathetic neurone terminals in rabbit aorta. At a high frequency, another subtype calcium channel may possibly be involved. The action of omega-conotoxin GVIA is independent of neuronal and extraneuronal uptake mechanisms for noradrenaline, but dependent on the amount of Ca2+ to be transported across the neurilemma from the extracellular space into the neurone.     

Effect of blood on the response of the rabbit ear artery to noradrenaline and angiotensin II

Blood or plasma added to the perfusing Krebs solution potentiated the vasoconstrictor effects of noradrenaline and angiotensin II on the isolated ear artery of the rabbit. The relatively greater increase in the vasoconstrictor effect of angiotensin II in the presence of blood or plasma may account for part of its potent pressor activity in vivo.     

ACTH increases noradrenaline release in the rabbit heart

Summary The effects of ACTH on the release of noradrenaline and the increase of heart rate produced by sympathetic nerve stimulation (1 Hz) were studied in isolated perfused rabbit hearts. ACTH-(1–24) 0.1–100 nmol/l increased the stimulation-evoked overflow of noradrenaline concentration-dependently, reversibly and up to two-fold. The basal outflow of noradrenaline, the basal heart rate and the stimulation-evoked increase in heart rate were not changed. Human ACTH-(1–39) also increased the evoked overflow of noradrenaline. The effect of ACTH-(1–24) 0.3 nmol/l persisted after blockade of -adrenoceptors with propranolol and blockade of neuronal catecholamine uptake by cocaine. ACTH-(1–24) 3 nmol/l did not change the removal of noradrenaline from the perfusion fluid, when hearts were perfused with medium containing 59 nmol/l noradrenaline. The results show that ACTH increases the action potential-evoked release of noradrenaline from cardiac postganglionic sympathetic neurones, probably by activating specific presynaptic ACTH receptors. The high potency of ACTH suggests that these presynaptic receptors may be activated in vivo by circulating ACTH under certain pathophysiological conditions.Send offprint requests to B. Szabo at the above address     

The effect of adrenaline, noradrenaline and isoprenaline on the guinea-pig uterus

The actions of adrenaline, noradrenaline and isoprenaline were compared on the isolated guinea-pig uterus. In uteri from immature animals (200 to 350 g) adrenaline caused relaxation which changed to a biphasic effect and finally to a contraction in the course of an experiment (6 to 8 hr). Noradrenaline always caused contraction and isoprenaline relaxation. In uteri from oestrogen-treated animals adrenaline and noradrenaline caused contraction and isoprenaline caused relaxation. Isoprenaline potentiated the contraction produced by adrenaline and reversed the adrenaline relaxation to a contraction. The change of the pharmacological action of adrenaline was not related to the Na⁺ and K⁺ content of the uterus, which remained constant throughout an experiment involving repeated application of the amines. Nor could it be related to a change in the glycogenolytic effect of adrenaline estimated by determinations of total glycogen of the muscle which, however, may not reflect a momentary change in rate of breakdown.     

Dual effect of adrenaline on noradrenaline release in the pithed rabbit

We examined the effects of adrenaline on the noradrenaline release rate and plasma catecholamine levels in the pithed rabbit with electrically stimulated sympathetic outflow (3 Hz). Adrenaline (0.06 micrograms/kg/min) increased the rate of noradrenaline release into the plasma. This increase was prevented by propranolol (0.2 mg/kg + 0.1 mg/kg/h) and probably involves activation of presynaptic beta-adrenoceptors. A higher dose of adrenaline (1.0 micrograms/kg/min) significantly reduced the noradrenaline release rate. The reduction was "reversed" to a facilitatory effect by phenoxybenzamine (4 mg/kg). Propranolol alone slightly inhibited the noradrenaline release rate. After pretreatment with desipramine (1.0 mg/kg + 0.2 mg/kg/h), the inhibitory effect of propranolol on noradrenaline release was more pronounced and blood pressure was also lowered. However, in rabbits pretreated with captopril (1 mg/kg) in addition to desipramine, the sympathoinhibitory effect of propranolol was not observed. These results suggest that adrenaline can activate either presynaptic beta-adrenoceptors to increase noradrenaline release or, in higher doses, presynaptic alpha-adrenoceptors to inhibit noradrenaline release in vivo. The decrease in the noradrenaline release rate produced by propranolol alone may not be due to blockade of facilitatory presynaptic beta-adrenoceptors, but rather to depression of renin secretion. This would decrease angiotensin II formation and hence decrease the presynaptic release-enhancing effect of angiotensin II.     

Effect of ovarian steroids on uptake of radioactive amino acids by brain tissues

Effects of two major ovarian hormones, estrogen (E) and progesterone (P), on the uptake of amino acids by the brain nuclei of ovariectomized mice were examined. They were divided into four groups: (1) oil controls, (2) P-treated, (3) estradiol benzoate (E2B)-treated, and (4) E2B-primed P-treated mice. Two hr after the last hormonal treatment they were given a single s.c. injection of a mixture of 3H-leucine and 3H-methionine, and then sacrificed 2 hr later. Intensity of the uptake of radioactivity was measured on autoradiograms of the stained tissue sections. Group 1 showed a relatively high uptake of radioactivity by the SO, PV and SPH, compared with that by the remaining brain cells. Group 2 had a slight enhancement of the uptake by the VM, SPH and CC, compared with that in group 1. Group 3 showed a significant enhancement of the uptake by most of the preoptico-hypothalamic nuclei except for the VM, DM and PM, compared with that in group 1. Group 4 had slightly enhanced uptake by the POM, POL, SCH, SO, PV, VM, ARC, SPH and CC, compared with that in group 1. E-priming affected the uptake; it enhanced the uptake by the VM and SPH, and inhibited it by the PVA, AH, LH and CC. Uptake by the PM and EC remained unchanged in all groups. The present results suggest that two major steroids, E and P, influence protein synthesis in most of the brain regions including the preoptic and hypothalamic areas.(ABSTRACT TRUNCATED AT 250 WORDS)