Morphometric and biochemical analysis of adrenal medullary hyperplasia induced by nicotine in rats

The administration of nicotine (1 and 4 mg/kg/day, subcutaneously for up to 6 weeks) to male Sprague-Dawley rats first induced a time-and dose-dependent increase in catecholamine (CA) synthesis. This was followed by an increase in endogenous CA levels and in total volume and number of chromaffin cells, as measured by stereological methods on serially sectioned adrenal glands. Thus, continued stimulation of the sympathoadrenal system generated an increase in biosynthetic enzyme activity, and subsequently adrenal medullary hypertrophy and hyperplasia developed as an adaptive reaction. The proposed model is useful for quantifying both biochemically and morphometrically early adrenal changes long before irreversible pathologic alterations are manifested.     

Vitamin D3-induced proliferative lesions in the rat adrenal medulla

Adrenal medullary hyperplasia and pheochromocytomas are induced in rats by a variety of non-genotoxic agents, and we have hypothesized that these agents induce lesions indirectly by stimulating chromaffin cell proliferation. Vitamin D3, which has not been previously associated with adrenal medullary proliferative lesions, is the most potent in vivo stimulus to chromaffin cell proliferation yet identified. The present investigation utilized the vitamin D3 model to prospectively test the relationship between mitogenicity and focal proliferative lesions in the adrenal medulla and to determine early events in the pathogenesis of these lesions. Charles River Crl:CD BR rats were treated with 0; 5000; 10,000; or 20,000 IU/kg/day of vitamin D3 in corn oil (5 ml/kg) by oral intubation. Rats were killed after 4, 8, 12, or 26 weeks of treatment, following a final week of labeling with bromodeoxyuridine (BrdU) using a mini-pump. Adrenal sections were double-stained for BrdU and phenylethanolamine-N-methyl transferase (PNMT) to discriminate epinephrine (E) from norepinephrine (NE) cells or for vesicular acetylcholine transporter (VAchT) to identify cholinergic nerve endings. Vitamin D3 caused a 4-5-fold increase in BrdU labeling at week 4, diminishing to a 2-fold increase by week 26. An initial preponderance of labeled E cells gave way to a preponderance of labeled NE cells. By week 26, 17/19 (89%) animals receiving the 2 highest doses of vitamin D3 had focal adrenal medullary proliferative lesions, in contrast to an absence of lesions in control rats. The lesions encompassed a spectrum including BrdU-labeled "hot spots" not readily visible on H and E sections, hyperplastic nodules, and pheochromocytomas. Lesions were usually multicentric, bilateral, and peripheral in location, and almost all were PNMT-negative. The lesions were not cholinergically innervated, suggesting autonomous proliferation. Hot spots, hyperplastic nodules, and pheochromocytomas appear to represent a continuum rather than separate entities. Their development might involve selective responses of chromaffin cell subsets to mitogenic signals, influenced by both innervation and corticomedullary interactions. A number of non-genotoxic compounds that induce pheochromocytomas in rats are known to affect calcium homeostasis. The results of this study provide further evidence to support the hypothesis that altered calcium homeostasis is indirectly involved in the pathogenesis of pheochromocytomas, via effects on chromaffin cell proliferation.      

Effects of delta-9-tetrahydrocannabinol exposure on adrenal medullary function: evidence of an acute effect and development of tolerance in chronic treatments.

Previous studies have shown that the secretion of several stress-related hormones can be altered by exposure to marihuana or its purified constituents. The purpose of this study was to examine changes in adrenal medullary function caused by acute, subchronic and chronic treatments with two different doses of delta-9-tetrahydrocannabinol (THC). Acute exposure to THC caused a significant decrease in the adrenal medulla contents of both norepinephrine (NE) and epinephrine (E) and a significant increase in the E/NE ratio. These effects were mainly observed with the highest dose of THC, but they were not accompanied by a statistically significant decrease in adrenal medulla tyrosine hydroxylase activity, the rate-limiting enzyme in the catecholamine (CA) synthesis. These effects disappeared after seven or fourteen days of a daily THC treatment, which suggests the development of tolerance to this drug. Analysis of plasma PRL, ACTH and corticosterone levels showed some THC-related changes in these hormones. THC-induced modifications in ACTH and corticosterone were not in parallel to the changes in the adrenal medulla function, whereas those effects of acute THC on PRL release were statistically correlated with decreases of CA contents following acute THC. In conclusion, acute exposure to THC caused an alteration in the adrenal medullary function, reflected by a fall in endogenous stores of both CAs which could influence the adrenal medullary response to stress situations. This acute effect of THC could be mediated by the pituitary secretion of PRL, although the possibility of an effect directly exerted on the adrenal medulla chromaffin cells should be also considered.(ABSTRACT TRUNCATED AT 250 WORDS)     

All-or-none secretion of adrenal medullary storage vesicle contents in the rat

Rats were given insulin (5 i.u./kg) to produce hypoglycemia and a resultant sympathetic discharge and were sacrificed 1, 2, 3 and 4 hr after drug administration. Intact adrenal storage vesicles were separated from empty vesicles by differential and density gradient centrifugation, and all fractions were analyzed for catecholamines (CA), dopamine β-hydroxylase (DBO; a marker for vesicle membranes) and ATP. One hr after insulin, CA, DBO and ATP in the intact vesicles had fallen to 60 per cent of control, and after 2 hr, to 50 per cent of control. DBO, but not CA or ATP, increased in the empty vesicle fraction. After 3 hr, vesicular CA and ATP had fallen to 35 per cent of controls, while DBO fell only to 50 per cent; DBO remained elevated in the empty vesicle fraction. The parallel loss of CA, DBO and ATP from the intact vesicles during the early time periods, and the increase in particulate DBO in the empty vesicle fraction suggest that secretion from the rat adrenal medulla occurs by an exocytotic release of the total vesicle content with retention of the vesicle membrane, and that release of vesicle contents is all-or-none. The disparity between the loss of DBO and CA after prolonged stimulation has several possible explanations, among which may be the existence of a population of vesicles having DBO, but little or no CA or ATP, or the beginning of vesicle resynthesis. After insulin administration to another group of rats, the incorporation of epinephrine and metaraminol (MA) by isolated adrenal storage vesicles declined. After 1 hr, total adrenal CA had dropped to 68 per cent of control; epinephrine uptake per gland was 72 per cent, and MA uptake was 75 per cent. CA decreased progressively to 22 per cent of control after 4 hr; epinephrine uptake decreased similarly. MA uptake remained at about 70 per cent of control even after 4 hr. The parallel nature of CA depletion and decrease in epinephrine uptake also suggests that secretion from rat adrenal medullary vesicles is exocytotic and all-or-none. The absence of a parallel decrease in MA uptake may mean that MA is taken up into vesicles which do not have a normal CA content (“immature” vesicles). The existence of immature vesicles 3 hr after insulin administration suggests that the rate of vesicle turnover in the rat adrenal medulla is rapid.     

Endothelin regulation of adrenal function

1. The goal of the present review is to recount the evidence that endothelin (ET) has a significant influence on the peripheral sympathetic nervous system by regulating the function of the adrenal medulla. 2. The presence of an active ET system in the adrenal medulla has been clearly demonstrated. Endothelin protein, mRNA, binding sites and ET-converting enzyme have been identified in adrenal tissue and medullary chromaffin cells, suggesting that this peptide may contribute to the regulation of adrenal medullary function. 3. Studies investigating the function of ET in the adrenal gland have demonstrated that ET has a stimulatory effect on the adrenal medulla. Endothelin elicits an increase in catecholamine release from perfused intact adrenal glands as well as from cultured chromaffin cells. This effect has been shown to be mediated by ETA and ETB receptors. 4. The mechanism by which ET causes an increase in catecholamine release from the adrenal medulla appears to be independent of cholinergic activation of chromaffin cells. Endothelin has been shown to act directly at chromaffin cells to increase intracellular calcium, which results in catecholamine release. 5. Endothelin can indirectly affect catecholamine release by its effect on adrenal blood flow. Studies indicate that ET has both vasoconstrictor and vasodilator effects in the adrenal gland, which suggests a role for ET in the regulation of adrenal blood flow. Endothelin has also been proposed to participate in the selective contraction of the adrenomedullary veins, which enhances the discharge of catecholamines from the adrenal gland during activation.     

Influences of long-term administration of 24R, 25-dihydroxyvitamin D3, a vitamin D3 derivative, in rats.

In order to examine the influences by long-term feeding of 24R, 25 dihydroxyvitamin D3[24R, 25(OH)2D3], an active form of vitamin D, Wistar rats (14-week-old, male, 20 rats/group) were fed a powder diet containing 0 or 5 ppm 24R, 25(OH)2D3 for 57 weeks. Final body weights and total food consumption were comparable between the groups. Urinary calcium levels were significantly (p < 0.05 or 0.01) increased by the administration of 24R, 25(OH)2D3 at weeks 3, 22 and 56, although the levels of serum calcium did not differ between the groups at the termination of week 57. In the 24R, 25(OH)2D3 group, weights of the adrenals and femurs were significantly (p < 0.01) increased. Histopathologically, this was found due to thickening of cortical bone in the femurs, and medullary hyperplasia and pheochromocytoma of the adrenals. Immunohistochemically, proliferating cell nuclear antigen (PCNA)-labeling indices for intact adrenal medulla, medullary hyperplasia and pheochromocytoma in the 24R, 25(OH)2D3 group were respectively 1.82 +/- 1.21, 5.88 +/- 4.13 and 16, all higher than that for the adrenal medulla in the control group (0.87 +/- 0.67). These results indicate that 24R, 25(OH)2D3 at a dose with which serum calcium is not chronically increased causes thickening of the cortex of the femur, and development of adrenal proliferative lesions, suggesting that rats may be too sensitive for results to be relevant to human risk assessment.     

Increase in catecholamine release and 45Ca2+ uptake induced by GABA in cultured bovine adrenal chromaffin cells

The role of Ca2+ in GABA-evoked catecholamine (CA) release from adrenal medulla was investigated in primary cultures of bovine adrenal chromaffin cells. GABA facilitated the 45Ca2+ uptake associated with the increase of Ca release in cultured bovine adrenal chromaffin cells. The effects of GABA on both 45Ca2+ uptake and CA release were blocked by bicuculline and picrotoxin. Nifedipine reduced the 45Ca2+ uptake and CA release induced by GABA. These data support our previous suggestion that the activation of GABA receptors on adrenal chromaffin cells facilitates the Ca2+ influx through voltage-sensitive Ca2+ channels, leading to the release of CA.     

Effect of hypophysectomy on cAMP changes in rat adrenal medulla evoked by catecholamines and carbamylcholine

Summary It was the aim of this study to investigate the mechanisms responsible for changes in 3,5-cyclic adenosine monophosphate (cAMP) in the rat adrenal medulla occuring after administration of carbamylcholine, histamine, ACTH and various phenylethylamines.Carbamylcholine, ACTH, histamine, noradrenaline and dopamine produced marked (500–900%) increases in adrenal cAMP which were very similar in both adrenal cortex and medulla both with respect to time-course and relative extent. Interestingly isoprenaline and adrenaline did not influence cAMP levels even at excessively high doses. In all cases studied transsection of the splanchnic fibers supplying the adrenals reduced the increase in medullary cAMP by not more than 25–30%, suggesting that cAMP levels in the adrenal medulla are predominantly regulated by non-neuronal mechanisms. This assumption was strongly supported by the observation that hypophysectomy completely abolished the 500–600% increase in cAMP produced by 50 mol/kg of dopamine and reduced the 700% increase resulting from 4.4 mol/kg of carbamylcholine to 70%. In spite of the marked increase in cAMP produced by single and repeated doses of dopamine in the adrenal medulla there was no subsequent induction of tyrosine hydroxylase (TH). Moreover carbamylcholine (8.2 mol/kg) evoked TH induction only in innervated adrenals whereas after denervation, in spite of the large (+500%) and prolonged (more than 90 min) increase in cAMP, no TH induction could be observed.It is concluded that adrenal medullary cAMP is predominantly regulated by the pituitary gland via the adrenal cortex and only to a much smaller extent — if at all—by direct cholinergic mechanisms, which are responsible for the initiation of TH induction.     

Effect of apomorphine, piribedil and haloperidol on adrenal ornithine decarboxylase activity of the rat

The administration of the dopaminergic drugs, apomorphine and piribedil to rats resulted in an increase in the activity of ornithine decarboxylase of the adrenal medulla and cortex. Pretreatment of the rats with the dopamine-receptor antagonist haloperidol caused a partial blockade of the apomorphine-induced effect at 4 hr in both medulla and cortex. At 6 hr, however, haloperidol did not block the effect of apomorphine and produced an increase in ornithine decarboxylase activity of both structures when administered alone. Hypophysectomy abolished the cortical ornithine decarboxylase response to apomorphine and haloperidol and the medullary response to haloperidol. The results suggest that the response of cortical ornithine decarboxylase activity to apomorphine and haloperidol is entirely mediated by the hypophysis and that the effect of apomorphine and the antagonistic action of haloperidol towards apomorphine in regard to the induction of adrenal medullary ornithine decarboxylase must be taking place at some central site independent of the hypothalamic-hypophyseal system.     

Blockade of β-adrenoceptors restores the GRK2-mediated adrenal α(2) -adrenoceptor-catecholamine production axis in heart failure

BACKGROUND AND PURPOSE

Sympathetic nervous system (SNS) hyperactivity is characteristic of chronic heart failure (HF) and significantly worsens prognosis. The success of β-adrenoceptor antagonist (β-blockers) therapy in HF is primarily attributed to protection of the heart from the noxious effects of augmented catecholamine levels. β-Blockers have been shown to reduce SNS hyperactivity in HF, but the underlying molecular mechanisms are not understood. The GPCR kinase-2 (GRK2)–α₂adrenoceptor–catecholamine production axis is up-regulated in the adrenal medulla during HF causing α₂-adrenoceptor dysfunction and elevated catecholamine levels. Here, we sought to investigate if β-blocker treatment in HF could lower SNS activation by directly altering adrenal GRK2 levels.

EXPERIMENTAL APPROACH

Four weeks after myocardial infarction-induced HF, adult rats were randomized to 10-week treatment with vehicle (HF/C) or bisoprolol (HF/B). Cardiac function and dimensions were measured. In heart and adrenal gland, GRK2 levels were assessed by RT-PCR and Western blotting and adrenoceptors studied with radioligand binding. Catecholamines and α₂adrenoceptors in adrenal medulla chromaffin cell cultures were also measured.

KEY RESULTS

Bisoprolol treatment ameliorated HF-related adverse cardiac remodelling and reduced plasma catecholamine levels, compared with HF/C rats. Bisoprolol also attenuated adrenal GRK2 overexpression as observed in HF/C rats and increased α₂adrenoceptor density. In cultures of adrenal medulla chromaffin cells from all study groups, bisoprolol reversed HF-related α₂adrenoceptor dysfunction. This effect was reversed by GRK2 overexpression.

CONCLUSION AND IMPLICATIONS

Blockade of β-adrenoceptors normalized the adrenal α₂adrenoceptor-catecholamine production axis by reducing GRK2 levels. This effect may contribute significantly to the decrease of HF-related sympathetic overdrive by β−blockers.     

Activation of adrenal medulla adenylate cylase and catecholamine secretion

Summary The beta-adrenergic agonist, salbutamol, cAMP and theophylline induced secretion of catecholamines (CA) from rat adrenal medulla, incubated in vitro in calcium-free Locke's solution. Beta-adrenergic antagonists inhibited the CA secretion induced by betaadrenergic agonists. The beta₂-antagonist, H35/25, was more effective than the beta₁-antagonist, practolol. Salbutamol augmented the release of CA induced by ouabain or by K-free medium in the presence of calcium. Propranolol partially inhibited the release of CA induced under these conditions, as well as that caused by acetylcholine. Adenylate cyclase activity in a membrane preparation from bovine adrenal medulla was enhanced in decreasing order, by the following catecholamines: isoprenaline > salbutamol > adrenaline > dopamine > noradrenaline. Phenylephrine and tyramine had no effect. The activation of adrenal medullary adenylate cyclase was inhibited by beta-adrenergic antagonists: H 35/25 (a beta₂-antagonist) was more effective than practolol, a beta₁-antagonist. The concentrations of salbutamol and of beta-adrenergic antagonists which activated and blocked, respectively, adenylate cyclase, fit the doses which increased and inhibited, respectively, CA secretion from adrenal medulla in vitro. It is suggested that beta-adrenergic stimulation in the adrenal medulla enhances CA release through an increase of cAMP and that this mechanism may be effective under conditions of intensive physiological stimulation in vivo. Other functions (synthesis of CA, synthesis of tyrosine hydroxylase) may depend on activation of adenylate cyclase in adrenal medulla by beta-adrenoceptors.     

Polyphenols of Rubus coreanum Inhibit Catecholamine Secretion from the Perfused Adrenal Medulla of SHRs

The present study was attempted to investigate whether polyphenolic compounds isolated from wine, which is brewed from Rubus coreanum Miquel (PCRC), may affect the release of catecholamines (CA) from the isolated perfused adrenal medulla of the spontaneously hypertensive rats (SHRs), and to establish its mechanism of action. PCRC (20~180 µg/ml) perfused into an adrenal vein for 90 min relatively dose-dependently inhibited the CA secretory responses to ACh (5.32 mM), high K⁺ (56 mM), DMPP (100 µM) and McN-A-343 (100 µM). PCRC itself did not affect basal CA secretion (data not shown). Also, in the presence of PCRC (60 µg/ml), the CA secretory responses to veratridine (a selective Na⁺ channel activator (10 µM), Bay-K-8644 (a L-type dihydropyridine Ca²⁺ channel activator, 10 µM), and cyclopiazonic acid (a cytoplasmic Ca²⁺ -ATPase inhibitor, 10 µM) were significantly reduced, respectively. In the simultaneous presence of PCRC (60 µg/ml) and L-NAME (an inhibitor of NO synthase, 30 µM), the inhibitory responses of PCRC on the CA secretion evoked by ACh, high K⁺, DMPP, and Bay-K-8644 were considerably recovered to the extent of the corresponding control secretion compared with that of PCRC-treatment alone. The level of NO released from adrenal medulla after the treatment of PCRC (60 µg/ml) was greatly elevated compared with the corresponding basal level. Taken together, these results demonstrate that PCRC inhibits the CA secretion from the isolated perfused adrenal medulla of the SHRs evoked by stimulation of cholinergic receptors as well as by direct membrane-depolarization. It seems that this inhibitory effect of PCRC is mediated by blocking the influx of calcium and sodium into the adrenal medullary chromaffin cells of the SHRs as well as by inhibition of Ca²⁺ release from the cytoplasmic calcium store at least partly through the increased NO production due to the activation of NO synthase.     

Effect of 2,4,6-trinitrophenol on catecholamine secretion from perfused bovine adrenal glands

2,4,6-Trinitrophenol (PA) evoked a prolonged catecholamine (CA) secretion from perfused bovine adrenal glands. The PA-evoked CA secretion was concentration-dependent, required the presence of extracellular calcium and resulted from a direct action of PA on the chromaffin cells. Furthermore, PA reduced Mg2+-ATPase activities in the plasma membrane-rich microsome and granule-rich fraction from the adrenal medulla. These results indicate that PA evokes CA secretion through the actions on both the chromaffin cell membranes and granule membranes.     

Further evidence for a cAMP dependent regulation of tyrosine-3-monoxygenase induction in adrenal medulla

Summary Unilateral adrenal denervation caused a gradual decrease of adenylate cyclase activity in rat adrenal medulla. The extent of the increase in adrenal medullary 3,5-cyclic adenosine monophosphate (cAMP) content elicited by injections of carbamylcholine declined gradually following adrenal denervation. Three or nine days after denervation carbamylcholine caused rise of cAMP and a delayed increase of tyrosine-3-mono-oxygenase (TH) activity of similar magnitude in intact and denervated adrenal medullae. However, after an interval of 15 days or longer following denervation the increase in TH activity elicited by carbamylcholine was greatly reduced. These results support previous proposals that cAMP is involved as a second messenger in the trans-synaptic induction of TH.     

Mechanism of PGE inhibition of catecholamine release from adrenal medulla.

Catecholamine (CA) secretion from the adrenal medulla was induced in vitro by acetylcholine (10(-4)M) (ACh), by incubation in potassium-free medium, by addition of ouabain (10(-3)M), by theophylline (10(-2)M) or by salbutamol (10(-6) and 6 x 10(-6) M). Theophylline and salbutamol, but not ACh, released CA in a calcium-free medium supplemented with 2mM EGTA. PGE2 significantly inhibited both CA secretion evoked by ACh and that evoked by salbutamol, i.e. both secretion dependent on, and independent of, extracellular calcium, PGE2 counteracted the increase of cAMP levels caused by ACh or salbutamol in adrenal medullary slices. PGE2 also diminished the salbutamol-induced activation of adenylate cyclase in an adrenal medullary membrane preparation, PGE2 reduced the rate of 45Ca efflux from slices of adrenal medulla preloaded with 45CaCl2. It is suggested that PGE2 inhibits CA secretion through the following sequence: inhibition of adenylate cyclase, a fall of cellular cAMP resulting in reduced release of calcium from intracellular binding sites and reduced free cytoplasmic calcium.     

Involvement of 3′,5′-cyclic adenosine monophosphate in the increase of tyrosine hydroxylase activity elicited by cold exposure

Summary We studied the relationship between changes of 3,5-cyclic adenosine monophosphate (cAMP) and tyrosine hydroxylase (TH) activity in adrenal medulla of rats exposed to cold stress. Exposure of rats to 4° C produced a ten-fold increase of the cAMP content of adrenal medulla in about 30 min. This increase persisted for about one hour; the levels of cAMP returned to control value within 120 min in spite of the continued exposure to 4° C. In rats with monolaterally denervated (splanchnicotomized) adrenal, the exposure to 4° C produced only insignificant changes of cAMP concentration. During the exposure to 4° C we also observed an increase (about two times) of catecholamine turnover rate as measured by ³H-dopamine efflux from adrenal glands. This increased efflux persisted for 6 h of exposure to cold suggesting that the efflux of ³H-dopamine can increase without a simultaneous increase of cAMP concentrations. Exposure of rats to 4° C for two hour also increases (about two times) the TH activity as measured 24 h later. Exposure of the animals to 4° C for a time period longer than two hour (4 or 24 h) failed to produce further increases of TH activity. These results support the concept that the increase of cAMP concentrations in adrenal medulla may play a central role in initiating the chain of biochemical events modulating the synthesis of TH.     

Evidence against a causal relationship between increase in c-AMP and induction of tyrosine hydroxylase in the rat adrenal medulla

Summary It was the purpose of the present experiments to establish whether the reserpine-mediated changes in adrenomedullary c-AMP result from - or -adrenergic activation of adenylate cyclase by catecholamines liberated from adrenal chromaffin cells and whether a causal relationship exists between these changes and subsequent induction of tyrosine hydroxylase (TH).The reserpine-mediated increase in c-AMP was blocked by neither - nor -adrenergic blocking agents. However, propranolol abolished the increase in c-AMP by a mechanism which is not related to the -blocking properties of this drug. Although propranolol abolished the reserpine-mediated increase in c-AMP it did not interfere with the subsequent TH induction. Moreover, administration of aminophylline together with reserpine produced a larger and more prolonged increase in c-AMP in denervated adrenals than reserpine alone in intact glands. Denervation prevented TH induction in spite of the more extensive increase in c-AMP in the adrenal medulla after the combined treatment. It is concluded that there is no causal relationship between the overall increase in c-AMP in the adrenal medulla and the subsequent TH induction. However, the possibility that a small pool of c-AMP which is overshadowed by the non-related overall changes may be involved in trans-synaptic TH induction cannot be excluded.     

GABAA receptor sites modulating catecholamine secretion in the rat adrenal gland: evidence from 3H-muscimol autoradiography and in vivo functional studies

The occurrence and distribution of specific 3H-muscimol binding sites, most probably identical with A type gamma-aminobutyric acid (GABA) receptors, were studied in sections of the rat adrenal gland by light microscope autoradiography. Specific binding was found primarily in the adrenal medulla, in association with chromaffin cells. A limited number of binding sites was also observed within the adrenal cortex. In urethane-anaesthetized hexamethonium-pretreated rats, intravenous GABA produced a set of 'excitatory' cardiovascular effects (increase in heart rate, force of contraction and blood pressure) which were mimicked by intravenous muscimol but not by intravenous baclofen, and were antagonized by pretreatment with bicuculline. The cardiovascular excitatory effects of intravenous GABA were unaffected by reserpine pretreatment, markedly reduced by administration of phentolamine plus propranolol, and almost completely abolished by adrenalectomy. Our findings indicate the presence of GABA receptor sites on adrenal chromaffin cells, whose excitation can produce changes in cardiovascular function.     

Bovine chromaffin cell cultures as model to study organophosporus neurotoxicity

Based on the high level of phenyl valerate esterase activities, and in particular of neuropathy target esterase (NTE) found in bovine adrenal medulla, chromaffin cells culture have been proposed as an alternative model for the study of organophosphorus neurotoxicity. Organophosphorus-induced polyneuropathy is a syndrome related to the inhibition and further modification by organophosphorus compounds of NTE (a protein that displays phenyl valerate esterase activity resistant to mipafox and sensitive to paraoxon). Total phenyl valerate esterase activities found in homogenate, particulate and soluble fractions of bovine adrenal medulla were 5200+/-35, 5000+/-280 and 1700+/-260 mU/g tissue, respectively. Cultured chromaffin cells displayed a total hydrolysing activity of 41+/-5 mU/10(6) cells. Homogenates of bovine adrenal medulla displayed only about 6% of activity sensitive to paraoxon. Most of the phenyl valerate esterase activity inhibited by mipafox (a neuropathy inducing compound) was found in particulate fraction. Cultured chromaffin cells displayed kinetics of inhibition by mipafox similar to the kinetics displayed by homogenates of bovine adrenal medulla. We conclude that NTE could be assayed in this system by only using one inhibitor (mipafox) instead of two (paraoxon and mipafox). Also, the proposal is supported of using chromaffin cells as in vitro model for the study of the role of NTE and related esterases in organophosphorus-induced polyneuropathy.     

儿茶酚胺症(附12例报告)

１２例儿茶酚胺症均经病理及手术证实,其中１０例为肾上腺嗜铬细胞瘤（ＡＭＰ）,１例肾上腺髓质增生（ＡＭＨ）,１例恶性嗜铬细胞瘤。ＣＡ和ＶＭＡ测定对诊断有特异性,ＡＭＨ的诊断依赖于病理,对于无高血压症状的嗜铬细胞瘤,认为采用“静止嗜铬细胞瘤”为妥,手术是治疗儿茶酚胺症的根本治疗方法,充分的术前准备是重要的。