The role of energy metabolism in calcium-evoked secretion from the adrenal medulla

1. Experiments were carried out on cat adrenal glands perfused with Locke solution to study the effects of inhibition of metabolism on calcium-evoked catecholamine release.2. In the presence of sodium cyanide (CN, 0.2 mM), a low concentration of glucose (1 mM) prevented the gradual decline in the secretory response to sequential exposures to calcium. Furthermore, when the secretory response was almost completely blocked by perfusing with a glucose-deprived solution containing CN, restoration of secretion was correlated with the glucose concentration in the perfusion medium.3. In the presence of CN, 2-deoxyglucose blocked both the protective effect and the restorative effect of glucose. The deoxyglucose inhibition of the glucose-dependent restoration of secretion was antagonized by a higher concentration of glucose.4. Restoration of calcium-evoked secretion was also observed after the washout of CN. The extent of this restoration was not at all related to the glucose concentration and was not affected by various inhibitors of carbohydrate metabolism, including deoxyglucose.5. Analysis of adrenal glands which had been perfused first with a glucose-free solution containing CN and subsequently with the normal medium indicated that no discernible synthesis of catecholamines had taken place during the experimental procedures.6. The data provide further evidence that the action of calcium to trigger medullary secretion requires the presence of metabolic energy and support the hypothesis that an interaction between calcium and high-energy nucleotides is a step in the sequence of events leading to the extrusion of catecholamines from the chromaffin cell.     

Simultaneous secretion of catecholamines from the adrenal medulla and of [3H]norepinephrine from sympathetic nerves from a single test preparation: different effects of agents on the secretion

The uptake and release of catecholamines was investigated in the isolated perfused adrenal gland of the rat after preloading the preparation with [3H]norepinephrine, and the effects of various agents were examined on the stimulation-evoked secretion of catecholamines and total tritium. Large quantities of tritium were found in the adrenal medulla after either intravenous injection of [3H]norepinephrine to the rat, or perfusion of the isolated adrenal gland with Krebs-bicarbonate solution containing [3H]norepinephrine. The retention of the tritium was inhibited 90% by desipramine. Acute treatment with guanethidine and chronic treatment with 6-hydroxydopamine abolished the secretion of tritium without affecting the secretion of catecholamines evoked at 1 Hz. Nicotine, muscarine and acetylcholine enhanced the secretion of catecholamines but not tritium, whereas tyramine and ephedrine enhanced the secretion of tritium but not catecholamines. It is concluded that chromaffin cells do not possess the norepinephrine uptake mechanism and that the uptake of [3H]norepinephrine occurs mainly in sympathetic nerve terminals present in the adrenal gland and the surrounding blood vessels (adrenal and renal veins). The differential localization of [3H]norepinephrine and catecholamines allowed us to test the effects of a variety of pharmacological agents that alter neurotransmitter release by acting on receptors on the neuronal membrane, acting on sodium and potassium channels, or acting to alter the intracellular concentrations of adenosine 3',5'-cyclic monophosphate and protein kinase C. Transmural stimulation (1 Hz for a total of 300 pulses) markedly enhanced the release of catecholamines and tritium which was blocked by tetrodotoxin (sodium channel-blocker) and potentiated by tetraethylammonium and gallamine (potassium channel-blockers). Phentolamine, an alpha adrenergic blocking agent which acts on both alpha-1 and alpha-2 receptors, caused a 3- to 4-fold facilitation of the tritium secretion while inhibiting catecholamine secretion by 45%. [Met]enkephalin almost completely inhibited the evoked-secretion of tritium but had very little effect on the secretion of catecholamines. Forskolin inhibited the tritium secretion by 80% but produced more than a 2-fold facilitation of catecholamine secretion. Phorbol 12,13-dibutyrate caused facilitation of evoked secretion of both catecholamines and tritium. A combination of phorbol ester and forskolin had a synergistic effect on stimulation-evoked secretion of catecholamines, whereas phorbol ester partially reversed the inhibitory effects of forskolin on the tritium secretion.(ABSTRACT TRUNCATED AT 400 WORDS)     

Catecholamine secretion by the adrenal medulla of the foetal and new-born foal

1. The content and output of adrenaline and noradrenaline from the equine adrenal medulla has been investigated under different conditions in foetuses, foals and adult mares.2. In the foetus only small amounts of both amines were secreted in response to stimulation of the peripheral ends of the splanchnic nerves to the gland; during anoxia the adrenal discharge was far greater and was independent of any nervous mechanism.3. Whereas in the ruminant a direct adrenal response to low P(O2) is confined to the noradrenaline cells during foetal life only, the adrenal medulla of the foetal foal secreted both adrenaline and noradrenaline during asphyxia, and the direct response persisted for some days after birth. Noradrenaline was the amine predominantly released during asphyxia in the foetus.4. Catecholamine output from the equine adrenal medulla changed with age, in that there was a gradual increase in both the absolute and relative amount of adrenaline released, irrespective of the stimulus applied, although at any given stage of development a higher proportion of adrenaline was secreted in response to stimulation of the splanchnic nerves than during anoxia.5. The relative proportions of the two amines in the effluent blood bore little resemblance to those found in the glands, removed after prolonged asphyxia, in either foetuses or foals. Preliminary observations have indicated that more noradrenaline is present in the glands when the foetus remains relatively undisturbed within the uterus.6. The possible significance of the larger adrenal response to asphyxia in the foetal foal in comparison with other species is discussed in relation to the development of the innervation and the growth of the adrenal cortex.     

Somatostatin and substance P inhibit catecholamine secretion from isolated cells of guinea-pig adrenal medulla

Chromaffin cells isolated from guinea-pig adrenal glands secrete catecholamines in response to acetylcholine, nicotine, pilocarpine, veratridine, and high [K⁺]. Both substance P and somatostatin inhibit acetylcholine-induced catecholamine secretion. The maximal inhibition of acetylcholine-induced catecholamine secretion produced by substance P and by somatostatin is approximately 60%: the concentrations of the peptides required for half-maximal inhibition of secretion are approximately 0.8 and 2 μM. respectively. The maximal inhibition of catecholamine secretion produced by somatostatin and that caused by substance P are not additive. The effects of the peptides on secretion are readily reversible. Somatostatin and substance P also inhibit nicotine-induced catecholamine secretion, but they do not inhibit catecholamine secretion stimulated by pilocarpine, veratridine, or high [K⁺]. Thus, these peptides specifically inhibit catecholamine secretion linked to stimulation of nicotinic receptors. The inhibition of acetylcholine-induced catecholamine secretion by somatostatin is noncompetitive with respect to acetylcholine, Na⁺ or Ca²⁺.Immunoreactive somatostatin and substance P are present in guinea-pig adrenal glands. It is suggested that these peptides may play a role in the regulation of catecholamine secretion from the adrenal medulla.     

Diseases of the adrenal medulla

The adrenal glands are vital in the organism's response to environmental stress. The outer cortex releases steroid hormones: glucocorticoids, mineralocorticoids and sex hormones, which are crucial to metabolism, inflammatory reactions and fluid homeostasis. The medulla is different developmentally, functionally and structurally. It co-releases catecholamines (primarily adrenaline and to some extent noradrenaline) as well as peptides by the all-or-none process of exocytosis from chromaffin granules, to aid in blood pressure and blood flow regulation, with regulated increments during the activation of the sympathetic nervous system. The co-released peptides function to regulate catecholamine release, blood vessel contraction and innate immune responses. Pathology within the adrenal medulla and the autonomic nervous system is primarily because of neoplasms. The most common tumour, called phaeochromocytoma when located in the adrenal medulla, originates from chromaffin cells and excretes catecholamines, but may be referred to as secreting paragangliomas when found in extra-adrenal chromaffin cells. Neoplasms, such as neuroblastomas and ganglioneuromas, may also be of neuronal lineage. We will also briefly discuss the catecholamine deficiency state.     

Isolation and characterization of myosin from the adrenal medulla

A protein with adenosine triphosphatase activity was isolated from bovine adrenal medulla and subsequently purified by ammonium sulfate precipitation and agarose gel filtration using a discontinuous two-buffer system. Characterization of this protein by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate, by assay of the activity of Ca2+, K(+)-EDTA and Mg2+ dependent adenosine triphosphatases by amino acid analysis and by electron microscopy has shown that the adrenal medullary myosin closely resembles those myosins isolated from muscle and other non-muscle cells. The possible roles of myosin in the adrenal medulla are discussed.     

The metabolic requirements from catecholamine release from the adrenal medulla

1. The metabolic requirements for catecholamine secretion elicited by acetylcholine or by calcium plus high K(+) were studied on acutely denervated perfused cat adrenal glands.2. Glucose-deprivation plus anoxia caused an increase in the spontaneous catecholamine output from adrenal glands perfused with normal Locke solution, which was abolished by the removal of calcium from the perfusion medium.3. Anoxia plus glucose-deprivation did not depress the secretory response to repeated exposures of a low concentration of acetylcholine, but did depress the response to a higher concentration of acetylcholine. Glucose-deprivation and nitrogen, when imposed either separately or together, did not inhibit total catecholamine output in response to calcium. Differential analysis of the calcium-evoked secretion showed that during anoxia, catecholamine output was maintained primarily by adrenaline secretion.4. Cyanide (0.2 mM) potentiated the secretory response to calcium in the presence of glucose, but when glucose was omitted from the perfusion medium, cyanide caused a gradual decline in calcium-evoked secretion. Iodoacetic acid (IAA) (0.2 mM) depressed the response to calcium by about 50% under aerobic conditions and by 90% under anaerobic conditions.5. The glycogen content of medullae was profoundly depleted under anoxic conditions.6. It is concluded that energy is required for the secretory action of calcium on medullary chromaffin cells. The energy may be derived from glycolysis or oxidative metabolism. A possible interaction between calcium and adenosine triphosphate acid (ATP) in eliciting catecholamine secretion is discussed.7. The alteration in the percent adrenaline and noradrenaline secreted during anoxia indicates that anoxia may regulate medullary catecholamine secretion through a peripheral, as well as a central mechanism.     

A method for determining the effect of certain drugs on the motor reaction of animals

Summary A method is described for quantiative determination of the motor reaction of experimental animals to pain stimulation with the aid of a simple apparatus. The latter consists of a wooden wheel, on the axis of which a tachometer is located. A cage with a mouse is mounted over the wheel. The electrode hooks were connected by means of a fine conductor with an induction coil. When electric stimulation is applied, the animal tries to escape and so it turns the wheel of the tachometer. Stimulation with an automatic electrode is conducted according to the chosen scheme, every 2 or 5 sec for one or more minutes. From the number of revolutions for a definite period of time, prior to and after the use of the substance investigated, a conclusion may be drawn on the effect produced.(Presented by Active Member AMN SSSR V. V. Parin) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 54, No. 8, pp. 116–118, August, 1962     

Oncocytoma of the adrenal gland medulla

We report an unprecedented case of an oncocytoma of the adrenal gland medulla in a 61-year-old woman. The patient presented with right flank pain and hematuria. Computed tomographic studies revealed a right adrenal gland mass that measured 2 cm, which was subsequently excised laparoscopically. Grossly, the tumor in the medulla measured 1.9 × 1.2 cm, weighed 5 g, and had a solid tan-brown cut surface. Histologically, it consisted of large tumor cells containing eosinophilic granular cytoplasm arranged in trabecular and nodular patterns. Electron microscopy revealed closely packed mitochondria in the cytoplasm of almost all tumor cells. The tumor cells were immunohistochemically positive for vimentin. The patient resumed usual activities 2 weeks after surgery, and at 6-month follow-up, she is doing well.