Physiology
Stephen W. Carmichael, Susan L. Stoddard in The Adrenal Medulla 1986 - 1988, 2017
Catecholamines secreted from the adrenal medulla are involved in the mediation of most physiologic processes. Plasma norepinephrine levels were decreased to half after both demedullation and sympathectomy, suggesting that paraganglia in the sheep provides some contribution to the resting levels of catecholamines. Increased sympathoadrenal activity is the primary autonomic response that occurs during exercise. The nonshivering thermogenesis that develops with prolonged cold exposure is stimulated in a nonlinear fashion by the infusion of norepinephrine. Lymphatic transport of norepinephrine was related quadratically to the infusion rate, indicating a similar relationship between infusion rate and influx of norepinephrine into the extravascular space. Intravenous injection of nicotine inhibited the gastric acid output elicited by stimulation of the vagus nerve and initially inhibited gastric mucosal blood flow; these effects were blocked by phentolamine or by adrenalectomy plus reserpine. Gastric acid secretion may be modulated by central mechanisms.
Adrenal Medulla
Paul V. Malven in Mammalian Neuroendocrinology, 2019
The chromaffin cells of the adrenal medulla are innervated neuroendocrine cells that secrete catecholaminergic neurohormones into the blood. The biosynthetic steps leading to norepinephrine occur in all the chromaffin cells of the adrenal medulla. In mammals, the phenylethanolamine N-methyl transferase (PNMT) enzyme is almost exclusively localized in the adrenal medulla with only small quantities in the brain and in the sympathetic nerves of the heart. The subset of chromaffin cells that contain PNMT and synthesize epinephrine are regionally localized in a species-specific manner. The primary secretory products of adrenal medullary cells are the catecholamines, norepinephrine and epinephrine. In the discussion on biological actions of catecholamines, the induced breakdown of glycogen to yield glucose was one important action that could only be accomplished by adrenomedullary secretions. Therefore, low blood glucose represents one of the most important provocative stimuli of such secretion.
The Adrenal Medulla: Physiology and Pathophysiology
Liana Bolis, Julio Licinio, Stefano Govoni in Handbook of the Autonomic Nervous System in Health and Disease, 2002
A. Functions of the Adrenal Medulla Epinephrine was first isolated and identified as the principal secretory product of the adrenal medulla at the turn of the twentieth century by Takamine (1). The concept of the sympathoadrenal system as a single functional unit stems largely from the studies by Walter Cannon of epinephrine as the primary mediator of the fightor-flight response (2). Although norepinephrine, not epinephrine, was subsequently identified as the principal transmitter secreted by sympathetic nerves (3), the concept of the sympathoadrenal system as a single functional unit persisted. It is now becoming increasingly clear, however, that the sympathoneural and adrenal medullary systems are regulated separately and often in divergent directions in response to different forms of stress (4). This and the many functional differences between the two systems make their separate consideration and comparison appropriate.
The Use of Epinephrine for Out-of-Hospital Treatment of Anaphylaxis: Resource Document for the National Association of EMS Physicians Position Statement
Published in Prehospital Emergency Care, 2011
Ryan C. Jacobsen, Michael G. Millin
Anaphylaxis is a potentially life-threatening condition that requires both prompt recognition and treatment with epinephrine. All levels of emergency medical services (EMS) providers, with appropriate physician oversight, should be able to carry and properly administer epinephrine safely when caring for patients with anaphylaxis. EMS systems and EMS medical directors should develop a mechanism to review the charts of patients who received epinephrine and were not in cardiac arrest. This will help to ensure the safe and appropriate use of epinephrine in order to provide continued quality improvement. Despite the safety of epinephrine, EMS systems that carry epinephrine autoinjectors should establish protocols to deal with patients or emergency responders who have an unintentional injection of epinephrine into the hand or digit. Continued research is needed to better define the role that EMS plays in the management of anaphylaxis. This paper serves as a resource document to the National Association of EMS Physician position on the use of epinephrine for the out-of-hospital treatment of anaphylaxis. Key words: EMS; prehospital; anaphylaxis; epinephrine; intramuscular epinephrine
Impaired responsiveness of platelets to epinephrine due to α2A adrenoreceptor deficiency in Male Chinese
Published in Platelets, 2016
Tsun-Mei Lin, Jih-Shyan Lin, Jen-Yu Tseng, Shang-Yin Wu, Tsai-Yun Chen
Epinephrine is known as a weak, but important, agonist for platelet activation. It has been reported that the responsiveness of platelets to epinephrine was markedly impaired in 6% of Caucasians and in 16% of Japanese. The purpose of this study was to screen and characterize this abnormality in healthy Taiwanese Chinese volunteers. We used aggregometry, flow cytometry and platelet function analyzer (PFA)-100 system to assess in 50 healthy male volunteers the responsiveness of platelets to epinephrine stimulation. Using α2A adrenoceptor antagonist BRL44408 maleate competition and a [3H]yohimbin binding assay, we evaluated α2A adrenoceptors on platelets. The aggregation of platelets after stimulation with 10 μM of epinephrine indicated two distinct groups of study participants: 24 (48.0%) good- and 26 (52.0%) impaired-responders to epinephrine. Flow cytometric analysis of platelets after stimulated with 1 μM epinephrine showed that glycoprotein (GP) IIb/IIIa and P-selectin expression of epinephrine good- and impaired-responders were 27.1 ± 11.0% vs. 9.9 ± 5.4% (p = 0.003) and 12.2 ± 6.2% vs. 3.6 ± 3.5% (p < 0.001), respectively. The PFA-100 system showed that epinephrine-impaired-responders had a longer collagen-epinephrine induced closure time. Good-responder platelets incubated with BRL44408 maleate had an impaired response to epinephrine stimulation. [3H]yohimbine binding studies showed fewer α2A adrenoreceptors on the platelets of epinephrine-impaired-responders than on those of good-responders. The prevalence of impaired responsiveness to epinephrine was high and probably due to α2A adrenoreceptor deficiency in male Taiwanese Chinese.
NANO-GOLD MODIFIED GLASSY CARBON ELECTRODE FOR SELECTIVE DETERMINATION OF EPINEPHRINE IN THE PRESENCE OF ASCORBIC ACID
Published in Analytical Letters, 2002
ABSTRACT The nano-gold modified glassy carbon electrode, which can catalytically oxidize and accumulate epinephrine was obtained by electrodeposition. The effect of pH value and concentration of phosphate buffer solution (PBS) on the electrochemical behavior of epinephrine was studied. Two separating oxidation peaks of epinephrine and ascorbic acid can be observed at the nano-gold modified glassy carbon electrode in cyclic voltammogram. So it can be applied for determination of epinephrine in the presence of ascorbic acid. The peak current of epinephrine is in linear relationship with its concentration in the range of 1.0 × 10−4–1.0 × 10−6 M. Furthermore, the FT-IR spectrometry was employed to study the oxidation of epinephrine.