1
|
Nørgaard S, Joyce W, Jensen MF, Enok S, Skovgaard N, Wang T. Histamine exerts both direct H 2-mediated and indirect catecholaminergic effects on heart rate in pythons. J Comp Physiol B 2021; 191:347-355. [PMID: 33474644 DOI: 10.1007/s00360-020-01338-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 12/22/2020] [Accepted: 12/30/2020] [Indexed: 11/25/2022]
Abstract
The vertebrate heart is regulated by excitatory adrenergic and inhibitory cholinergic innervations, as well as non-adrenergic non-cholinergic (NANC) factors that may be circulating in the blood or released from the autonomic nerves. As an example of NANC signaling, an increased histaminergic tone, acting through stimulation of H2 receptors, contributes markedly to the rise in heart rate during digestion in pythons. In addition to the direct effects of histamine, it is also known that histamine can reinforce the cholinergic and adrenergic signaling. Thus, to further our understanding of the histaminergic regulation of the cardiovascular response in pythons, we designed a series of in vivo experiments complemented by in vitro experiments on sinoatrial and vascular ring preparations. We demonstrate the tachycardic mechanism of histamine works partly through a direct binding of cardiac H2 receptors and in part through a myocardial histamine-induced catecholamine release, which strengthens the sympathetic adrenergic signaling pathway.
Collapse
Affiliation(s)
- Simon Nørgaard
- Department of Biology, Aarhus University, C.F. Møllers Allé 3, building 1131, 8000, Aarhus C, Denmark
| | - William Joyce
- Department of Biology, Aarhus University, C.F. Møllers Allé 3, building 1131, 8000, Aarhus C, Denmark
| | - Maja Fuhlendorff Jensen
- Department of Biology, Aarhus University, C.F. Møllers Allé 3, building 1131, 8000, Aarhus C, Denmark
| | - Sanne Enok
- Department of Biology, Aarhus University, C.F. Møllers Allé 3, building 1131, 8000, Aarhus C, Denmark
| | - Nini Skovgaard
- Department of Biology, Aarhus University, C.F. Møllers Allé 3, building 1131, 8000, Aarhus C, Denmark
| | - Tobias Wang
- Department of Biology, Aarhus University, C.F. Møllers Allé 3, building 1131, 8000, Aarhus C, Denmark.
| |
Collapse
|
2
|
Enok S, Leite GSPC, Leite CAC, Gesser H, Hedrick MS, Wang T. Improved cardiac filling facilitates the postprandial elevation of stroke volume in Python regius. ACTA ACUST UNITED AC 2016; 219:3009-3018. [PMID: 27445352 DOI: 10.1242/jeb.142729] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 07/18/2016] [Indexed: 01/10/2023]
Abstract
To accommodate the pronounced metabolic response to digestion, pythons increase heart rate and elevate stroke volume, where the latter has been ascribed to a massive and fast cardiac hypertrophy. However, numerous recent studies show that heart mass rarely increases, even upon ingestion of large meals, and we therefore explored the possibility that a rise in mean circulatory filling pressure (MCFP) serves to elevate venous pressure and cardiac filling during digestion. To this end, we measured blood flows and pressures in anaesthetized Python regius The anaesthetized snakes exhibited the archetypal tachycardia as well as a rise in both venous pressure and MCFP that fully account for the approximate doubling of stroke volume. There was no rise in blood volume and the elevated MCFP must therefore stem from increased vascular tone, possibly by means of increased sympathetic tone on the veins. Furthermore, although both venous pressure and MCFP increased during volume loading, there was no evidence that postprandial hearts were endowed with an additional capacity to elevate stroke volume. In vitro measurements of force development of paced ventricular strips also failed to reveal signs of increased contractility, but the postprandial hearts had higher activities of cytochrome oxidase and pyruvate kinase, which probably serves to sustain the rise in cardiac work during digestion.
Collapse
Affiliation(s)
- Sanne Enok
- Zoophysiology, Department of Bioscience, Aarhus University, Aarhus 8000, Denmark
| | - Gabriella S P C Leite
- Department of Physiological Sciences, Federal University of São Carlos, São Paulo 13565-905, Brazil
| | - Cléo A C Leite
- Department of Physiological Sciences, Federal University of São Carlos, São Paulo 13565-905, Brazil
| | - Hans Gesser
- Zoophysiology, Department of Bioscience, Aarhus University, Aarhus 8000, Denmark
| | - Michael S Hedrick
- Department of Biological Sciences, California State University, East Bay, Hayward, CA 94542, USA
| | - Tobias Wang
- Zoophysiology, Department of Bioscience, Aarhus University, Aarhus 8000, Denmark
| |
Collapse
|
3
|
Granger DN, Holm L, Kvietys P. The Gastrointestinal Circulation: Physiology and Pathophysiology. Compr Physiol 2016; 5:1541-83. [PMID: 26140727 DOI: 10.1002/cphy.c150007] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The gastrointestinal (GI) circulation receives a large fraction of cardiac output and this increases following ingestion of a meal. While blood flow regulation is not the intense phenomenon noted in other vascular beds, the combined responses of blood flow, and capillary oxygen exchange help ensure a level of tissue oxygenation that is commensurate with organ metabolism and function. This is evidenced in the vascular responses of the stomach to increased acid production and in intestine during periods of enhanced nutrient absorption. Complimenting the metabolic vasoregulation is a strong myogenic response that contributes to basal vascular tone and to the responses elicited by changes in intravascular pressure. The GI circulation also contributes to a mucosal defense mechanism that protects against excessive damage to the epithelial lining following ingestion of toxins and/or noxious agents. Profound reductions in GI blood flow are evidenced in certain physiological (strenuous exercise) and pathological (hemorrhage) conditions, while some disease states (e.g., chronic portal hypertension) are associated with a hyperdynamic circulation. The sacrificial nature of GI blood flow is essential for ensuring adequate perfusion of vital organs during periods of whole body stress. The restoration of blood flow (reperfusion) to GI organs following ischemia elicits an exaggerated tissue injury response that reflects the potential of this organ system to generate reactive oxygen species and to mount an inflammatory response. Human and animal studies of inflammatory bowel disease have also revealed a contribution of the vasculature to the initiation and perpetuation of the tissue inflammation and associated injury response.
Collapse
Affiliation(s)
- D Neil Granger
- Department of Molecular and Cellular Physiology, LSU Health Science Center-Shreveport, Shreveport, Louisiana, USA
| | - Lena Holm
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Peter Kvietys
- Department of Physiological Sciences, College of Medicine, Alfaisal University, Riyadh, Saudi Arabia
| |
Collapse
|
4
|
Jensen B, Moorman AFM, Wang T. Structure and function of the hearts of lizards and snakes. Biol Rev Camb Philos Soc 2013; 89:302-36. [DOI: 10.1111/brv.12056] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 06/26/2013] [Accepted: 07/30/2013] [Indexed: 12/20/2022]
Affiliation(s)
- Bjarke Jensen
- Department of Bioscience, Zoophysiology; Aarhus University; Aarhus C 8000 Denmark
- Department of Anatomy, Embryology & Physiology, Academic Medical Center; University of Amsterdam; Amsterdam 1105 The Netherlands
| | - Antoon F. M. Moorman
- Department of Anatomy, Embryology & Physiology, Academic Medical Center; University of Amsterdam; Amsterdam 1105 The Netherlands
| | - Tobias Wang
- Department of Bioscience, Zoophysiology; Aarhus University; Aarhus C 8000 Denmark
| |
Collapse
|
5
|
Enok S, Simonsen LS, Pedersen SV, Wang T, Skovgaard N. Humoral regulation of heart rate during digestion in pythons (Python molurus and Python regius). Am J Physiol Regul Integr Comp Physiol 2012; 302:R1176-83. [PMID: 22422667 DOI: 10.1152/ajpregu.00661.2011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pythons exhibit a doubling of heart rate when metabolism increases several times during digestion. Pythons, therefore, represent a promising model organism to study autonomic cardiovascular regulation during the postprandial state, and previous studies show that the postprandial tachycardia is governed by a release of vagal tone as well as a pronounced stimulation from nonadrenergic, noncholinergic (NANC) factors. Here we show that infusion of plasma from digesting donor pythons elicit a marked tachycardia in fasting snakes, demonstrating that the NANC factor resides in the blood. Injections of the gastrin and cholecystokinin receptor antagonist proglumide had no effect on double-blocked heart rate or blood pressure. Histamine has been recognized as a NANC factor in the early postprandial period in pythons, but the mechanism of its release has not been identified. Mast cells represent the largest repository of histamine in vertebrates, and it has been speculated that mast cells release histamine during digestion. Treatment with the mast cell stabilizer cromolyn significantly reduced postprandial heart rate in pythons compared with an untreated group but did not affect double-blocked heart rate. While this study indicates that histamine induces postprandial tachycardia in pythons, its release during digestion is not stimulated by gastrin or cholecystokinin nor is its release from mast cells a stimulant of postprandial tachycardia.
Collapse
Affiliation(s)
- Sanne Enok
- Zoophysiology, Department of Bioscience, Aarhus University, Denmark
| | | | | | | | | |
Collapse
|
6
|
Affiliation(s)
- Juan Zhou
- Department of Anaesthesia, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Vladimir Cerny
- Department of Anaesthesia, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Anesthesiology and Intensive Care Medicine, Charles University Prague, Faculty of Medicine Hradec Kralove, University Hospital Hradec Kralove, Czech Republic
| | - Christian Lehmann
- Department of Anaesthesia, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada
| |
Collapse
|
7
|
|
8
|
Secor SM. Digestive physiology of the Burmese python: broad regulation of integrated performance. ACTA ACUST UNITED AC 2009; 211:3767-74. [PMID: 19043049 DOI: 10.1242/jeb.023754] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
As an apparent adaptation to predictably long episodes of fasting, the sit-and-wait foraging Burmese python experiences unprecedented regulation of gastrointestinal and cardiovascular performance with feeding and fasting. The ingestion of a meal signals the quiescent gut tissues to start secreting digestive acid and enzymes, to upregulate intestinal brush-border enzymes and nutrient transporters, and to grow. An integrated phenomenon, digestion is also characterized by increases in the mass, and presumably the function, of the heart, pancreas, liver and kidneys. Once digestion is complete, the python's stomach and small intestine rapidly downregulate performance. Much of the modulation of intestinal function can be explained by the 5-fold increase in microvillus length and apical surface area with feeding, and the subsequent shortening of the microvilli after digestion has finished. Digestion for the Burmese python is a relatively expensive endeavor, evident by the as much as a 44-fold increase in metabolic rate and equivalent in cost to as much as 37% of the meal's energy. Their large metabolic response is supported by substantial increases in ventilation and cardiac output and the apparent catabolism of glucose and lipids. Unmatched in the magnitude of its numerous physiological responses to feeding, the Burmese python is a very attractive model for examining the capacities and regulatory mechanisms of physiological performance.
Collapse
Affiliation(s)
- Stephen M Secor
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35405, USA.
| |
Collapse
|