Cerebral metabolic and hormonal activations during hemorrhage in sinoaortic-denervated rats

1990 ◽  
Vol 259 (2) ◽  
pp. R305-R312 ◽  
Author(s):  
M. Kadekaro ◽  
J. Y. Summy-Long ◽  
M. L. Terrell ◽  
H. Lekan ◽  
H. E. Gary ◽  
...  
Keyword(s):  
High Pressure ◽  
Angiotensin Ii ◽  
Glucose Metabolism ◽  
Blood Volume ◽  
Glucose Utilization ◽  
Area Postrema ◽  
Subfornical Organ ◽  
Neural Lobe ◽  
Metabolic Activities ◽  
Supraoptic Nuclei

Denervation of sinoaortic baroreceptors in normovolemic rats selectively increases glucose utilization in the median eminence and pituitary neural lobe and enhances secretion of vasopressin and oxytocin. Hemorrhage in denervated animals increases further glucose metabolism in these structures and stimulates the release of both neurohypophysial hormones with preferentially a greater effect on vasopressin. Similar increases in glucose metabolism in these structures with a greater release of vasopressin are observed in sham-operated animals during hemorrhage. Absence of high-pressure receptors, therefore, does not modify the preferential release of vasopressin during hypovolemia. Hemorrhage also increases glucose utilization in the paraventricular and supraoptic nuclei, area postrema, and subfornical organ in sham-operated and denervated rats but only after a 20% blood reduction. The results indicate that decreased inputs from low-pressure receptors during hemorrhage increase the activity of the hypothalamoneurohypophysial system after small reductions in blood volume and that the activity of this system is tonically inhibited by baroreceptors. The activities of structures responsive to circulating angiotensin II (subfornical organ and area postrema) are stimulated by larger reductions in blood volume and their metabolic activities are not tonically influenced by high-pressure receptors.

Effects of sinoaortic denervation on glucose utilization in the subfornical organ and pituitary neural lobe during administration of angiotensin II

Peptides ◽  
1989 ◽  
Vol 10 (1) ◽  
pp. 103-108 ◽  
Author(s):  
Massako Kadekaro ◽  
Mischelle Creel ◽  
Mary Lee Terrell ◽  
Helena A. Lekan ◽  
Howard E. Gary ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Glucose Utilization ◽  
Subfornical Organ ◽  
Neural Lobe

Atriopeptin prevents angiotensin II-stimulated glucose utilization in the subfornical organ

Peptides ◽  
1990 ◽  
Vol 11 (4) ◽  
pp. 837-842 ◽  
Author(s):  
Eva Nermo-Lindquist ◽  
Massako Kadekaro ◽  
Mary Lee Terrell ◽  
James Nassar ◽  
Helena Lekan ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Glucose Utilization ◽  
Subfornical Organ

Enalapril decreases angiotensin II receptors in subfornical organ of SHR

1989 ◽  
Vol 256 (6) ◽  
pp. H1609-H1614 ◽  
Author(s):  
A. J. Nazarali ◽  
J. S. Gutkind ◽  
F. M. Correa ◽  
J. M. Saavedra
Keyword(s):  
Angiotensin Ii ◽  
Angiotensin Converting Enzyme ◽  
Enzyme Inhibitor ◽  
Area Postrema ◽  
Subfornical Organ ◽  
Ang Ii ◽  
Converting Enzyme ◽  
Converting Enzyme Inhibitors ◽  
Wky Rats ◽  
Enalapril Treatment

We studied brain angiotensin II (ANG II) receptors by quantitative autoradiography in adult normotensive Wistar-Kyoto (WKY) rats and in spontaneously hypertensive rats (SHR) after treating the rats with the converting-enzyme inhibitor enalapril, 25 mg/kg, po daily for 14 days. Enalapril treatment decreased blood pressure in only SHR, inhibited plasma angiotensin-converting enzyme activity by 85%, and increased plasma ANG I concentration and renin activity in both WKY and SHR. In the untreated SHR animals, ANG II receptor concentrations were higher in the subfornical organ, the area postrema, the nucleus of the solitary tract, and the inferior olive when compared with the untreated WKY rats. Enalapril treatment produced a large decrease in only subfornical organ ANG II receptors of SHR. The selective reversal of the alteration in subfornical organ ANG II receptors in SHR may indicate a decreased central response to ANG II and may be related to the mode of action of angiotensin-converting enzyme inhibitors in this model.

Morphology and physiology of capillary systems in subregions of the subfornical organ and area postrema

1991 ◽  
Vol 69 (7) ◽  
pp. 1010-1025 ◽  
Author(s):  
Paul M. Gross
Keyword(s):  
Blood Flow ◽  
Blood Volume ◽  
Transit Time ◽  
Area Postrema ◽  
Subfornical Organ ◽  
Type I ◽  
Electron Microscopic ◽  
Brain Surface ◽  
Body Organ ◽  
Tissue Region

From recent morphological and physiological studies of capillaries, I shall review four new or revised concepts about blood–tissue communication in the subfornical organ (SFO) and area postrema (AP). First, the capillary systems of SFO and AP exhibit subregional differentiation correlated topographically with cytoarchitecture, densities of immunoreactivity for several peptides and amines, cellular sensitivity to neuroactive substances, afferent neural terminations, and tissue metabolic activity. Thus, contrary to frequent citations, the angioarchitecture and microcirculatory physiology of these small sensory nuclei are not homogeneous. Second, electron microscopic, morphometric, and topographical studies reveal that SFO contains three different types of capillary and AP has two. The differentiated capillary morphology appears to be well organized for specialized functions particularly in SFO subregions. No other body organ or small tissue region is known to have such capillary diversity, further highlighting the complex functions served by SFO. Third, pools of interstitial fluid (Virchow–Robin spaces) surrounding type I and III capillaries in SFO and AP may participate in the receptive properties of these organs as low-resistance pathways for rapid dispersion of blood-borne hormones inside their organ boundaries. The parenchymal walls of Virchow–Robin spaces appear to harbour metabolic mechanisms for hormones such as angiotensin II, and thus could vastly extend the effective blood–brain surface area of permeable capillaries in SFO and AP. Fourth, SFO and AP bear similar physiological characteristics of high blood volume, yet relatively low rates of blood flow. Accordingly, intracapillary blood velocity must be quite slow in these organs, and the duration of transit by blood and circulating messengers rather protracted. This feature of slow blood transit time likely compounds the sensory capability of SFO and AP, rendering increased contact time for blood-borne hormones to penetrate the permeable capillaries of these structures and interact with their known dense populations of receptors for several homeostatic substances involved in regulation of blood pressure and body fluids.Key words: morphometry, topography, cytoarchitecture, fenestrations, vesicles, blood flow, permeability, blood volume, transit time, pericapillary spaces.

Osmoregulatory fluid intake but not hypovolemic thirst is intact in mice lacking angiotensin

2008 ◽  
Vol 294 (5) ◽  
pp. R1533-R1543 ◽  
Author(s):  
Michael J. McKinley ◽  
Lesley L. Walker ◽  
Theodora Alexiou ◽  
Andrew M. Allen ◽  
Duncan J. Campbell ◽  
...  
Keyword(s):  
Polyethylene Glycol ◽  
Angiotensin Ii ◽  
Water Intake ◽  
Subfornical Organ ◽  
Salt Appetite ◽  
Neural Pathways ◽  
Daily Water Intake ◽  
Similar Dose ◽  
Central Origin ◽  
Supraoptic Nuclei

Water intakes in response to hypertonic, hypovolemic, and dehydrational stimuli were investigated in mice lacking angiotensin II as a result of deletion of the angiotensinogen gene (Agt−/− mice), and in C57BL6 wild-type (WT) mice. Baseline daily water intake in Agt−/− mice was approximately threefold that of WT mice because of a renal developmental disorder of the urinary concentrating mechanisms in Agt−/− mice. Intraperitoneal injection of hypertonic saline (0.4 and 0.8 mol/l NaCl) caused a similar dose-dependent increase in water intake in both Agt−/− and WT mice during the hour following injection. As well, Agt−/− mice drank appropriate volumes of water following water deprivation for 7 h. However, Agt−/− mice did not increase water or 0.3 mol/l NaCl intake in the 8 h following administration of a hypovolemic stimulus (30% polyethylene glycol sc), whereas WT mice increased intakes of both solutions during this time. Osmoregulatory regions of the brain [hypothalamic paraventricular and supraoptic nuclei, median preoptic nucleus, organum vasculosum of the lamina terminalis (OVLT), and subfornical organ] showed an increased number of neurons exhibiting Fos-immunoreactivity in response to intraperitoneal hypertonic NaCl in both Agt−/− mice and WT mice. Polyethylene glycol treatment increased Fos-immunoreactivity in the subfornical organ, OVLT, and supraoptic nuclei in WT mice but only increased Fos-immunoreactivity in the supraoptic nucleus in Agt−/− mice. These data show that brain angiotensin is not essential for the adequate functioning of neural pathways mediating osmoregulatory thirst. However, angiotensin II of either peripheral or central origin is probably necessary for thirst and salt appetite that results from hypovolemia.

Elevated glucose utilization in subfornical organ and pituitary neural lobe of the Brattleboro rat

1983 ◽  
Vol 275 (1) ◽  
pp. 189-193 ◽  
Author(s):  
Massako Kadekaro ◽  
Paul M. Gross ◽  
Louis Sokoloff ◽  
Henry H. Holcomb ◽  
Juan M. Saavedra
Keyword(s):  
Glucose Utilization ◽  
Subfornical Organ ◽  
Brattleboro Rat ◽  
Neural Lobe ◽  
Elevated Glucose

Selective metabolic stimulation of the subfornical organ and pituitary neural lobe by peripheral angiotensin II

Peptides ◽  
1985 ◽  
Vol 6 ◽  
pp. 145-152 ◽  
Author(s):  
Paul M. Gross ◽  
Massako Kadekaro ◽  
David W. Andrews ◽  
Louis Sokoloff ◽  
Juan M. Saavedra
Keyword(s):  
Angiotensin Ii ◽  
Subfornical Organ ◽  
Neural Lobe ◽  
Metabolic Stimulation ◽  
Stimulation Of

GLUT2 and hexokinase control proximodistal gradient of intestinal glucose metabolism in the newborn pig

1997 ◽  
Vol 272 (6) ◽  
pp. G1530-G1539 ◽  
Author(s):  
C. Cherbuy ◽  
B. Darcy-Vrillon ◽  
L. Posho ◽  
P. Vaugelade ◽  
M. T. Morel ◽  
...  
Keyword(s):  
Glucose Metabolism ◽  
Glucose Transporter ◽  
Glucose Utilization ◽  
Specific Effect ◽  
Glucose Consumption ◽  
Utilization Rate ◽  
Glucose Turnover ◽  
Proximal Jejunum ◽  
A Site

We have reported previously that a high glycolytic capacity develops soon after birth in enterocytes isolated from suckling newborn pigs. In the present work, we investigated whether such metabolic changes could affect intestinal glucose utilization in vivo and examined possible variations in glucose metabolism along the small intestine. Glucose utilization by individual tissues was assessed using the 2-deoxyglucose technique. The overall glucose utilization rate was doubled in suckling vs. fasting 2-day-old pigs because of significantly higher rates in all tissues studied, except for the brain. In parallel, enterocytes were isolated from the proximal, medium, or distal jejunoileum of newborn vs. 2-day-old pigs and assessed for their capacity to utilize, transport, and phosphorylate glucose. Intestinal glucose consumption accounted for approximately 15% of glucose turnover rate in suckling vs. 8% in fasting pigs. Moreover, there was a proximal-to-distal gradient of glucose utilization in the intestinal mucosa of suckling pigs. Such a gradient was also evidenced on isolated enterocytes. The stimulation of both hexokinase activity (HK2 isoform) and basolateral glucose transporter (GLUT2), as observed in the proximal jejunum, could account for such a site-specific effect of suckling.

Cerebral metabolic responses and vasopressin and oxytocin secretions during progressive water deprivation in rats

1992 ◽  
Vol 262 (2) ◽  
pp. R310-R317 ◽  
Author(s):  
M. Kadekaro ◽  
J. Y. Summy-Long ◽  
S. Freeman ◽  
J. S. Harris ◽  
M. L. Terrell ◽  
...  
Keyword(s):  
Water Deprivation ◽  
Glucose Utilization ◽  
Extracellular Volume ◽  
Plasma Osmolality ◽  
Ventrolateral Medulla ◽  
Ang Ii ◽  
Neural Lobe ◽  
Arterial Blood ◽  
Organum Vasculosum Laminae Terminalis ◽  
Enhanced Secretion

Progressive water deprivation increased plasma osmolality, plasma Na+ concentration, and hematocrit in proportion to the severity of dehydration. With increases of 2% in plasma osmolality (24 h dehydration), glucose utilization increased in the supraoptic nuclei and tended to increase in the neural lobe. With further dehydration, glucose utilization also increased in the paraventricular nuclei. These increases were paralleled by depletion of vasopressin and oxytocin contents in the neural lobe and by the enhanced secretion of both hormones into plasma, with a predominant increase of vasopressin. These changes were proportional to the degree of dehydration. With progression of dehydration, decreases in intracellular and extracellular volumes accentuate. Reductions in extracellular volume result in increased angiotensin II (ANG II) formation. Accordingly, glucose utilization in the subfornical organ (SFO), a primary site of ANG II action, increased after 48 and 72 h of dehydration. The median preoptic nucleus, which receives direct inputs from the SFO, also increased glucose utilization at these times. Glucose utilization also increased in the organum vasculosum laminae terminalis, probably in response to the converging inputs from osmoreceptors, volume receptors, and ANG II receptors. Decreases in glucose utilization were observed in the caudal and rostral ventrolateral medulla, perhaps as compensatory responses to decreased extracellular volume to prevent fall in arterial blood pressure.

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