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

Kadekaro, Massako; Gross, Paul M.; Sokoloff, Louis; Holcomb, Henry H.; Saavedra, Juan M.

doi:10.1016/0006-8993(83)90436-5

Cited by 28 publications

(5 citation statements)

References 17 publications

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“…These results are in agreement with previous observations which, utilizing techniques far less sensitive than the ones used here, failed to detect ANG receptors in posterior pitu itary membrane preparations [8], The low concentration of ANG-binding sites in this tissue raises doubts about a local site of action of ANG in the posterior pituitary in the re lease of vasopressin during dehydration [6], ANG does greatly increase the metabolic activity of the posterior pitu itary after water deprivation, as measured by the deoxyglucose autoradiographic technique [7,12,28]. Glucose metab olism is also increased in the posterior pituitary of DI rats [12,28]. It is reasonable to assume, however, that the main site of action for peripheral ANG in those two models re sides in the circumventricular organs which are not only ac cessible to blood-borne ANG, but also contain the highest ANG-receptor concentrations in the brain [5,10,II].…”

Section: Discussionsupporting

confidence: 76%

Increased Number of Angiotensin II Binding Sites Determined by Autoradiography in Anterior Pituitary of Water-Deprived and Brattleboro Rats

Israel¹,

Plunkett²,

Saavedra³

1986

Neuroendocrinology

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Pituitary angiotensin II (ANG) binding sites were characterized by autoradiography in individual male Long Evans (LE) rats, heterozygous Brattleboro (HZ) rats, and homozygous Brattleboro (DI) rats which were water satiated or water deprived. An additional group of DI rats was treated with arginine vasopressin for 1 week. The technique utilized 8-µm pituitary sections which were incubated with ¹²⁵I-[Sar¹]-ANG in concentrations ranging from 25 pM to 10 nM. Angiotensin binding in the anterior pituitary of water-satiated LE rats was characterized by a single class of high-affinity, saturable sites with a B_max of 1.309 ±119 fmol/mg of protein and a K_a of 0.51 ± 0.03 × 10⁹M^–1l. Compared to LE rats the density of ANG-binding sites in anterior pituitary was higher in DI rats (+84.2%), with HZ having an intermediate concentration (+41.6). Dehydration increased the ANG-binding site density in all groups. Five days of water deprivation increased the number of ANG-binding sites by 86.5% and by 36.9% in LE and HZ rats, respectively, when compared to their water-satiated controls. After 1 day of water deprivation, the ANG-binding site density increased by 19.4% in DI rats. No changes in ANG-binding sites occurred after hormonal replacement with arginine vasopressin in water-satiated DI rats. The binding affinity constant of the agonist for the ANG-binding sites compared with LE rats was decreased in both HZ and DI rats (-27.5 and -19.4%) and was also decreased after 5 days of dehydration in LE rats (-34%) when compared to the water-satiated state. Our results demonstrate alterations in ANG-binding sites in the anterior pituitary gland of both dehydrated Brattleboro rats and LE rats. These findings suggest a role for anterior pituitary ANG receptors in the regulation of fluid metabolism in the rat.

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Section: Discussionsupporting

confidence: 76%

Increased Number of Angiotensin II Binding Sites Determined by Autoradiography in Anterior Pituitary of Water-Deprived and Brattleboro Rats

Israel¹,

Plunkett²,

Saavedra³

1986

Neuroendocrinology

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“…The high metabolic activity in this structure in Brattleboro rats, despite their inability to synthesize vasopressin, has been reported previously [17]. Two recent reports [45,46] have indicated that the pituitary neural lobe does not utilize glucose but rather selectively metabolizes fatty acids as a source for energy metabolism.…”

Section: Discussionmentioning

confidence: 84%

“…The major findings of this study are: (1) in comparison with the control Long-Evans rats, homozygous Brattleboro rats have high rates of glucose utilization, not only in the subfornical organ and pituitary neural lobe [17], but also in the septal triangular nucleus and in the habenular complex; (2) Brattleboro rats are more sensitive to the effects of water deprivation than control Long-Evans rats, as indicated by the higher metabolic response in the subfornical organ and in the septal triangular nucleus; and (3) several structures anatomically connected to the subfornical organ, and other brain regions, are activated by short-term dehydration in both groups of rats.…”

Section: Discussionmentioning

confidence: 90%

“…Brattleboro rats homo zygous for diabetes insipidus exhibit all the signs and symp toms of chronic dehydration and present high rates of glu cose utilization in the subfornical organ and pituitary neu ral lobe [17]. Angiotensin II, an important stimulus for thirst responses [30,37], is significantly elevated in the Received: January 18, 1985 Accepted after revision: April 10, 1985 plasma of Brattleboro rats [29].…”

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confidence: 99%

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Local Cerebral Glucose Utilization in Long-Evans and Brattleboro Rats during Acute Dehydration

1986

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The quantitative autoradiographic deoxyglucose method was used to study the effects of acute dehydration on local cerebral glucose utilization in Long-Evans and homozygous Brattleboro rats. Water-sated Brattleboro rats had high rates of glucose utilization in the subfornical organ, habenular complex, septal triangular nucleus and pituitary neural lobe. Deprivation of water for 16–18 h enhanced glucose utilization in these structures, more intensely in the Brattleboro rats, and activated others, particularly those connected to the subfornical organ. In Long-Evans rats, water deprivation increased metabolic activity in the subfornical organ, in several structures with which it is connected, and in other brain regions putatively involved in maintaining fluid balance.

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“…changes are seen in the neural lobes of homozygous Brattleboro rats, which do not synthesize vaso pressin and are thus chronically dehydrated (Sokol and Yaltin, 1965;Friesen and Astwood, 1967;Scott, 1968;Kadekaro et a!. , 1983;Sutherland et a!.…”

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confidence: 99%

Rapid Amino Acid Uptake in Rat Pituitary Neural Lobe during Functional Stimulation by Chronic Dehydration

Gross

Blasberg

Fenstermacher

et al. 1985

J Cereb Blood Flow Metab

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We studied the transfer of a small neutral amino acid, alpha-aminoisobutyric acid, from arterial blood into the pituitary neural lobe in normal rats and in rats deprived of water for 5 days. A threefold increase in the neural lobe uptake of the amino acid was found in the chronically dehydrated rats. Possible causes for this effect include enlargement of the capillary and pituicyte membrane surface areas available for solute flux and increased permeability of these membranes. Such functional and structural alterations may be associated with an increase in protein turnover in the neural lobe during dehydration.

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

Cited by 28 publications

References 17 publications

Increased Number of Angiotensin II Binding Sites Determined by Autoradiography in Anterior Pituitary of Water-Deprived and Brattleboro Rats

Increased Number of Angiotensin II Binding Sites Determined by Autoradiography in Anterior Pituitary of Water-Deprived and Brattleboro Rats

Local Cerebral Glucose Utilization in Long-Evans and Brattleboro Rats during Acute Dehydration

Rapid Amino Acid Uptake in Rat Pituitary Neural Lobe during Functional Stimulation by Chronic Dehydration

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