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Adaptations to iron deficiency: cardiac functional responsiveness to norepinephrine, arterial remodeling, and the effect of beta-blockade on cardiac hypertrophy.

Turner LR, Premo DA, Gibbs BJ, Hearthway ML, Motsko M, Sappington A, Walker L, Mullendore ME, Chew HG - BMC Physiol. (2002)

Bottom Line: Propanolol was associated with an increase in heart to body mass ratio.ID cardiac hypertrophy results in an increased inotropic, but not chronotropic response to the sympathetic neurotransmitter, norepinephrine.Increased aortic diameter is consistent with a flow-dependent vascular remodeling; increased distensibility may reflect decreased vascular collagen content.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological Sciences R,A, Henson School of Science and Technology Salisbury State University Salisbury, MD 21801, USA. lexssu@hotmail.com

ABSTRACT

Background: Iron deficiency (ID) results in ventricular hypertrophy, believed to involve sympathetic stimulation. We hypothesized that with ID 1) intravenous norepinephrine would alter heart rate (HR) and contractility, 2) abdominal aorta would be larger and more distensible, and 3) the beta-blocker propanolol would reduce hypertrophy.

Methods: 1) 30 CD rats were fed an ID or replete diet for 1 week or 1 month. Norepinephrine was infused via jugular vein; pressure was monitored at carotid artery. Saline infusions were used as a control. The pressure trace was analyzed for HR, contractility, systolic and diastolic pressures. 2) Abdominal aorta catheters inflated the aorta, while digital microscopic images were recorded at stepwise pressures to measure arterial diameter and distensibility. 3) An additional 10 rats (5 ID, 5 control) were given a daily injection of propanolol or saline. After 1 month, the hearts were excised and weighed.

Results: Enhanced contractility, but not HR, was associated with ID hypertrophic hearts. Systolic and diastolic blood pressures were consistent with an increase in arterial diameter associated with ID. Aortic diameter at 100 mmHg and distensibility were increased with ID. Propanolol was associated with an increase in heart to body mass ratio.

Conclusions: ID cardiac hypertrophy results in an increased inotropic, but not chronotropic response to the sympathetic neurotransmitter, norepinephrine. Increased aortic diameter is consistent with a flow-dependent vascular remodeling; increased distensibility may reflect decreased vascular collagen content. The failure of propanolol to prevent hypertrophy suggests that ID hypertrophy is not mediated via beta-adrenergic neurotransmission.

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Rat Growth Rate and Final Body Mass
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Figure 1: Rat Growth Rate and Final Body Mass

Mentions: Rat growth rate is shown in figure 1. There were no differences between any of the experimental groups (see Materials and Methods) until the animals reached 45 days of age, after which, iron deficient rats are of less mass than controls (*, p < 0.05). Figure 1 also shows the final mean body mass of the four experimental groups. Iron deficient and control groups more than doubled their body mass from 1 week to 1 month on the respective diets (†, p < 0.0001). The control rats also had a significantly greater mass than the iron deficient rats (p = 0.0004) in the one month group (*, p = 0.0006), but not at one week (p = 0.1530). The control rats in this study increased mass at a rate similar to that published for the ad libitum fed CD rat [41,42], suggesting growth was inhibited by iron deficiency. It is likely that growth inhibition is attributable to metabolic causes arising from both oxygen delivery and mitochondrial insufficiencies associated with iron deficiency [14]. The growth data for both the control and iron deficient groups are also similar to that reported for male Wistar rats fed an iron and copper deficient diet [15], but the iron deficient rats at 52 days of age were larger than reports of 10 week old Harlan Sprague-Dawley rats fed an AIN-76 iron deficient diet [17].


Adaptations to iron deficiency: cardiac functional responsiveness to norepinephrine, arterial remodeling, and the effect of beta-blockade on cardiac hypertrophy.

Turner LR, Premo DA, Gibbs BJ, Hearthway ML, Motsko M, Sappington A, Walker L, Mullendore ME, Chew HG - BMC Physiol. (2002)

Rat Growth Rate and Final Body Mass
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC65049&req=5

Figure 1: Rat Growth Rate and Final Body Mass
Mentions: Rat growth rate is shown in figure 1. There were no differences between any of the experimental groups (see Materials and Methods) until the animals reached 45 days of age, after which, iron deficient rats are of less mass than controls (*, p < 0.05). Figure 1 also shows the final mean body mass of the four experimental groups. Iron deficient and control groups more than doubled their body mass from 1 week to 1 month on the respective diets (†, p < 0.0001). The control rats also had a significantly greater mass than the iron deficient rats (p = 0.0004) in the one month group (*, p = 0.0006), but not at one week (p = 0.1530). The control rats in this study increased mass at a rate similar to that published for the ad libitum fed CD rat [41,42], suggesting growth was inhibited by iron deficiency. It is likely that growth inhibition is attributable to metabolic causes arising from both oxygen delivery and mitochondrial insufficiencies associated with iron deficiency [14]. The growth data for both the control and iron deficient groups are also similar to that reported for male Wistar rats fed an iron and copper deficient diet [15], but the iron deficient rats at 52 days of age were larger than reports of 10 week old Harlan Sprague-Dawley rats fed an AIN-76 iron deficient diet [17].

Bottom Line: Propanolol was associated with an increase in heart to body mass ratio.ID cardiac hypertrophy results in an increased inotropic, but not chronotropic response to the sympathetic neurotransmitter, norepinephrine.Increased aortic diameter is consistent with a flow-dependent vascular remodeling; increased distensibility may reflect decreased vascular collagen content.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological Sciences R,A, Henson School of Science and Technology Salisbury State University Salisbury, MD 21801, USA. lexssu@hotmail.com

ABSTRACT

Background: Iron deficiency (ID) results in ventricular hypertrophy, believed to involve sympathetic stimulation. We hypothesized that with ID 1) intravenous norepinephrine would alter heart rate (HR) and contractility, 2) abdominal aorta would be larger and more distensible, and 3) the beta-blocker propanolol would reduce hypertrophy.

Methods: 1) 30 CD rats were fed an ID or replete diet for 1 week or 1 month. Norepinephrine was infused via jugular vein; pressure was monitored at carotid artery. Saline infusions were used as a control. The pressure trace was analyzed for HR, contractility, systolic and diastolic pressures. 2) Abdominal aorta catheters inflated the aorta, while digital microscopic images were recorded at stepwise pressures to measure arterial diameter and distensibility. 3) An additional 10 rats (5 ID, 5 control) were given a daily injection of propanolol or saline. After 1 month, the hearts were excised and weighed.

Results: Enhanced contractility, but not HR, was associated with ID hypertrophic hearts. Systolic and diastolic blood pressures were consistent with an increase in arterial diameter associated with ID. Aortic diameter at 100 mmHg and distensibility were increased with ID. Propanolol was associated with an increase in heart to body mass ratio.

Conclusions: ID cardiac hypertrophy results in an increased inotropic, but not chronotropic response to the sympathetic neurotransmitter, norepinephrine. Increased aortic diameter is consistent with a flow-dependent vascular remodeling; increased distensibility may reflect decreased vascular collagen content. The failure of propanolol to prevent hypertrophy suggests that ID hypertrophy is not mediated via beta-adrenergic neurotransmission.

Show MeSH
Related in: MedlinePlus