Reduced plasma volume and mesenteric vascular reactivity in obese Zucker rats

Ana M. Schreihofer, Clark D. Hair, David W. Stepp

Research output: Contribution to journalArticle

54 Citations (Scopus)

Abstract

Obese Zucker rats (OZR) are mildly hypertensive with an apparently elevated sympathetic vasomotor tone compared with lean Zucker rats (LZR). Studies have also suggested enhanced adrenergic pressor reactivity in OZR but assumed comparable baroreflexes, or blood volume-to-body weight ratio, to LZR. In 15-wk-old OZR and LZR, we measured plasma volume and vascular reactivity to norepinephrine (NE) and phenylephrine (PE) with doses evaluated by body weight and plasma volume. Plasma volume measured by dye dilution (Evans blue; 200 μl of 0.5%) showed that OZR had comparable blood volumes to LZR but lower blood volume-to-body weight ratio (3.4 ± 0.2 ml/100 g) than LZR (5.7 ± 0.2 ml/100 g, P < 0.05). Ganglionic blockade (mecamylamine, 4 mg/kg) in isoflurane-anesthetized rats produced larger decreases in arterial pressure in OZR compared with LZR (52 ± 2 vs. 46 ± 2 mmHg). Pressor responses to NE (0.01-10 μg/kg) were exaggerated with doses analyzed by body weight but not analyzed by drug quantity. Pressor responses to PE (1-24 μg/kg) showed no difference with doses analyzed by body weight, but, analyzed by drug quantity, OZR showed a slight decrease in pressor reactivity. PE-induced increases in vascular resistance were exaggerated in the hindlimb circulation of OZR, normal in the renal circulation, and attenuated in the mesenteric circulation. The timing of the peak pressor response to PE corresponded with the increase in mesenteric vascular resistance, followed by rises in hindlimb and renal resistance. These data suggest that systemic adrenergic pressor reactivity is not enhanced in OZR, despite exaggerated vascular reactivity in the hindlimb of the OZR.

Original languageEnglish (US)
Pages (from-to)R253-R261
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume288
Issue number1 57-1
DOIs
StatePublished - Jan 1 2005

Fingerprint

Zucker Rats
Plasma Volume
Blood Vessels
Phenylephrine
Body Weight
Hindlimb
Blood Volume
Vascular Resistance
Adrenergic Agents
Norepinephrine
Splanchnic Circulation
Mecamylamine
Evans Blue
Baroreflex
Renal Circulation
Isoflurane

Keywords

  • Blood flow
  • Skeletal muscle

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

Cite this

Reduced plasma volume and mesenteric vascular reactivity in obese Zucker rats. / Schreihofer, Ana M.; Hair, Clark D.; Stepp, David W.

In: American Journal of Physiology - Regulatory Integrative and Comparative Physiology, Vol. 288, No. 1 57-1, 01.01.2005, p. R253-R261.

Research output: Contribution to journalArticle

@article{59b817fbb3e645799239df510b6b302b,
title = "Reduced plasma volume and mesenteric vascular reactivity in obese Zucker rats",
abstract = "Obese Zucker rats (OZR) are mildly hypertensive with an apparently elevated sympathetic vasomotor tone compared with lean Zucker rats (LZR). Studies have also suggested enhanced adrenergic pressor reactivity in OZR but assumed comparable baroreflexes, or blood volume-to-body weight ratio, to LZR. In 15-wk-old OZR and LZR, we measured plasma volume and vascular reactivity to norepinephrine (NE) and phenylephrine (PE) with doses evaluated by body weight and plasma volume. Plasma volume measured by dye dilution (Evans blue; 200 μl of 0.5{\%}) showed that OZR had comparable blood volumes to LZR but lower blood volume-to-body weight ratio (3.4 ± 0.2 ml/100 g) than LZR (5.7 ± 0.2 ml/100 g, P < 0.05). Ganglionic blockade (mecamylamine, 4 mg/kg) in isoflurane-anesthetized rats produced larger decreases in arterial pressure in OZR compared with LZR (52 ± 2 vs. 46 ± 2 mmHg). Pressor responses to NE (0.01-10 μg/kg) were exaggerated with doses analyzed by body weight but not analyzed by drug quantity. Pressor responses to PE (1-24 μg/kg) showed no difference with doses analyzed by body weight, but, analyzed by drug quantity, OZR showed a slight decrease in pressor reactivity. PE-induced increases in vascular resistance were exaggerated in the hindlimb circulation of OZR, normal in the renal circulation, and attenuated in the mesenteric circulation. The timing of the peak pressor response to PE corresponded with the increase in mesenteric vascular resistance, followed by rises in hindlimb and renal resistance. These data suggest that systemic adrenergic pressor reactivity is not enhanced in OZR, despite exaggerated vascular reactivity in the hindlimb of the OZR.",
keywords = "Blood flow, Skeletal muscle",
author = "Schreihofer, {Ana M.} and Hair, {Clark D.} and Stepp, {David W.}",
year = "2005",
month = "1",
day = "1",
doi = "10.1152/ajpregu.00498.2004",
language = "English (US)",
volume = "288",
pages = "R253--R261",
journal = "American Journal of Physiology - Heart and Circulatory Physiology",
issn = "0363-6135",
publisher = "American Physiological Society",
number = "1 57-1",

}

TY - JOUR

T1 - Reduced plasma volume and mesenteric vascular reactivity in obese Zucker rats

AU - Schreihofer, Ana M.

AU - Hair, Clark D.

AU - Stepp, David W.

PY - 2005/1/1

Y1 - 2005/1/1

N2 - Obese Zucker rats (OZR) are mildly hypertensive with an apparently elevated sympathetic vasomotor tone compared with lean Zucker rats (LZR). Studies have also suggested enhanced adrenergic pressor reactivity in OZR but assumed comparable baroreflexes, or blood volume-to-body weight ratio, to LZR. In 15-wk-old OZR and LZR, we measured plasma volume and vascular reactivity to norepinephrine (NE) and phenylephrine (PE) with doses evaluated by body weight and plasma volume. Plasma volume measured by dye dilution (Evans blue; 200 μl of 0.5%) showed that OZR had comparable blood volumes to LZR but lower blood volume-to-body weight ratio (3.4 ± 0.2 ml/100 g) than LZR (5.7 ± 0.2 ml/100 g, P < 0.05). Ganglionic blockade (mecamylamine, 4 mg/kg) in isoflurane-anesthetized rats produced larger decreases in arterial pressure in OZR compared with LZR (52 ± 2 vs. 46 ± 2 mmHg). Pressor responses to NE (0.01-10 μg/kg) were exaggerated with doses analyzed by body weight but not analyzed by drug quantity. Pressor responses to PE (1-24 μg/kg) showed no difference with doses analyzed by body weight, but, analyzed by drug quantity, OZR showed a slight decrease in pressor reactivity. PE-induced increases in vascular resistance were exaggerated in the hindlimb circulation of OZR, normal in the renal circulation, and attenuated in the mesenteric circulation. The timing of the peak pressor response to PE corresponded with the increase in mesenteric vascular resistance, followed by rises in hindlimb and renal resistance. These data suggest that systemic adrenergic pressor reactivity is not enhanced in OZR, despite exaggerated vascular reactivity in the hindlimb of the OZR.

AB - Obese Zucker rats (OZR) are mildly hypertensive with an apparently elevated sympathetic vasomotor tone compared with lean Zucker rats (LZR). Studies have also suggested enhanced adrenergic pressor reactivity in OZR but assumed comparable baroreflexes, or blood volume-to-body weight ratio, to LZR. In 15-wk-old OZR and LZR, we measured plasma volume and vascular reactivity to norepinephrine (NE) and phenylephrine (PE) with doses evaluated by body weight and plasma volume. Plasma volume measured by dye dilution (Evans blue; 200 μl of 0.5%) showed that OZR had comparable blood volumes to LZR but lower blood volume-to-body weight ratio (3.4 ± 0.2 ml/100 g) than LZR (5.7 ± 0.2 ml/100 g, P < 0.05). Ganglionic blockade (mecamylamine, 4 mg/kg) in isoflurane-anesthetized rats produced larger decreases in arterial pressure in OZR compared with LZR (52 ± 2 vs. 46 ± 2 mmHg). Pressor responses to NE (0.01-10 μg/kg) were exaggerated with doses analyzed by body weight but not analyzed by drug quantity. Pressor responses to PE (1-24 μg/kg) showed no difference with doses analyzed by body weight, but, analyzed by drug quantity, OZR showed a slight decrease in pressor reactivity. PE-induced increases in vascular resistance were exaggerated in the hindlimb circulation of OZR, normal in the renal circulation, and attenuated in the mesenteric circulation. The timing of the peak pressor response to PE corresponded with the increase in mesenteric vascular resistance, followed by rises in hindlimb and renal resistance. These data suggest that systemic adrenergic pressor reactivity is not enhanced in OZR, despite exaggerated vascular reactivity in the hindlimb of the OZR.

KW - Blood flow

KW - Skeletal muscle

UR - http://www.scopus.com/inward/record.url?scp=11144257696&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=11144257696&partnerID=8YFLogxK

U2 - 10.1152/ajpregu.00498.2004

DO - 10.1152/ajpregu.00498.2004

M3 - Article

C2 - 15345476

AN - SCOPUS:11144257696

VL - 288

SP - R253-R261

JO - American Journal of Physiology - Heart and Circulatory Physiology

JF - American Journal of Physiology - Heart and Circulatory Physiology

SN - 0363-6135

IS - 1 57-1

ER -