PMID- 8594903
OWN - NLM
STAT- MEDLINE
DCOM- 19960408
LR  - 20171213
IS  - 0002-9513 (Print)
IS  - 0002-9513 (Linking)
VI  - 269
IP  - 6 Pt 2
DP  - 1995 Dec
TI  - Muscle blood flow during exercise in sedentary and trained hypothyroid rats.
PG  - H1949-54
AB  - Hypothyroidism is characterized by exercise intolerance. We hypothesized that 
      active muscle blood flow during in vivo exercise is inadequate in the hypothyroid 
      state. Additionally, we hypothesized that endurance exercise training would 
      restore normal blood flow during acute exercise. To test these hypotheses, rats 
      were made hypothyroid (Hypo) over 3-4 mo with propylthiouracil. A subset of Hypo 
      rats was trained (THypo) on a treadmill at 30 m/min (15% grade) for 60 min/day 5 
      days/wk over 10-15 wk. Hypothyroidism was evidenced by approximately 80% 
      reductions in plasma triiodothyronine levels in Hypo and THypo and by 40-50% 
      reductions in citrate synthase activities in high oxidative muscles in Hypo 
      compared with euthyroid (Eut) rats. Training efficacy was indicated by increased 
      (25-100%) citrate synthase activities in muscles of THypo vs. Hypo. Regional 
      blood flows were determined by the radiolabeled microsphere method before 
      exercise and at 1-2 min of treadmill running at 15 m/min (0% grade). Preexercise 
      muscle blood flows were generally similar among groups. During exercise, however, 
      flows were lower in Hypo than in Eut for high oxidative muscles such as the red 
      section of vastus lateralis [277 +/- 24 and 153 +/- 13 (SE) ml.min-1.100 g-1 for 
      Eut and Hypo, respectively; P < 0.01] and vastus intermedius (317 +/- 32 and 187 
      +/- 20 ml.min-1.100 g-1 for Eut and Hypo, respectively; P < 0.01) muscles. 
      Training (THypo) did not normalize these flows (168 +/- 24 and 181 +/- 24 
      ml.min-1.100 g-1 for red section of vastus lateralis and vastus intermedius 
      muscles, respectively). Blood flows to low oxidative muscle, such as the white 
      section of vastus lateralis muscle, were similar among groups (21 +/- 5, 25 +/- 
      4, and 34 +/- 7 ml.min-1.100 g-1 for Eut, Hypo, and THypo, respectively; P = NS). 
      These findings indicate that hypothyroidism is associated with reduced blood flow 
      to skeletal muscle during exercise, suggesting that impaired delivery of 
      nutrients to and/or removal of metabolites from skeletal muscle contributes to 
      the poor exercise tolerance characteristic of hypothyroidism.
FAU - McAllister, R M
AU  - McAllister RM
AD  - Department of Veterinary Biomedical Sciences, College of Veterinary Medicine, 
      University of Missouri, Columbia 65211, USA.
FAU - Delp, M D
AU  - Delp MD
FAU - Thayer, K A
AU  - Thayer KA
FAU - Laughlin, M H
AU  - Laughlin MH
LA  - eng
GR  - HL-36088/HL/NHLBI NIH HHS/United States
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - United States
TA  - Am J Physiol
JT  - The American journal of physiology
JID - 0370511
SB  - IM
MH  - Animals
MH  - Hemodynamics
MH  - Hypothyroidism/*physiopathology
MH  - Male
MH  - Motor Activity/*physiology
MH  - Muscles/*blood supply
MH  - *Physical Exertion
MH  - Rats
MH  - Rats, Sprague-Dawley
MH  - Reference Values
MH  - Regional Blood Flow
EDAT- 1995/12/01 00:00
MHDA- 1995/12/01 00:01
CRDT- 1995/12/01 00:00
PHST- 1995/12/01 00:00 [pubmed]
PHST- 1995/12/01 00:01 [medline]
PHST- 1995/12/01 00:00 [entrez]
AID - 10.1152/ajpheart.1995.269.6.H1949 [doi]
PST - ppublish
SO  - Am J Physiol. 1995 Dec;269(6 Pt 2):H1949-54. doi: 
      10.1152/ajpheart.1995.269.6.H1949.