Exercise training alters aortic vascular reactivity in hypothyroid rats.
Hypothyroidism induces a number of cardiovascular adaptations in rats, including decreases in blood flow to high-oxidative skeletal muscle and increases in total peripheral resistance. Conversely, exercise training results in elevations in blood flow to high-oxidative skeletal muscle and decreases in vascular resistance. The purpose of this study was to determine whether hypothyroidism induces changes in the vasomotor responses of arterial vessels and whether exercise training modifies these responses. Rats were divided into three groups, sedentary euthyroid (S-Eut), sedentary hypothyroid (S-Hypo), and exercise-trained hypothyroid (ET-Hypo). Responses to vasoactive compounds were examined in vitro using abdominal aortic rings. Maximal isometric contractile tension (g/mm2) evoked by KCl and norepinephrine (NE) were not different among groups. However, sensitivity to KCl [agonist concentration producing 50% of maximal vasoconstrictor response (EC50; in mM): S-Eut, 21.1 +/- 1.1; S-Hypo, 35.7 +/- 2.7; ET-Hypo, 43.8 +/- 2.0] and to NE [EC50 (in M): S-Eut, 4.0 x 10(-8) +/- 2.3 x 10(-8); S-Hypo, 8.3 x 10(-8) +/- 3.4 x 10(-8); ET-Hypo, 3.6 x 10(-7) +/- 1.1 x 10(-7)] was different among groups, and in the order S-Eut > S-Hypo > ET-Hypo. Maximal vasodilator responses induced by acetylcholine (10(-7) M NE preconstriction) were lower in rings from S-Hypo animals than those from S-Eut and ET-Hypo rats. Dilatory responses induced by sodium nitroprusside (SNP) with the same NE preconstriction were not different among groups. However, with a 10(-4) M NE preconstriction, maximal dilatory responses induced by SNP were lower in vessels from hypothyroid animals. Dilatory responses to forskolin (10(-4) M NE preconstriction) were not different among groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Delp
M D
MD
Department of Surgery, Medical College of Pennsylvania, Pittsburgh, USA.
McAllister
R M
RM
Laughlin
M H
MH
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000818:Animals; D001011:Aorta / Q000503:physiopathology*; D002950:Citrate (si)-Synthase / Q000378:metabolism; D007037:Hypothyroidism / Q000503:physiopathology*; D008297:Male; D009132:Muscles / Q000201:enzymology; D009569:Nitric Oxide; D009599:Nitroprusside; D010805:Physical Conditioning, Animal; D011450:Prostaglandin Endoperoxides, Synthetic; D051381:Rats; D017207:Rats, Sprague-Dawley; D013928:Thromboxane A2; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology; D014666:Vasomotor System / Q000187:drug effects
D011450:Prostaglandin Endoperoxides, Synthetic; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009599:Nitroprusside; D009569:Nitric Oxide; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D002950:Citrate (si)-Synthase