Regulation of arteriolar density in adult myocardium during low thyroid conditions.
Low thyroid function induced by either propylthiouracil (PTU) treatment or thyroidectomy surgery led to a reduction of arteriolar density in adult rat myocardium, which can be prevented by treatment with thyroxine or the thyroid hormone analogue 3,5-diiodothyropropionic acid (DITPA). However, many questions related to pathophysiological changes and the regulation of arteriolar density in the heart due to hypothyroidism remain unanswered. Sprague-Dawley rats were treated with PTU in drinking water for 1, 3, and 6weeks, or co-treated with the vasodilator dipyridamole and PTU for 6weeks, or treated with PTU for 6weeks and treatment discontinued for 2 or 4weeks. Heart mass, body mass, cardiac function and myocardial arteriolar density were determined. Arteriolar loss in hypothyroidism induced by PTU treatment progressed gradually with a 22% reduction after 3weeks treatment and 34% by 6weeks which was largely reversed after discontinuing PTU treatment for only 2weeks. Combined treatment with the vasodilator dipyridamole during the 6-week PTU treatment period prevented vessel loss indicating the mechanism of arteriolar loss from hypothyroidism may result from vasoconstriction. These results suggest that thyroid hormone is a powerful regulator of vasculature in adult myocardium, particularly in low thyroid states.
Cardiovascular Research Center, Sanford Research, University of South Dakota, Sioux Falls, South Dakota, USA.
Yingheng
Y
Liu
Benjamin A
BA
Sherer
Rebecca A
RA
Redetzke
A Martin
AM
Gerdes
D000818:Animals; D001160:Arterioles / Q000378:metabolism; D004176:Dipyridamole / Q000494:pharmacology*; D004195:Disease Models, Animal; D005260:Female; D007037:Hypothyroidism / Q000503:physiopathology* / Q000517:prevention & control; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D011441:Propylthiouracil / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013963:Thyroid Hormones / Q000378:metabolism*; D013965:Thyroidectomy; D013997:Time Factors; D014661:Vasoconstriction; D014665:Vasodilator Agents / Q000494:pharmacology
D013963:Thyroid Hormones; D014665:Vasodilator Agents; D004176:Dipyridamole; D011441:Propylthiouracil