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Effects of tetraiodothyronine and triiodothyronine on hamster cheek pouch microcirculation (Articolo in rivista)

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Effects of tetraiodothyronine and triiodothyronine on hamster cheek pouch microcirculation (Articolo in rivista) (literal)

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Colantuoni, A; Marchiafava, P; Lapi, D; Forini, F.S; Iervasi, G. (2005)
Effects of tetraiodothyronine and triiodothyronine on hamster cheek pouch microcirculation
in American journal of physiology. Heart and circulatory physiology
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Dept. of Neuroscience Federico II, University of Medical School, Naples, Italy Dept. of Physiology and Biochemistry, University of Pisa, Pisa, Italy Consiglio Nazionale della Ricerche, Institute of Clinical Physiology, Pisa, Italy Dept. of Neuroscience Federico II, Univ. Medical School, Via S. Pansini, 5 80131 Naples, Italy (literal)

Titolo

Effects of tetraiodothyronine and triiodothyronine on hamster cheek pouch microcirculation (literal)

Abstract

The aim of the present study was to assess the effects of topically applied triiodothyronine (T3) and thyroxine (T4) on the arterioles of hamster cheek pouch microcirculation in vivo. Microvessels were visualized using a fluorescent microscopy technique. Topical application of T3 (3.08, 30.8, 61.5, 307, 615, and 6,150 nM/l) consistently induced dose-dependent dilation of arterioles within 2.0 ± 0.5 min of administration. The application of T4 (150, 257, 514, and 5,140 nM/l) caused different dose-dependent effects: dilation at the three lower doses within 16 ± 2 min and rhythmic diameter changes at the highest dose. Aging of hamsters did not alter the arteriolar responses to T3 and T4. T3-induced dilation was countered by the inhibition of nitric oxide synthase with NG-nitro-L-arginine-methyl ester or NG-nitro-L-arginine. Iopanoic acid (IPA), which inhibits types I and II 5?-deiodinase, abolished the dilation elicited by 514 nM T4 but did not affect T3-dependent dilation. 6-Propyl-2-thiouracil (PTU), which inhibits type I 5?-deiodinase only, did not affect the dilation induced by T4. IPA and PTU did not impair arteriolar dilation induced by acetylcholine or sodium nitroprusside. These results indicate that T3 induces arteriolar dilation, likely through nitric oxide release. The local conversion of T4 to T3 appears to be crucial for the dilation induced by T4. Copyright © 2005 the American Physiological Society. (literal)

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