Johanson V, Ofverholm T, Ericson L E
Department of Anatomy, University of Göteborg, Sweden.
Mol Cell Endocrinol. 1988 Sep;59(1-2):27-34. doi: 10.1016/0303-7207(88)90192-x.
Using a newly developed infusion technique, the in vivo effects of forskolin and dibuturyl cyclic AMP (dbcAMP) on exocytosis and endocytosis in thyroid follicle cells were studied in thyroxine-treated rats and mice. Reactants were selectively infused via the superior thyroid artery to one thyroid lobe. The contralateral lobe served as a control. In the rat, a supramaximal i.v. dose of thyrotropin (TSH, 500 mU) induced a slight increase in thyroidal tissue levels of cyclic adenosine monophosphate (cAMP) while TSH 50 mU i.v. had no effect on cAMP levels. On the other hand both doses of TSH stimulated exocytosis, signified by a decrease in the number of exocytotic vesicles and endocytosis, signified by the appearance of pseudopods and colloid droplets. Selective thyroid infusion of dbcAMP (5 mM) or forskolin (25 microM), which induced a 10-fold increase in thyroid cAMP levels, did not induce any morphological sign of exocytosis or endocytosis in the follicle cells. The morphological response to TSH given i.v. was quantitatively unaltered by simultaneous infusion of forskolin. In contrast to the findings in rats, infusion of forskolin and dbcAMP in mice induced endocytosis. In conclusion, our findings in the mouse are in agreement with earlier studies in this and other species, indicating that cAMP mediates the effects of TSH on endocytosis and probably also on exocytosis. In contrast, our observations in the rat thyroid in vivo lead to the conclusion that cAMP is not the main intracellular mediator of exocytosis and endocytosis in this species. This conclusion is at variance with previous reports, mostly from in vitro studies.(ABSTRACT TRUNCATED AT 250 WORDS)
采用一种新开发的灌注技术，在经甲状腺素处理的大鼠和小鼠中研究了福斯高林和二丁酰环磷腺苷（dbcAMP）对甲状腺滤泡细胞胞吐作用和内吞作用的体内效应。反应物通过甲状腺上动脉选择性地灌注到一侧甲状腺叶。对侧叶作为对照。在大鼠中，静脉注射超最大剂量的促甲状腺激素（TSH，500 mU）会使甲状腺组织中环磷酸腺苷（cAMP）水平略有升高，而静脉注射50 mU的TSH对cAMP水平无影响。另一方面，这两种剂量的TSH均刺激胞吐作用，表现为胞吐小泡数量减少；刺激内吞作用，表现为伪足和胶体小滴的出现。选择性向甲状腺灌注dbcAMP（5 mM）或福斯高林（25 microM）可使甲状腺cAMP水平升高10倍，但未在滤泡细胞中诱导出任何胞吐或内吞的形态学迹象。同时灌注福斯高林并不会改变静脉注射TSH后的形态学反应。与在大鼠中的发现相反，在小鼠中灌注福斯高林和dbcAMP会诱导内吞作用。总之，我们在小鼠中的发现与该物种及其他物种早期的研究结果一致，表明cAMP介导TSH对内吞作用的影响，可能也介导对胞吐作用的影响。相比之下，我们在大鼠甲状腺体内的观察结果得出结论，cAMP不是该物种胞吐作用和内吞作用的主要细胞内介质。这一结论与之前大多来自体外研究的报道不一致。（摘要截短至250字）
