Capriani A, Chiavegato A, Franch R, Azzarello G, Vinante O, Sartore S
Department of Biomedical Sciences, University of Padua, Italy.
J Muscle Res Cell Motil. 1997 Aug;18(4):413-27. doi: 10.1023/a:1018642713934.
Ovarectomized rabbits displayed a decreased SM1 to SM2 ratio of smooth muscle-type myosin heavy chain isoforms compared to unoperated, virgin females which was reversed after 17beta-oestradiol administration to a value similar to that of control animals. When this steroid was given to sexually immature animals or to adult virgin rabbits, SM2 expression was not induced, as also happened with proliferating myometrial smooth muscle cells grown in vitro. In growing rabbit, the 17beta-oestradiol administration induced the formation of the circular and the longitudinal muscle layers, characteristics of sexually competent females. The SM2 isoform was up-regulated during postnatal development and the SM1 to SM2 ratio changed during pregnancy and post-partum period but not with human gonadotropin treatment which increases the level of circulating progesterone. Immunofluorescence staining of adult myometrium with anti-SM2 antibody indicated that this isoform is localized to the longitudinal layer exclusively and, in contrast to the circular layer, its expression was independent of oestrogen level. Difference in oestrogen sensitivity between the two layers was also detected for the expression of the intermediate filament protein vimentin and the thin filament protein calponin. Changes of SM2 expression in the myometrium correlated with variations in the oestrogen receptor density as also confirmed by decreased SM2 content/oestrogen receptor density in the circular layer when ovarectomized females were treated with the oestrogen antagonist ICI 182,780. Our results indicate that: (1) a specific distribution of myosin heavy chain exists within rabbit myometrium, and (2) SM2 myosin expression in this smooth muscle is under oestrogen control.
与未手术的未孕雌性相比，去卵巢兔平滑肌型肌球蛋白重链同工型的SM1与SM2比值降低，而给予17β-雌二醇后该比值逆转，达到与对照动物相似的值。当将这种类固醇给予性未成熟动物或成年未孕兔时，未诱导出SM2表达，体外培养的增殖子宫肌层平滑肌细胞也出现这种情况。在生长中的兔中，给予17β-雌二醇可诱导形成环形和纵形肌层，这是性成熟雌性的特征。SM2同工型在出生后发育过程中上调，在怀孕和产后期间SM1与SM2比值发生变化，但人绒毛膜促性腺激素治疗（可提高循环孕酮水平）时未发生变化。用抗SM2抗体对成年子宫肌层进行免疫荧光染色表明，该同工型仅定位于纵形肌层，与环形肌层相反，其表达与雌激素水平无关。对于中间丝蛋白波形蛋白和细肌丝蛋白钙调蛋白的表达，也检测到两层之间雌激素敏感性的差异。子宫肌层中SM2表达的变化与雌激素受体密度的变化相关，当去卵巢雌性用雌激素拮抗剂ICI 182,780处理时，环形肌层中SM2含量/雌激素受体密度降低也证实了这一点。我们的结果表明：（1）兔子宫肌层中存在肌球蛋白重链的特定分布，（2）这种平滑肌中SM2肌球蛋白的表达受雌激素控制。
