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Proteinase and proteinase-inhibitor activities of rat uterine myometrium during pregnancy and involution.

ABSTRACT: A supernatant fraction was prepared from rat uterine myometrium by homogenization, sonication and centrifugation. In this supernatant the protein concentration and the activities of an acid proteinase, an acid phosphatase and a proteinase inhibitor were measured. From the fibrous sediment, after washing with 0.5% Triton X-100 and with water, an actomyosin-containing solution was obtained by extraction with 0.6M-NaCl, and in this extract the protein concentration and a neutral proteinase activity were measured. The myometrial wet weight and the activities of the acid proteinase, acid phosphatase and proteinase inhibitor increased by factors of 3-15 during pregnancy and decreased to the same or a greater extent during involution. The amount of protein extracted with 0.6M-NaCl increased by a factor of only 2.3 and the neutral proteinase activity remained essentially constant during pregnancy and involution. The pH optimum of the neutral proteinase, and its pattern of activity compared with those of the lysosomal enzymes, show that the neutral proteinase is not of lysosomal origin. Actomyosin is degraded by the neutral proteinase activity in vitro. Since actomyosin is rapidly broken down only after parturition, the action of the neutral proteinase activity on actomyosin, if this occurs in vivo, must be regulated in some way. The proteinase-inhibitor activity measured in the first supernatant varied in a manner which suggested that it could be involved in this control.

SUBMITTER: Afting EG

PROVIDER: S-EPMC1186343 | biostudies-other | 1979 Jan

REPOSITORIES: biostudies-other

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Project description:BACKGROUND: Myometrial growth and remodeling of the cytoskeleton and focal adhesions during late pregnancy may be critical aspects of myometrial activation and thus labour. Yet our understanding of these aspects is inhibited by the paucity of information concerning the components of focal adhesions in the myometrium. The focal adhesion protein hydrogen peroxide-inducible clone-5 (Hic-5) has recently been found in mononuclear smooth muscle but was not examined in the myometrium during pregnancy. Thus, the goal of this study was to characterize Hic-5 mRNA and protein expression in the rat myometrium during pregnancy and labour. METHODS: Rat myometrium samples were obtained from non-pregnant animals, pregnant animals on days (d) 6, 12, 15, 17, 19, 21, 22, 23 (active labour) and 1 day postpartum (PP). In addition, myometrium samples were collected from rats within a progesterone-delayed labour paradigm. Hic-5 mRNA expression was analyzed by Northern blot analysis while Hic-5 protein expression was examined by immunoblot and immunofluorescence analysis. RESULTS: Hic-5 mRNA expression on d15, d19 and d21 was found to be significantly elevated compared to d6 and d12 of pregnancy and expression on d23 was significantly elevated over d6 (p < 0.05). Immunofluorescence analysis demonstrated that detection of Hic-5 protein in the circular muscle layer appeared to increase from d17 onwards, except PP, and Hic-5 was detectable in the cell cytoplasm and more continuously associated with myometrial cell membranes. In the longitudinal muscle layer Hic-5 was readily detectable by d15 and thereafter and primarily associated at myometrial cell membranes. Co-immunofluorescence analysis of potential Hic-5 and focal adhesion kinase (FAK) association in situ demonstrated a limited level of co-localization on d19, d23 and PP in the circular muscle layer while in the longitudinal muscle layer Hic-5 and FAK were readily co-localized at myometrial cell membranes. CONCLUSION: Hic-5 is highly expressed in the rat myometrium during late pregnancy and labour and co-localizes with FAK in situ. Our results are consistent with a potential role for Hic-5 in focal adhesion remodeling in the rat myometrium during late pregnancy.

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Proteinase and proteinase-inhibitor activities of rat uterine myometrium during pregnancy and involution.

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