Expression of nerve growth factor (NGF) isoforms in the rat uterus during pregnancy: accumulation of precursor proNGF.
The mechanisms that promote the transient degenerative changes in the uterus innervation during pregnancy remain incompletely understood. Signaling by the nerve growth factor (NGF)-beta is important for maintaining the density of peripheral sympathetic innervation. Here, we analyzed the spatial and temporal expression of NGF isoforms in the rat uterus using RT-PCR, immunoblot analysis, and immunohistochemistry during pregnancy (d 7, 14, and 21), and postpartum (d 1, 8, and 22). Western blot analysis using antibodies to mature NGF-beta and to proNGF domain demonstrated a significant decrease in mature NGF-beta at gestational d 14 and 21 (term pregnancy) and 1 d postpartum, which paralleled a remarkable accumulation of the 26-28-, 32-, and 60-kDa proNGF forms. There were diminished ratios of mature NGF-beta to proNGF independent of uterus growth on the same gestational days. Immunohistochemistry revealed a progressive NGF-beta decline throughout pregnancy in the myometrium and a near absence at term pregnancy, which contrasted with increased NGF immunostaining in the intermyometrial connective tissue layers. More importantly, proNGF-specific antibodies identified the increased NGF immunoreactivity in the intermyometrial layers at term pregnancy as proNGF and not mature NGF-beta. Alterations in the processing of NGF and accumulation of proNGF in the intermyometrial layers, where axonal degeneration occurs, may contribute significantly to the pregnancy-related uterine denervation and to the control of myometrial activity.
Lobos
Edgar
E
Institute of Anatomy, University of Leipzig, Liebigstrasse 13, 04103 Leipzig, Germany. Edgar.Lobos@medizin.uni-leipzig.de
Gebhardt
Claudia
C
Kluge
Annett
A
Spanel-Borowski
Katharina
K
D000818:Animals; D005260:Female; D007150:Immunohistochemistry; D020932:Nerve Growth Factor / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D049590:Postpartum Period / Q000378:metabolism; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D020033:Protein Isoforms; D011498:Protein Precursors / Q000032:analysis / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011917:Rats, Inbred Lew; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014599:Uterus / Q000737:chemistry* / Q000378:metabolism
D020033:Protein Isoforms; D011498:Protein Precursors; D012333:RNA, Messenger; D020932:Nerve Growth Factor