title: Monoclonal antibodies specific for rat relaxin. X. Endogenous relaxin induces changes in the histological characteristics of the rat vagina during the second half of pregnancy.
abstract: This study employed morphometric analysis to evaluate changes in the histological characteristics that accompany relaxin-induced growth and softening of the vagina during the second half of rat pregnancy. There were three treatment groups (N = 4/group). Five milligrams of a monoclonal antibody for rat relaxin, designated MCA1, were injected i.v. daily on days 12-21 of gestation to treatment group MCA1. Control groups received either 5 mg of monoclonal antibody for fluorescein (MCAF; monoclonal antibody control) or 0.5 ml PBS (vehicle control). Vaginas were removed on day 22 of pregnancy, fixed in 10% neutral-buffered formalin, and embedded in paraffin. Tissue sections (5 microm) were stained with Gomori's trichrome to visualize collagen, or orcein to visualize elastin. Measurements were performed with a light microscope equipped with a video camera connected to a computer. Within the vaginal stroma, the density of collagen fiber bundles was lower, the length of elastin fibers was shorter, and the cross-sectional area and wall thickness of arteries were greater in relaxin-replete control rats than in relaxin-deficient MCA1-treated rats. These relaxin-induced changes in the stroma appear to account, at least in part, for the hormone's softening effect on the vagina. Within the epithelium, there were approximately 2-fold more basal and mucus-secreting cells in relaxin-replete control rats than in MCA1-treated rats. The relaxin-induced accumulation of epithelial cells appears to contribute to vaginal growth. We conclude that relaxin plays a role in preparing the vagina as well as the cervix for rapid and safe delivery in pregnant rats.
authors.affiliation: Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana 61801, USA.
authors.forename: S
authors.initials: S
authors.lastname: Zhao
authors.forename: O D
authors.initials: OD
authors.lastname: Sherwood
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D005260:Female; D005333:Fetus / Q000502:physiology; D006651:Histocytochemistry; D009929:Organ Size / Q000502:physiology; D016612:Paraffin Embedding; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012065:Relaxin / Q000276:immunology / Q000378:metabolism*; D014621:Vagina / Q000033:anatomy & histology / Q000378:metabolism* / Q000502:physiology
chemical_list: D000911:Antibodies, Monoclonal; D012065:Relaxin