title: Maturational changes in connexin 43 expression in the seminiferous tubules may depend on thyroid hormone action.
abstract: BACKGROUND
  Connexin 43 (Cx43) mediates the effect of thyroid hormone on Sertoli cell maturation in vitro. We investigated the influence of triiodothyronine (T3) administration on Cx43 expression in relation to the progress in seminiferous tubule maturation.
  
  
  METHODS
  Male rats were daily injected with 100 µg T3/kg body weight from birth until postnatal day (pnd) 5 (transient treatment - tT3) or until pnd 15 (continuous treatment - cT3) or solvent - control (C). On pnd 16 serum hormone levels, body and testes weight, seminiferous tubule morphometry, Cx43 immunostaining and germ cell degeneration were investigated. Cx43 expression was also assessed in six 50-day-old adult untreated rats.
  
  
  RESULTS
  tT3 increased 2.6-fold serum level of T3, testes weight, and seminiferous tubule diameter, and induced maturation-like dislocation of Cx43 expression from the apical to the peripheral region of Sertoli cell cytoplasm. In addition, incidence of Cx43-positive tubules declined from 86% in C to 46% after tT3, being similar to the adult value (30% of tubules Cx43-positive). In turn, cT3 increased serum T3 level 12-fold, and decreased body weight. Seminiferous tubules became shortened and distended, Sertoli cell cytoplasm vacuolated, Cx43 expression had minimal intensity and germ cell degeneration increased.
  
  
  CONCLUSIONS
  Cx43 might intermediate a short and transient stimulatory effect of T3 on seminiferous tubule maturation that disappeared together with exposure to the toxic effect of a continuously high level of the hormone.
authors.affiliation: Department of Reproductive Endocrinology, Medical University of Lodz, Poland.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Marchlewska
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Kula
authors.forename: Renata
authors.initials: R
authors.lastname: Walczak-Jedrzejowska
authors.forename: Wojciech
authors.initials: W
authors.lastname: Kula
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Oszukowska
authors.forename: Eliza
authors.initials: E
authors.lastname: Filipiak
authors.forename: Tomasz
authors.initials: T
authors.lastname: Moszura
authors.forename: Jolanta
authors.initials: J
authors.lastname: Slowikowska-Hilczer
keywords: Cx43; Sertoli cells; germ cells; seminiferous tubule maturation