Regulated Assembly of Connexin33 and Connexin43 into Rat Sertoli Cell Gap Junctions1

Abstract

Immunofluorescence and immunogold electron microscopy were employed to examine the assembly of connexins (Cx) 33, 37, and 43 into testis cell gap junctions in mature and postnatal rats. Cx37 was localized by immunofluorescence to the endothelia of blood vessels in both mature and immature testes and was not further characterized. Only Cx43 assembled into Leydig cell gap junctions, but Cx43 also co-assembled with Cx33 in some Sertoli-Sertoli gap junction plaques within and near Sertoli occluding junctions and on adluminal surfaces Assembly of Sertoli gap junctions appeared to be regulated according to the stage of the seminiferous epithelium since Cx33 (and Cx43) immunoreactivity was strong in Sertoli cells from stages II-VII but weak in stages IX-XIV. During postnatal maturation, assembly of Cx33 into gap junctions was regulated independently of Cx43 assembly. Cx43 was present on Sertoli cells of all tubules from postnatal Day 5 through Day 28. In contrast, Cx33 was not apparent on Sertoli cell surfaces until Day 15 and gradually accumulated in all tubules through Day 28. Between postnatal Days 38 and 43, the immunoreactivities of Cx33 and Cx43 became weak in Sertoli cells containing step 9-14 elongated spermatids. Thus, connexin abundance and gap junction composition in Sertoli cells is regulated during testis maturation and the cycle of the seminiferous epithelium.

Expression and regulation of connexin43 in rat Leydig cells

“…Cx26 and Cx32 were localized faintly in the apical region of the seminiferous epithelium (Risley et al 1992). Cx37 is localized in the endothelia of blood vessels, whereas only Cx43 is localized in the membrane appositions between Leydig cells and in some Sertoli-Sertoli gap junctions (Tan et al 1996). Expression of Cx43 in Leydig cells increases with age and reaches maximum levels of expression in the adult (Risley et al 1992), which is consistent with the idea that gap junctional communication is involved in the control of hormone secretion.…”

“…A total of 13 mammalian gap junction proteins, known as connexins, have been cloned (Goodenough et al 1996, Kumar & Gilula 1996. Five of these have been identified in the rat testis (Kadle et al 1991, Risley et al 1992, Tan et al 1996. Cx33 and Cx43 are expressed in Sertoli cells in a stage-and age-dependent manner (Risley et al 1992).…”

“…Using purified Leydig cell preparations, we found in the present study that Cx43 is expressed in 20-day-old rat Leydig cells and reaches a plateau by day 40. Tan et al (1996) reported that Cx43 in the intersitium was localized predominantly to Leydig cell gap junctions. In the tubules, Cx43 was distributed in linear arrays at the periphery of tubules, between the basal and adluminal compartments, and in the region containing the Sertoli occluding junctions.…”

“…Immunocytochemical studies have shown that Cx43 assembles gap junctions between Leydig cells (Risley et al 1992, Pellitier 1995, Tan et al 1996.…”

Expression of Connexin43 in mouse Leydig, Sertoli, and germinal cells at different stages of postnatal development

“…A specific spatial distribution has been found for Cx26, Cx31, Cx32, Cx33 and Cx43 using IF studies in testis from adult animals (Batias et al, 1999;Mok et al, 1999;Pérez-Armendariz et al, 1994;Pelletier, 1996;Risley et al, 1992;Tan et al, 1996). Several lines of evidences support the idea that Cx43 is required for adequate control of fertility.…”