Earlier studies have shown that germ cells or germ cell-conditioned media are capable of regulating α₂-macroglobulin (α₂-MG, a non-specific protease inhibitor) expression by Sertoli cells and hepatocytes cultured in vitro. These results illustrate a possible physiological link between testes and liver regarding α₂-MG production. Using a series of surgical procedures including castration, hemicastration, and hepatectomy coupled with Northern blot and immunoblot analyses, we report herein that the surge in α₂-MG expression in the liver in response to inflammation is indeed regulated, at least in part, by the testis via testosterone. It was found that hepatectomy induced at least a tenfold increase in the steady-state mRNA and protein production of α₂-MG in the liver. However, castration induced a mild but not statistically significant induction of α₂-MG in the liver in contrast to sham operation or hemicastration alone, when hemicastration alone could induce liver α₂-MG production by almost fourfold. Perhaps most important of all, hepatectomy accompanied by castration significantly reduced the liver α₂-MG response to the surgery-induced inflammation compared with hepatectomy alone, illustrating that the removal of the testicles can induce a loss of signal communications between the testis and the liver, rendering a significant loss of the α₂-MG response to experimentally induced inflammation in the liver. Interestingly, this lack of response of the liver to surgery-induced inflammation regarding α₂-MG production following castration could be restored, at least in part, by using testosterone implants placed subdermally 6 days prior to orchiectomy. Collectively, these results illustrate that a physiological link does indeed exist between the testis and the liver, and that testes per se can influence the liver in vivo α₂-MG expression in response to inflammation possibly via testosterone or testosterone-induced biological factor(s).

The timely restructuring of the blood–testis barrier (BTB) that facilitates the migration of preleptotene and leptotene spermatocytes from the basal to the adluminal compartment in the seminiferous epithelium of adult rat testes, which occurs at late stage VII through early stage VIII of the epithelial cycle, is a crucial cellular event of spermatogenesis. However, the regulation of BTB dynamics at the biochemical level remains elusive. In this study, tumor necrosis factor α (TNFα), a secretory product of Sertoli and germ cells in rat testes, was shown to affect junction dynamics in vivo. Following an acute administration of recombinant TNFα directly to adult rat testes in vivo at 0.5 and 2 μg/testis (with a body weight ~300 g), this treatment significantly and transiently disrupted the BTB. It also transiently inhibited the steady-state protein levels of occludin, zonula occludens-1, and N-cadherin, but not junction adhesion molecule-A, α-, and β-catenin in testes at the BTB site as illustrated by immunoblottings, immunohistochemistry, electron microscopy, and fluorescent microscopy. This transient disruption of the BTB integrity induced by TNFα treatment was further demonstrated by a functional test to assess the passage of a fluorescent dye (e.g. fluorescein-5-isothiocyanate) from the systemic circulation to the adluminal compartment. Additionally, both the phosphorylated-Ser/Thr protein kinase activated by MAP kinase kinase (p-p38) and phosphorylated-externally regulated kinase (p-ERK) mitogen -activated protein kinase-signaling pathways were transiently activated. Collectively, these data coupled with the recently published in vitro studies have illustrated that the BTB is likely utilizing a novel mechanism in which localized production of TNFα by Sertoli and germ cells into the microenvironment at the basal compartment facilitates the timely restructuring (‘opening’?) of the BTB during spermatogenesis to facilitate germ cell migration.