Regulation by thyroid hormone of the expression of basement membrane components in rat prepubertal Sertoli cells

ABSTRACT The present study reports the modulation of basement membrane (BM)components,laminin,entactin,andtypeIVcollagen,expression in prepubertal rat Sertoli cell by the thyroid hormone T3. Immunocytochemical studies of permeabilized Sertoli cells in culture showed that T3 treatment (10 7 M for 24 h) increased the number of cells stainingpositiveforlamininand/orentactin(from58 5.3%to86.4 6.5%, P 0.01). In contrast, a strong inhibition of type IV collagen immunopositivity was observed. Western blot analysis of Sertoli cellconditionedmediaindicatedthatT3treatmentsignificantly(P 0.01) increased the level of secreted entactin by 60±65% without affecting the levels of laminin A and B1/B2 chains. Moreover, thyroid hormone treatment of Sertoli cells significantly reduced type IV collagen secretion by 62% (P 0.05). Slot blot analysis of poly-A RNA demonstrated a significant (P 0.01) increase in the level of entactin messenger RNA(mRNA)by140%(P 0.01)anda50%reductionoftype IV collagen 1 chain mRNA after thyroid hormone treatment. No effect of thehormonewasobservedontheaccumulationofthelaminin B1andB2chainmRNAsinSertolicell cultures. These effects cannot be ascribed to changesinthedegradationofBMcomponents,because no effect of thyroid hormone was observed on plasminogen activators or metalloproteinase secretion by Sertoli cells. These observations indicate the Sertoli cell as a source of entactin within the testis, demonstrate the ability of T3 to differentially regulate theexpressionofBMcomponents,andcanberegardedasapart of the integrated mechanism by which thyroid hormone affects testicular development and differentiation