DEVELOPMENTAL-CHANGES IN THE BASEMENT-MEMBRANE OF THE NORMAL AND HYPOTHYROID POSTNATAL RAT TESTIS - SEGMENTAL LOCALIZATION OF FIBULIN-2 ANDFIBRONECTIN

To characterize developmental changes in the extracellular matrix of t he postnatal rat testis in relationship to the timing of germ cell mat uration, we immunolocalized fibulin-1, fibulin-2, and other matrix com ponents in the testes of normal and propylthiouracil (PTU)-induced hyp othyroid animals. Unlike laminin, nidogen, and perlecan, which were pr esent in the seminiferous tubule basement membrane (BM) throughout pos tnatal development, fibulins were found to disappear from the postnata l tubule BM. Fibulin-1 was no longer detected after Day 5 whereas fibu lin-2 became localized in a segmental manner within the PM of each sem iniferous tubule on Days 10 and 15 and disappeared by Day 20. Fibronec tin showed a segmental pattern in the level of immunostaining of the t ubule BM on Days 10 and 15, with a more uniform staining seen at earli er and later ages. Collagen VI was initially confined to the interstit ial matrix in the Day 5 testis and became progressively more closely a ssociated with the seminiferous tubule BM at later stages. The disappe arance of fibulin-2 and the BM-association of collagen VI were both de layed in the PTU-treated testes. The developmental changes in the stai ning patterns for fibulin-2 and fibronectin coincide with the adhesion and alignment of peritubular cells on the inner seminiferous tubule B M. The delay in maturation of the seminiferous tubule BM in the testes of PTU-treated rats demonstrates a correlation between changes in the composition of the tubule BM and cellular development of the testis.