Immediate cell signal induced by laminin in rat Sertoli cells

Rat Sertoli cells in primary culture have been studied for their ability to respond to extracellular matrix macromolecules by increases of [Ca2+](i). We observed that cells seeded oil glass coverslips, loaded with the intracellular Ca2+ indicator fura-2, responded to laminin, but nut to fibronectin, with an immediate [Ca2+](i) raise, with a peak followed by a prolonged plateau. [Ca2+](i) increases were dependent upon Ca2+ influx across the plasma membrane and Ca2+ release from intracellular Ca2+ pools. Ca2+ influx was inhibited by extracellular Ca2+ removal by EGTA, and by treatment with La3+, or with the L-type voltage operated Ca2+ channel blocker, nifedipine. Ca2+ release from intracellular Ca2+ storing organelles, was inhibited by the microsomal Ca2+-ATPase blocker thapsigargin. Responses were mimicked by synthetic peptides carrying the Arg-Gly-Asp adhesion sequence, but not by the control Arg-Gly-Glu-containing peptide, in which aspartic acid was replaced by glutamic acid. Laminin-dependent [Ca2+](i) increases were down-regulated by the follicle-stimulating hormone. However, this occurred only when cells were not subjected to homotypic cell-cell contact, and responded to the hormone with a significant [Ca2+](i) elevation. These results indicate that laminin may regulate Sertoli cells by intracellular signals that perturb Ca2+ homeostasis. This role may be related to an effect exerted by the seminiferous epithelium basement membrane on the regulation of spermatogenesis. (C) 2000 Elsevier Science B.V./International Society of Matrix Biology. All rights reserved.