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 [Ca(2+)](i). We observed that cells seeded on glass coverslips, loaded with the intracellular Ca(2+) indicator fura-2, responded to laminin, but not to fibronectin, with an immediate [Ca(2+)](i) raise, with a peak followed by a prolonged plateau. [Ca(2+)](i) increases were dependent upon Ca(2+) influx across the plasma membrane and Ca(2+) release from intracellular Ca(2+) pools. Ca(2+) influx was inhibited by extracellular Ca(2+) removal by EGTA, and by treatment with La(3+), or with the L-type voltage operated Ca(2+) channel blocker, nifedipine. Ca(2+) release from intracellular Ca(2+) storing organelles, was inhibited by the microsomal Ca(2+)-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 [Ca(2+)](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 [Ca(2+)](i) elevation. These results indicate that laminin may regulate Sertoli cells by intracellular signals that perturb Ca(2+) homeostasis. This role may be related to an effect exerted by the seminiferous epithelium basement membrane on the regulation of spermatogenesis.