BACKGROUND: The secretory activity of Sertoli cells (SC) is dependent on ion 
channel functions and protein synthesis and is critical to ongoing 
spermatogenesis. The aim of this study was to investigate the mechanism of 
action associated with a non-metabolizable amino acid [14C]-MeAIB 
(alpha-(methyl-amino)isobutyric acid) accumulation stimulated by T4 and the role 
of the integrin receptor in this event, and also to clarify whether the T4 
effect on MeAIB accumulation and on Ca2+ influx culminates in cell secretion.
METHODS: We have studied the rapid and plasma membrane initiated effects of T4 
by using 45Ca2+ uptake and [45C]-MeAIB accumulation assays, respectively. 
Thymidine incorporation into DNA was used to monitor nuclear activity and 
quinacrine to analyze the secretory activity on SC.
RESULTS: The stimulation of MeAIB accumulation byT4 appears to be mediated by 
the integrin receptor in the plasma membrane since tetrac and RGD peptide were 
able to nullify the effect of this hormone. In addition, T4 increases 
extracellular Ca2+ uptake and Ca2+ from intracellular stocks to enhance nuclear 
activity, but this genomic action seems not to influence SC secretion mediated 
by T4. Also, the cytoskeleton and CIC-3 chloride channel contribute to the 
membrane-associated responses of SC.
CONCLUSIONS: T4 integrin receptor activation ultimately determines the plasma 
membrane responses on amino acid transport in SC, but it is not involved in 
calcium influx, cell secretion or the nuclear effect of the hormone.
GENERAL SIGNIFICANCE: The integrin receptor activation by T4 may take a role in 
plasma membrane processes involved in the male reproductive system.