Amino Acid Uptake and Protein Synthesis in Rat Testes: Stimulation by Dissociable Factors

Abstract

Low concentration (25 mM) of sodium in the incubation medium produced a decrease in the amino acid uptake by the testis tissue as well as a reduction in the response to FSH. In this experimental condition, the basal protein synthesis and the stimulatory effect of FSH was not modified. The subcutaneous administration of testosterone to 15 day old rats increased the protein synthesis in the testis without any modification in the amino acid uptake. The addition of DBcAMP (1 mM) or glucose (14 mM) to the incubation medium increased the protein synthesis in the testes of immature (12 day-old) or prepubertal (32 day-old) rats respectively. The amino acid uptake was not modified. In immature rat testes, with protein synthesis completely inhibited by cycloheximide, the restoration of the sodium concentration in the incubation medium to normal levels produced an increase in amino acid uptake. The results above seem to indicate that protein synthesis and amino acid uptake in rat testes tissue can be regulated, at least partially, by different factors.

Pertussis toxin nullifies the depolarization of the membrane potential and the stimulation of the rapid phase of 45Ca2+ entry through L-type calcium channels that are produced by follicle stimulating hormone in 10- to 12-day-old rat Sertoli cells

“…This FSH stimulatory action was independent of its effect on AC-cAMP activity and was observed using FSH from different species and sources (NHPP: ovine, porcine, and rat; Sigma-Aldrich: ovine) (Irusta and Wassermann, 1974; Pérez-Sánches and Wassermann, 1981; Cruz Curte and Wassermann, 1985; Spritzer and Wassermann, 1985; Silva and Wassermann, 1999; Silva et al, 2002). …”

Diverse FSH and Testosterone Signaling Pathways in the Sertoli Cell

“…The former is dependent on the AC-cAMP-PKA-cAMP response element binding protein (CREB) pathway. The latter is regulated by the Ca 2 + -dependent (L-type VDCC) Na + -amino acid cotransport pathway, which is blocked by verapamil, Co 2 + , and Ni 2 + [13,14,24] , but not affected by dbcAMP, exogenous cAMP, or a cholera toxin-induced increase of intracellular cAMP [7,23,47] . This binary regulatory mechanism is active up to approximately 25 days of age.…”