Wise Young
07-31-2003, 08:39 AM
• Estrada M, Espinosa A, Muller M and Jaimovich E (2003). Testosterone stimulates intracellular calcium release and mitogen-activated protein kinases via a g protein-coupled receptor in skeletal muscle cells. Endocrinology 144:3586-97. Summary: Involvement of intracellular Ca(2+) and ERK1/2 phosphorylation in the fast nongenomic effects of androgens in myotubes was investigated. Testosterone or nandrolone produced fast (<1 min) and transient increases in intracellular Ca[2+) with an oscillatory pattern. Calcium signals were slightly reduced in Ca[2+)-free medium, but lack of oscillations was evident. Signals were blocked by U-73122 and xestospongin B, inhibitors of inositol 1,4,5-trisphosphate [IP[3)) pathway. Furthermore, IP[3) increased transiently 2- to 3-fold 45 sec after hormone addition. Cyproterone neither affected the fast Ca[2+) signal nor the increase in IP[3). Calcium increases could also be induced by the impermeant testosterone conjugated to BSA, and the effect of testosterone was abolished in cells incubated with guanosine 5'-O-[2-thiodiphosphate) or pertussis toxin. Stimulation of myotubes with testosterone, nandrolone, or testosterone conjugated to BSA increased immunodetectable phosphorylation of ERK1/2 within 5 min, and this effect was not inhibited by cyproterone. Phosphorylation was blocked by the use of 1,2-bis[2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethylester, U-73122, and xestospongin B as well as by dominant negative Ras, MAPK kinase [MEK), or the MEK inhibitor PD-98059. In addition, guanosine 5'-O-[2-thiodiphosphate) or pertussis toxin blocked ERK1/2 phosphorylation. These results are consistent with a fast effect of testosterone, involving a G protein-linked receptor at the plasma membrane, IP[3)-mediated Ca[2+) signal, and the Ras/MEK/ERK pathway in muscle cells. Centro de Estudios Moleculares de la Celula and Instituto de Ciencias Biomedicas, Facultad de Medicina, Universidad de Chile, Casilla 70005, Santiago 6530499, Chile.