Elastomeric isoprene rubber compositions contain an effective amount of a coupling system (A) as an inorganic filler/elastomer coupling agent, and (B) at least one natural or synthetic rubber elastomer, (C) an inorganic filler as reinforcing filler, (D) other conventional constituents or additives comprising (a) vulcanization agent(s), the coupling system (A) being a particular mixture of the following combination of constituents (A1) and (A2): (A1) is at least one coupling agent selected from among the following functionalized organosilicon compounds of formula (I):[(G0)3SiO1/2]m[(G0)2SiO2/2]n[G0SiO3/2]o[SiO4/2]p[(G2)a(G1)a′(Z—CO—N═N—CO-A)SiO(3-a-a′)/2]g and (A2) is at least one coating agent for the reinforcing filler including one compound with the single function Y in the structure thereof which is capable of bonding physically and chemically to the inorganic filler and resulting in an increase in dispersion of the charge within the rubber matrix and a reduction in viscosity of the composition.