Foud this also right after I posted.
seems to support.
doi: 10.1290/1071-2690(2000)036<0485:ARPIUR>2.0. CO;2
In Vitro Cellular & Developmental Biology - Animal: Vol. 36, No. 7, pp. 485–492.
-ADRENERGIC RECEPTOR POPULATION IS UP-REGULATED BY INCREASED CYCLIC ADENOSINE MONOPHOSPHATE CONCENTRATION IN CHICKEN SKELETAL MUSCLE CELLS IN CULTURE
RONALD B. YOUNG, KRISTIN Y. BRIDGE, and JEFFREY R. VAUGHN
Marshall Space Flight Center, Huntsville, Alabama 35812
Received 3 November 1999.
Accepted 7 December 1999.
Abstract—Skeletal muscle hypertrophy is promoted in vivo by administration of -adrenergic receptor (AR) agonists. Chicken skeletal muscle cells were treated with 1 M isoproterenol, a strong AR agonist, between days 7 and 10 in culture. AR population increased by approximately 40% during this treatment; however, the ability of the cells to synthesize cyclic adenosine monophosphate (cAMP) was diminished by twofold. Neither the basal concentration of cAMP nor the quantity of myosin heavy chain (MHC) was affected by the 3-d exposure to isoproterenol. To understand further the relationship between intracellular cAMP levels, AR population, and muscle protein accumulation, intracellular cAMP levels were artificially elevated by treatment with 0–10 M forskolin for 3 d. The basal concentration of cAMP in forskolin-treated cells increased up to sevenfold in a dose-dependent manner. Increasing concentrations of forskolin also led to an increase in AR population, with a maximum increase of approximately 40–60% at 10 M forskolin. A maximum increase of 40–50% in the quantity of MHC was observed at 0.2 M forskolin, but higher concentrations of forskolin reduced the quantity of MHC back to control levels. At 0.2 M forskolin, intracellular levels of cAMP were higher by approximately 35%, and the AR population was higher by approximately 30%. Neither the number of muscle nuclei fused into myotubes nor the percentage of nuclei in myotubes was affected by forskolin at any of the concentrations studied.