- 06-12-2006, 04:41 PM
I stumbled across this searching for AR agonists, but it seams promising.
-ADRENERGIC RECEPTOR POPULATION IS UP-REGULATED IN CHICKEN SKELETAL MUSCLE CELLS TREATED WITH FORSKOLIN. K.Y. Bridge, R.B. Young, and J.R. Vaughn. Marshall Space Flight Center, ES76, Huntsville, AL.
Skeletal muscle hypertrophy is promoted by in vivo administration of -adrenergic receptor ( AR) agonists. These compounds presumably exert their physiological action through the AR, and alterations in the population of AR could potentially change the ability of the cell to respond to the AR agonists. Since the intracellular chemical signal generated by the AR is cyclic AMP (cAMP), experiments were initiated in primary chicken muscle cell cultures to determine if artificial elevation of intracellular cAMP by treatment with forskolin would alter the population of functional AR expressed on the surface of muscle cells. Chicken skeletal muscle cells after 7 days in culture were employed for the experiments because muscle cells have attained a steady state with respect to muscle protein metabolism at this stage. Cells were treated with 0-10 µM forskolin for a total of three days. At the end of the 1, 2, and 3 day treatment intervals, the concentration of cAMP and the AR population were measured. Receptor population was measured in intact muscle cell cultures as the difference between total binding of [3H]CGP-12177 and non-specific binding of [3H]CGP-12177 in the presence of 1 µM propranolol. Intracellular cAMP concentration was measured by radioimmunoassay. The concentration of cAMP in forskolin-treated cells increased up to 10-fold in a dose dependent manner. Increasing concentrations of forskolin also led to an increase in AR population, with a maximum increase of approximately 50% at 10 µM. This increase in AR population was apparent after only 1 day of treatment, and the pattern of increase was maintained for all 3 days of the treatment period. Thus, increasing the intracellular concentration of cAMP leads to up-regulation of AR population. The effect of forskolin on the quantity and apparent synthesis rate of the heavy chain of myosin (mhc) were also investigated. A maximum increase of 50% in the quantity of mhc was observed at 0.2 µM forskolin, but higher concentrations of forskolin reduced the quantity of mhc back to control levels.
- 06-12-2006, 04:45 PM
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.
02-23-2007, 04:06 PM
Interesting looking at who conducted the study. I bet this is basic research on ways for astronauts to maintain muscle mass during long space flights.
02-23-2007, 10:48 PM
I heard in space that astronauts can bench well over 1000 lbs. Now we know their secret Interesting studies but they're talking about adrenergic receptors not androgen receptors.
02-23-2007, 11:03 PM
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