Agreed..
Still, something about this just still doesn’t sit well with me in regards to the process of skeletal muscle proliferation...
EFFECTS ON CELL PROLIFERATION
Polyamines such as putrescine, spermidine and spermine are essential for normal DNA replication, cell proliferation and cell migration. Their production is tightly regulated, par- ticularly via the rate-limiting enzyme, ornithine decarboxylase (22,31,43,70). Polyamine depletion results in growth arrest (4). As indicated earlier, agmatine interferes with polyamine biosynthesis via induction of antizyme, which induces the degradation of orni- thine decarboxylase and suppresses polyamine transporters but, alternatively, can be con- verted to putrescine through the actions of agmatinase (Fig. 2). Normally, proteins will be degraded after attachment of ubiquitin, but a small number of proteins, including ornithine decarboxylase, are handled differently. This enzyme is targeted for destruction by another protein antizyme (13,74). Therefore, it is tempting to speculate that the regulation of the half-life of ornithine decarboxylase protein is important and that this enzyme is tightly and specifically regulated. Agmatine (4 mmolGL) induces the expression of functional anti- zyme by an agmatine-dependent translational frameshift of antizyme mRNA to produce a full-length protein (62), resulting in a depletion of intracellular polyamines leading to sup- pression of cellular proliferation (52). In addition, agmatine depletes cells of polyamines by interacting with another enzyme involved in polyamine metabolism, spermidineGsper- mine acetyltransferase (SSAT). Agmatine increases the synthesis of this rate-limiting en- zyme of the interconversion pathway between polyamines (0.5 mmolGL) (71). Increased SSAT activity by agmatine is accompanied by depletion of spermidine and spermine, and accumulation of putrescine and N1-acetylspermidine (71). The authors concluded that the depletion of spermidine and spermine causes the inhibition of cell growth, although the el- evated putrescine levels do not fit in this scheme since putrescine would normally promote cell proliferation (52,55). However, agmatine may also inhibit cell proliferation by com- pletely different mechanisms involving the inhibition of polyamine transport into cells (5,8). Another possible pathway by which agmatine may alter cell proliferation is by binding to I2 receptors (53,55), especially since the I2 agonist idazoxan potently inhibits vascular smooth muscle cell growth (55), although agmatine has a lower affinity for I2 binding sites.
Taken together, these findings suggest that agmatine may inhibit cellular proliferation by several different mechanisms, such as inhibition of polyamine transport into cells, induction of antizyme and inhibition of ODC, stimulation of I2 binding sites as well as an in-duction of SSAT activity. It is not clear which of these possible mechanisms plays a leading role or whether a combination of different mechanisms is involved.
Moreover, as with the effects of agmatine described earlier high concentrations (up to 1 mmolGL) (52) are necessary to inhibit cell proliferation. It is not clear whether agmatine is normally present in any tissue at sufficiently high levels to inhibit cell proliferation in vivo.
http://onlinelibrary.wiley.com/store/10.1111/j.1527-3466.2004.tb00128.x/asset/j.1527-3466.2004.tb00128.x.pdf?v=1&t=jcr4vr8s&a0146a51
Honestly, I have no idea what concentrations of 1 mmolGL could possibly equate to, but this excerpt is more along the lines of why I question the use of agmatine in bodybuilding..
