Posted by: Sergio
« on: February 01, 2013, 02:07:43 AM »From http://www.weightrainer.net/training/growth1.html, the one and only Casy Butt's web site.
When the sarcolemma (the muscle cell wall) is 'damaged' by tension (as in weight training or even stretching) growth factors are produced and released in the cell. There are several different types of growth factors. The most significant are:
Insulin-like Growth Factor 1 (IGF-1)
Fibroblast Growth Factor (FGF)
Transforming Growth Factor -Beta Superfamily (TGF-beta)
These growth factors can then leave the cell and go out into the surrounding area because sarcolemma permeabilty has been increased due to the 'damage' done during contraction. Once outside the muscle cell these growth factors cause the satellite cells to proliferate (mainly FGF does this) and differentiate (mainly IGF-1 does this). TGF-beta's role is one of mediation - in this case it inhibits growth. After this process the satellite cells then fuse with the muscle cells and donate their nuclei, giving the muscle cells the 'ability' to grow.
Now factors that promote protein synthesis such as IGF-1, growth hormone (GH), testosterone and some prostaglandins can commence the growth process. .....
IGF-1: IGF-1 comes in two varieties - paracrine IGF-1 is made primarily in the liver and autocrine IGF-1 is made locally in other cells. Paracrine IGF-1 travels through the bloodstream to the various tissues of the body, but autocrine IGF-1 is local in that in affects only tissues in the area in which it is released. Receptors on the surface of the cells are necessary for paracrine IGF-1 to enter the cells and exert its anabolic effects. But autocrine IGF-1, which is manufactured and released in the muscle cell as a response to high tension contractions, operates independently of receptors on the surface because it's already inside. Once inside the cell, IGF-1 interacts with calcium-activated enzymes and sets off a process that results in protein synthesis (and the calcium ions that were released during muscle contraction and also the ones that leak into the muscle after the sarcolemma is damaged ensure that the necessary enzymes are calcium-activated). A large part of this increase in protein synthesis rate is due to the fact that the IGF-1/calcium/enzyme complexes make protein synthesis at the ribosomes more efficient.
By the way, insulin works at the ribosome in a similar manner, hence the name insulin-like growth factor-1 (IGF-1). So get some quick digesting carbs in after your workout to raise insulin levels.
What about the GH?:
GH: GH is thought to work, primarily, by causing the cells (both liver and muscle cells) to release IGF-1. Effective training causes a rise in GH levels in the bloodstream; this GH prompts the liver to release paracrine IGF-1 several hours afterward, and also the muscle cells to release autocrine IGF-1, thus leading to another potential growth induction.
The IGF-1 presented in the liver could be the reason of the enhaced muscular grwing activity in any liver intake as the desicated pills.
When the sarcolemma (the muscle cell wall) is 'damaged' by tension (as in weight training or even stretching) growth factors are produced and released in the cell. There are several different types of growth factors. The most significant are:
Insulin-like Growth Factor 1 (IGF-1)
Fibroblast Growth Factor (FGF)
Transforming Growth Factor -Beta Superfamily (TGF-beta)
These growth factors can then leave the cell and go out into the surrounding area because sarcolemma permeabilty has been increased due to the 'damage' done during contraction. Once outside the muscle cell these growth factors cause the satellite cells to proliferate (mainly FGF does this) and differentiate (mainly IGF-1 does this). TGF-beta's role is one of mediation - in this case it inhibits growth. After this process the satellite cells then fuse with the muscle cells and donate their nuclei, giving the muscle cells the 'ability' to grow.
Now factors that promote protein synthesis such as IGF-1, growth hormone (GH), testosterone and some prostaglandins can commence the growth process. .....
IGF-1: IGF-1 comes in two varieties - paracrine IGF-1 is made primarily in the liver and autocrine IGF-1 is made locally in other cells. Paracrine IGF-1 travels through the bloodstream to the various tissues of the body, but autocrine IGF-1 is local in that in affects only tissues in the area in which it is released. Receptors on the surface of the cells are necessary for paracrine IGF-1 to enter the cells and exert its anabolic effects. But autocrine IGF-1, which is manufactured and released in the muscle cell as a response to high tension contractions, operates independently of receptors on the surface because it's already inside. Once inside the cell, IGF-1 interacts with calcium-activated enzymes and sets off a process that results in protein synthesis (and the calcium ions that were released during muscle contraction and also the ones that leak into the muscle after the sarcolemma is damaged ensure that the necessary enzymes are calcium-activated). A large part of this increase in protein synthesis rate is due to the fact that the IGF-1/calcium/enzyme complexes make protein synthesis at the ribosomes more efficient.
By the way, insulin works at the ribosome in a similar manner, hence the name insulin-like growth factor-1 (IGF-1). So get some quick digesting carbs in after your workout to raise insulin levels.
What about the GH?:
GH: GH is thought to work, primarily, by causing the cells (both liver and muscle cells) to release IGF-1. Effective training causes a rise in GH levels in the bloodstream; this GH prompts the liver to release paracrine IGF-1 several hours afterward, and also the muscle cells to release autocrine IGF-1, thus leading to another potential growth induction.
The IGF-1 presented in the liver could be the reason of the enhaced muscular grwing activity in any liver intake as the desicated pills.