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Explanation of muscle cell permeability

guss

guss

MuscleHead
Aug 11, 2010
380
189
ANDROGEN ENTRY INTO THE MUSCLE CELL
As bodybuilders,one of our goals is to organize the meeting of testosterone/androgens to its receptors;However,as the androgen receptors are located INSIDE the muscle fibers,forcing the entry of testosterone/androgens into the cell can be problematic from time to time.The muscle cells are covered by a membrane made of fat that has several purposes.The first,of course,is to hold the cell together.Another obvious purpose is to prevent the entry of unwanted molecules.Normally,testosterone/androgens are not on the unwanted list,but if their concentrations inside your muscles become excessive,the cell will start to resist them.Muscle cells have several means of getting rid of a specific molecule.They can destroy it accelerate its exit or prevent its entry.

MEMBRANE RECEPTORS VS. NUCLEAR RECEPTORS
Hormone receptors can either be found on the surface of the cell(membrane receptors)or inside the cell(nuclear receptors).Insulin,GH and IGF-1 receptors are said to be membrane receptors,which means they don't have to enter the muscle cell to produce their anti-catabolic effects.Instead they act by "touching" the outer surface of the cell.Steroids such as testosterone fall into the second category.They have to enter the cell to gain access to its receptors.For years,scientists have assumed that the above classification is correct.We now know it is not.Insulin must enter the cell to produce its anti-catabolic actions.GH also produces effects once it's inside the cells.On the other hand,androgens can elicit some of their actions by binding to membrane receptors.In fact,the very first effect you feel when using certain androgens is mediated by a nongenomic(independent of the gene/chromosome)action on your nerves.In other words,some androgen receptors are located on the surface of your neurons.Certain androgens will,at least indirectly,act on those membrane receptors,which translates over to an increase in muscle strength.Unfortunately,the membrane androgen receptors have nothing to do with the receptors that initiate muscle GROWTH.

GETTING TESTOSTERONE/ANDROGEN RECEPTORS INTO THE CELL
You'd think that a small membrane made of fat wouldn't be that hard for a molecule to cross.Steroids are derived from cholesterol,which is a form of fat.The popular theory states that as androgens are sythesized from fat,they easily cross the lipid bilayer that constitutes the plasma membrane;I don't think that's entirely true.First,the inside of the muscle membrane contains small channels that act as "androgen pumps".That means the cell can pump in extra-cellular androgen molecules whenever your muscles need more androgens.It also implies that in case of androgen excess inside the cell,the pump is inactivated in order to slow the entry of new androgen molecules.A similar problem occurs in the realm of fat burning.The fat molecules that are released from adipose tissue aren't free to enter the muscle cells to be burned.That's one of the reasons it's so difficult to burn fat when you're on a diet.The fat molecules need a pump called "fatty-acid-binding-protein(FABP)to enter the cells.A lack of FABP severely reduces the rate of entry of fat molecules into the cell.

INCREASING CELL MEMBRANE FLUIDITY(PERMEABILITY)
If the androgen pumps are inactive,steroids can still enter the cell thanks to passive diffusion.Unfortunately,that kind of transport is slow.In case of androgen excess inside the muscle cells,the hormone's exit will be accelerated.If the entry of new testosterone/androgen molecules is slowed while their export is accelerated,the cell level of androgens will fall rapidly,which is certainly not what any of us want.Scientists haven't studied the regulation of the androgen pumps to any great extent,so we know very little about them.That makes it hard for us to play with them,so we're left with finding a way to accelerate the passive diffusion of the androgen molecules.Their rate of entry is determined in part by the fluidity of the muscle membrane,something we do know how to influence.The membrane lipid bilayer is composed of the fat you eat or that your body synthesizes.BY CHOOSING THE RIGHT DIETARY FATS,YOU CAN ENHANCE MEMBRANE FLUIDITY.It's easy to figure out which fats are the most fluid.Just put them in the refridgerator.Saturated fats,such as butter,cheese and other animal proteins,are solid at low temperatures.Polyunsaturated fats remain fluid even at low temperatures.Bodybuilders are looking for two types of polyunsaturated fats,omega-6 fats,such as that found in primrose oil,and omega-3 fats,such as that found in fish oil(flax-seed oil is also rich in this department as well),with the latter being even more fluid than the former.Of course,you want to minimize your intake of the solidifying fats to the bare minimum;That is,you want to avoid saturated fats.By increasing the content of omega-6 and omega-3 fats inside the muscle cell membrane,YOU MAKE IT POSSIBLE FOR MORE TESTOSTERONE/ANDROGENS TO ENTER THE FIBERS.You may already be familiar with the similar favorable properties the two polyunsaturated fats have on insulin actions because they increase membrane fluidity.THEIR INFLUENCE ON CELL PERMEABILITY IS NOT TO BE NEGLECTED....
 
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