Farmasevtika instituti farmakologiya va klinik farmatsiya kafedrasi

Enhancement of Amino Acid Transport Through the Cell Membranes. 
Growth 
hormone directly enhances transport of most amino acids through the cell membranes to the interior of 
the cells. This increases the amino acid concentrations in the cells and is presumed to be at least partly 
responsible for the increased protein synthesis 
Increased Nuclear Transcription of DNA to Form RNA. 
Over more prolonged periods (24 
to 48 hours), growth hormone also stimulates the transcription of DNA in the nucleus, causing the 

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formation of increased quantities of RNA. This promotes more protein synthesis and promotes growth 
if sufficient energy, amino acids, vitamins, and other requisites for growth are available. In the long 
run, this may be the most important function of growth hormone. 
Decreased Catabolism of Protein and Amino Acids. 
In addition to the increase in protein 
synthesis, there is a decrease in the breakdown of cell protein. A probable reason for this is that growth 
hormone also mobilizes largequantities of free fatty acids from the adipose tissue, and these are used to 
supply most of the energy for the body‘s cells, thus acting as a potent ―protein sparer.‖ 
Summary. 
Growth hormone enhances almost all facets of amino acid uptake and protein 
synthesis by cells, while at the same time reducing the breakdown of proteins. 
Excitation and Contraction of Smooth Muscle 
Contraction of Smooth Muscle 
In Chapters 6 and 7, the discussion was concerned with 
skeletal muscle. We now turn to smooth muscle, which is composed of far smaller fibers—usually 1 to 
5 micrometers in diameter and only 20 to 500 micrometers in length. In contrast, skeletal muscle fibers 
are as much as 30 times greater in diameter and hundreds of times as long