The mechanism of hormone action
The 1971 Nobel Prize in Physiology or Medicine was awarded to Earl W. Sutherland Jr. for his work on the action of hormones. Inspired by Carl Cori and his work on the pathways of glycogen breakdown and glucose synthesis in mammalian liver cells, Sutherland focussed his work on how the hormone epinephrine regulates glycogen synthesis.
Epinephrine is a hormone produced by the adrenal gland and is transported in the blood stream to different organs in the body. It is released during stress to prepare the individual to new situations and defence. It permits, at a cellular level, the liberation of glucose for the production of energy.
Sutherland focussed on the liver and muscle cells. He discovered a new chemical that acts as an intermediate in hormone signalling: cyclic AMP. Simply put, the hormone is sent out in the blood stream and attaches to receptor on cell membranes. These activated receptors then turn on a chemical cascade in the cell resulting in changes in gene expression and in cell response, thanks to this 2nd messenger. The hormone never enters or diffuses within the cells - its information is translated in the cell through the activity of cAMP that transports the hormone signal to the cell machinery.
Later on, in the 1960s, cAMP was found to not only be associated to epinephrine activity but also with many other hormones. Sutherland had put his finger on a new biological principal, a general mechanism for the action of hormones.
In 1965, cAMP was also found in bacteria which have apparently no use for hormones., It turns out that cAMP has important regulatory functions which aid the bacterial cells in their adaptation to the environment..
Sutherland had proven that hormones work at a cellular and molecular level so that higher organisms can function as a unity and bacteria and other procaryotes can respond to their environment, . cAMP turned out to be one of the fundamental principals involved in the regulation of essentially all life processes.