Denominators in Hormone Action Receptors and Second Messengers

Common Denominators in Hormone Action Receptors and Second Messengers 

The preceding paragraphs introduced a number of circulating chemicals of various compositions, including 

The glucagon receptor is a glycoprotein, but in contrast to what is observed with insulin, treatment with phospholipase inhibits hormone receptors binding rather than activating it. 

Epinephrine and norepinephrine receptors have been detected on the membrane of the target cells. They are much more numerous than insulin receptors and less specific in that stereoisomers show similar binding properties, but elicit different physiological responses. 

Acetylcholine receptors are found on the muscle plates and have been isolated from cells of electric organs. They are certainly lipoproteins and possibly glycolipoproteins. Their concentration on the surface of the target organ is much greater than that for insulin. These differences in concentration of receptor sites are believed to have physiological meaning. 

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