Intercellular messengers

Nitric Oxide. Nitric oxide [10102-43-9] NO, is a ubiquitous intracellular and intercellular messenger serving a variety of functions including vasodilation, cytotoxicity, neurotransmission, and neuromodulation (9). NO is a paramagnetic diatomic molecule that readily diffuses through aqueous and hpid compartments. Its locus of action is dictated by its chemical reactivity and the local environment. NO represents the first identified member of a series of gaseous second messengers that also includes CO. 

Myo-inositol is one of the most biologically active forms of inositol. It exists in several isomeric forms, the most common being the constituent of phospholipids in biological cell membranes. It also occurs as free inositol and as inositol hexaphosphate (IP6) also known as phytate which is a major source from food. Rice bran is one of the richest sources of IP6 as well as free inositol. Inositol is considered to belong to the B-complex vitamins. It is released in the gastrointestinal tract of humans and animals by the dephosphorylation of IP6 (phytate) by the intestinal enzyme phytase. Phytase also releases intermediate products as inositol triphosphate and inositol pentaphosphate. Inositol triphosphate in cellular membrane functions as an important intra- and intercellular messenger, that merits its value as a nutritional therapy for cancer. 

Garthwaite J., Charles, S. L., Chess-Williams, R., Endothelium-derived relaxing factor release on activation of NMDA receptors suggests role as intercellular messenger in the brain, Nature 336 (1988), p. 385-388... 

Hormones are intercellular messengers. They are typically (1) steroids (e.g., estrogens, androgens, and mineral corticoids, which control the level of water and salts excreted by the kidney), (2) polypeptides (e.g., insulin and endorphins), and (3) amino acid derivatives (e.g., epinephrine, or adrenaline, and norepinephrine, or noradrenaline). Hormones maintain homeostasis—the balance of biological activities in the body for example, insulin controls the blood glucose level, epinephrine and norepinephrine mediate the response to the external environment, and growth hormone promotes normal healthy growth and development. 

Hormones are intercellular messengers insulin is used to treat diabetes, while growth hormone promotes bone and tissue growth. 

Hormones are molecules that act as intercellular messengers. These are produced by endocrine glands in the body and are poured directly in the blood stream which transports them to the site of action. 

NO fulfills many criteria required to qualify as an intracellular and intercellular messenger. NO is formed with the help of specific enzyme systems activated by extracellular and intracellular signals. NO is synthesized intraceUularly and reaches its effector molecules, which may be localized in the same cell or in neighboring cells, by diffusion. Thus, it has the character of an autocrine or paracrine hormone, as well as an intracellular messenger. 

Shulman, E. M., and Madison, D. V. (1991). A requirement for the intercellular messenger nitric oxide in long-term potentiation. Science 254, 1503-1506. 

The interactions between immune and inflammatory cells are mediated in large part by certain proteins, called lym-phokines, or interleukins (IL), that are able to promote cell growth, differentiation, and functional activation. Interleukins resemble hormones, which also function as intercellular messengers. In contrast to hormones, however, they are secreted by isolated cells rather than discrete glands. Several interleukins have been described each has unique biological activities as well as some that overlap with the oth-... 

Prostaglandins (PG s) are naturally occurring intercellular messengers. In fact, many of the actions of anabolic substances fail to exert their protein synthesis actions without them. It is a clinical fact that there is a parallel between the rise of some levels of PG s and the degradation of catabolism. So they may in part be the relay between receptor-sites and translation to specific responses, or secondary messengers. 

Fig. 3.1 Pri ncipal mechanisms of intercellular communication, a) communication via intercellular messengers, b) communication via gap junctions. Gap junctions are direct connections between cells. They are coated by proteins (drawn as circles in the figure above) that can have a regulatory influence on the transport, c) communtication...

Buckley, N.J., 1990. Molecular pharmacology of cloned muscarinic receptors. In Nahorski. S.R., (Ed.), Transmembrane Signaling, Intercellular Messengers and Implications for Drug Development. Wiley, pp. 11-31. 

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