Prostaglandin relaxation/contraction

Physiological responses to prostaglandins encompass a variety of effects Some prostaglandins relax bronchial muscle others contract it Some stimulate uterine con tractions and have been used to induce therapeutic abortions PGEj dilates blood vessels and lowers blood pressure it inhibits the aggregation of platelets and offers promise as a drug to reduce the formation of blood clots... 

Gastrointestinal smooth muscles Prostaglandin E2 contracts longitudinal but relaxes circular smooth muscles, whereas prostaglandin F2 contracts both. 

The multiple drug effects on smooth muscles are also little understood. Thus, isoprenaline relaxes and adrenaline and noradrenaline contract the isolated rat aorta, but all three catecholamines increase cyclic AMP formation [61]. Adrenaline induces relaxation and prostaglandin Ei contraction in the estrogen-treated rat isolated myometrium, but both adrenaline and prostaglandin Ei elevate the cyclic AMP level in the tissue [62]. An example of a critical evaluation of the evidence linking cyclic AMP to a physiological effect (cardiac contractility) is that of Sobel and Mayer [63]. 

Although prostaglandins are broken down quickly, they have potent physiological effects. Some prostaglandins increase blood pressure, and others lower blood pressure. Other prostaglandins stimulate contraction and relaxation in the smooth muscle of the uterus. When tissues are injured, arachidonic acid is converted to prostaglandins that produce inflammation and pain in the area. 

The most important known effects of the prostaglandins and other eicosanoids are the contraction and relaxation of smooth muscles ... 

Prostaglandins Lower blood pressure Inhibit blood platelet aggregation Control inflammation Lower gastric secretions Stimulate uterine contractions Relax smooth muscles of the uterus... 

The various prostaglandins and their receptors represent a bewildering array of functions. However, these have been corvenieirtly divided into three functions (1) relaxation (2) contraction and (3) inhibition. The relaxation receptors are those that bind PGl, PCD, PCEj, and PGE. The stimulation of these receptors results in an increase in cvtosolic cAMP. and muscle relaxation. 

Certain prostaglandins have opposite effects in different organs, that is, their receptors are tissue-specific. (For example, several E-series prostaglandins cause smooth muscle relaxation in organs such as the intestine and uterus. The same molecules promote contraction of the smooth muscle in the cardiovascular system.)... 

The prostaglandin era began with its biodetection by Kurzrok (12) in 1930 in human semen, which was shown to contract or relax strips of human uterus. For the next 29 years prostaglandin research moved at a slow pace, averaging one publication per year, while steroid hormone... 

Prostaglandins also act on gastrointestinal circular muscle. However, whereas PGFs produce contraction as in the case of the longitudinal smooth muscle, with PGEs the effect is that of relaxation [216-218]. 

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