Prostaglandins physiological effects

Essential Fatty Acids Do Not Exert All Their Physiologic Effects Via Prostaglandin Synthesis... 

PRIMARY PHYSIOLOGIC EFFECTS OF THE MAJOR CLASSES OF PROSTAGLANDINS, THROMBOXANES, AND LEUKOTRIENES ... 

Other Pathologies. Because of their many varied physiologic effects, the eicosanoids are involved in a number of other pathologic conditions. Prostaglandins have been implicated in cardiovascular disorders (hypertension), neoplasms (colon cancer), respiratory dysfunction (asthma), neurologic disorders (multiple... 

The primary endocrine glands and the hormones they produce are briefly discussed here. These glands and the physiologic effects of their hormones are also summarized in Tables 28-1 and 28-2. For the purpose of this chapter, only the primary endocrine glands and their respective hormones are discussed. Substances such as prostaglandins and kinins, which are produced locally by a variety of different cells, are not discussed here, but are referred to elsewhere in this text (e.g., see Chapter 15). Also, chemicals such as norepinephrine, which serve a dual purpose as hormones and neurotransmitters, are discussed in this chapter only with regard to their endocrine function. 

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]. 

The eicosanoids—prostaglandins (PGs), thromboxanes (TXs), prostacyclins (PGIs), and leukotrienes (LTs)—are derived from essential fatty acids and act similarly to hormones (Chapter 30). However, they are synthesized in almost all tissues (unlike hormones, which are synthesized in selected tissues) and are not stored to any significant extent their physiological effects on tissues occur near sites of synthesis rather than at a distance. They function as paracrine messengers and are sometimes referred to as autacoids. 

Fatty acids are saturated and unsaturated carboxylic acids containing between twelve and twenty-four carbon atoms. Fatty acids with even numbers of carbon atoms occur most frequently in nature. The reactions of fatty acids are identical to those of carboxylic acids. They include esterification, production by acid hydrolysis of esters, saponification, and addition at the double bond. Prostaglandins, thromboxanes, and leukotrienes are derivatives of twenty-carbon fatty acids that have a variety of physiological effects. 

Eicosanoids (like prostaglandin) exert specific physiological effects on target cells, like hormones. However, eicosanoids are distinct from most hormones in that they cat locally, near their sites of synthesis, and they are catabolized extremely rapidly. Thus, eicosanoids are considered to be locally acting hormones. 

Keuhl, F. A., and R. W. Egan. Prostaglandins, Arachidonic Acid, and Inflammation. Sdence2 Q, 978-984 (1980). [A discussion of the chemistry of these compounds and their physiological effects.]... 

Prostaglandins in blood platelets can inhibit their aggregation. This is one of the important physiological effects of prostaglandins. 

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