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CHARACTERISTICS OF PROSTAGLANDINS

1975; Elsevier BV; Volume: 15; Issue: 2 Linguagem: Inglês

10.1051/rnd

1297-9708

A. L. WALPOLE,

Analytical Methods in Pharmaceuticals

The natural prostaglandins (PGs) are all unsaturated hydroxy acids of 20 carbon atoms based on a 5 -membered ring with 2 adjacent side-chains.There are four main series, designated E, F, A and B, denoting differences in the ring.They occur widely in mammalian tissues but in very low concentrations except in the seminal fluid of certain species, including man.In human semen, the richest source, at least 15 PGs have now been identified, in a total concentration of ca.300 !g!ml.The PGs are formed in many tissues, often in response to stimulation, by biosyn- thesis from unsaturated fatty acids, e.g.arachidonic.After release into the circulation the PGFs are very rapidly metabolised, mainly in the lung and liver, to inactive urinary excretion products.PGAs are rather less rapidly inactivated.The PGs have a remarkably wide range of pharmacological activities, in respect of which they are often extremely potent.Members of the different series exhibit different specificities of action, and pharmacological responses are often species-dependent.PGEs usually lower blood pressure, stimulate gastro-intestinal and uterine smooth muscle and relax respiratory smooth muscle.PGFs have pressor effects in some species, and in some cause broncho-constriction.In other respects their effects on smooth muscle are broadly similar but less marked than those of the Es.Other responses to PGEs include inhibition of gastric secretion, diuresis and natriuresis, inhibition of platelet aggregation (E l ), inhibition of lipolysis and a variety of CNS effects.In many respects the PGAs resemble PGEs in their biological effects, but lack many of the potent actions of the latter on metabolism and on non-vascular smooth muscle.Both PGFs and PGEs affect reproductive function in a variety of ways, and PGF 2 .is notable for its capacity to induce luteolysis which has been demonstrated in all species studied except man and dog.Endogenous PGs have, probably, a physiological role in the regulation of function in, e.g. the cardiovascular renal, gastro-intestinal, nervous and reproductive system, and an aetiological role in hypertension, peptic ulcer, diarrhoea and bronchial asthma.The use of PGF2!, E l and E 2 for the induction of labour and abortion in women depends in the main on their oxytocic activity but other factors may be involved.The use of PGF2! for oestrous control in domestic animals depends on its luteolytic action.Analogues have been sought having increased luteolytic potency without a corresponding increase in tosixity.In a series of 1 6-ary- loxyprostaglandins compounds with these characteristics -notably ICI 8o, 99 6 and ICI 8z,oo8 - have been found.