Hypotheses on physiological roles of prostaglandins.

Prostaglandin, a smooth muscle-stimulating depressor acidic lipid discovered int he human seminal plasma in 1935, is now used as a generic term for a family of closely related derivatives of prostanoic acid which are widely distributed in animal tissues. Prostaglandins are biosynthesized from arachidonic acid and dihomo-gamma-linolenic acid, both of which are derived from dietary linoleic acid. This finding provided a link to the observation that linoleic acid is an essential constituent of the diet. It is possible that prostaglandin compounds play a biochemical role fundamental to many, or all, animal cells. They have been implicated in sperm transport, menstruation, parturition, and control of placental blood flow. They may also play a role in the central nervous system, although this role may well be other than that of synaptic transmitter. Release of prostaglandin from various tissues is brought about by nerve stimulation. In adipose tissues, the amounts released may be sufficient to inhibit formation of cyclic AMP by the released noradrenaline, thus providing a local negative feedback mechanism. Prostaglandins also possibly play a role in muscular contractility, essential fatty acid deficiency, inhibition of lipid mobilization, atherosclerosis, and thrombosis.