What type of effects do prostaglandins produce on smooth muscles? List two examples.

First, they may produce direct and relatively short-lived effects, such as stimulation of the isolated uterus or relaxation of the isolated tracheal chain preparation.

Secondly, in doses too low to produce a direct effect, they may produce a long-term potentiation of the effects of other stimulants.

it means there are 3 atoms of oxygen