Sulphate conjugation of isoprenaline by lung, small intestine and other organs.

Isoprenaline, a sympathomimetic drug used in the treatment of asthma, was found to be sulphated by the bronchial tissues of the monkey and dog. Enzyme preparations of the liver, small intestine and kidney of various animals are also able to catalyze this sulphate conjugation reaction from ATP and inorganic sulphate and from a commercial preparation of adenosine 3'-phosphate 5'-sulphatophosphate (PAP35S) or PAP35S generated from Na235SO4 in vitro. The Km values for isoprenaline for the sulphotransferase of mouse liver and monkey lung, are respectively, 51,3 microM and 138 microM . The significance of this detoxication reaction is discussed in relation to (a) the importance of lung as a potential biotransformation site of isoprenaline, (b) asthma deaths supposed to be associated with the use of isoprenaline in the form of pressurised aerosols and (c) the ability of the different tissues to synthesize PAPS in vitro.