Sulphation of the heterocyclic amine 1,2,3,4-tetrahydroisoquinoline in the human liver and intestinal mucosa: Interindividual variability

The sulphation rate of 1,2,3,4-tetrahydroisoquinoline (TIQ) was measured in the human liver and in the intestinal mucosa isolated from the transverse colon, ileum and duodenum. The rate (mean +/- SD) of hepatic TIQ sulphation was 500 +/- 174 pmol/min per mg in women (n = 61) and 591 +/- 201 in men (n = 39; P = 0.0087), varying over one order of magnitude in men and women. The sulphation rate of testosterone showed the same sex-dependent pattern and was correlated (r = 0.6055; P < 0.001) with that of TIQ. The frequency distribution of TIQ sulphation rate in human liver was bimodal: 70% of the population fell into the low-activity subgroup and the remaining 30% feel into the high-activity subgroup. In the colon (n = 56), the rate of TIQ sulphation was 30.4 +/- 15.6 pmol/min per mg and the values were similar in men and women (29.8 and 30.9 pmol/min per mg, respectively) but, varied over one order of magnitude and correlated (r = 0.7231; P < 0.001) with that of 4-nitrophenol. The rate of TIQ sulphation changed along the human bowel and mean (+/- SD) estimates for duodenum, ileum and transverse colon were 444 +/- 25, 182 +/- 87 and 30.4 +/- 15.6 pmol/min per mg, respectively. The present results are consistent with the view that the heterocyclic amine TIQ is sulphated in the human liver and intestinal mucosa. TIQ-sulphotransferase activity varies among subjects and is mostly associated with the liver and duodenum.