Prolactin response to TRH in vitiligo

A more sensitive assay procedure has been developed for the enzyme iduronate 2-sulphate sulphatase which is deficient in the Hunter syndrome. The substrate is the same as previously described by Lim et al. 1], O-(α-l-idopyranosyluronic acid 2-sulphate)-(1 → 4)-2,5 anhydro-d-³H-1]mannitol 6-sulphate, but, after incubation, it is separated from the product by ion-exchange chromatography on a micro-column of Dowex 1 × 2 (Cl^?) instead of high voltage electrophoresis or ECTEOLA cellulose chromatography.Since the blank correction is then much smaller, a shorter incubation time can be used and conversion of the substrate reduced from approximately 50% down to levels where complications resulting from substrate depletion and product inhibition are minimal. Using whole serum the apparent K_m for the substrate is 0.2 mmol/1.With an incubation time of 20 min, sera from heterozygotes exhibited approximately 35% of the normal levels of iduronate 2-sulphate sulphatase (0.11–0.61, mean 0.34 nmol.h^?1.mg^?1 protein for 21 carriers; 0.24–2.35, mean 0.94 nmol.h^?1.mg^?1 protein for 37 normal females).Serum analyses can thus be used to supplement those on hair roots in the detection of carriers of the Hunter syndrome.