Turnover of sulphur compounds in the endolymphatic sac: an autoradiographic study in the Mongolian gerbil.

Complex macromolecules are suggested to play an important role for the function of the endolymphatic sac (ES). As proposed in previous experimental studies, proteoglycans are supposed to be present in the ES. As they are composed of a proteic core linked to chains of glycosaminoglycans, chemical identification of the glycosaminoglycans is of particular importance, bearing in mind that all but hyaluronic acid contain sulphur. In order to follow the short-term turnover of sulphur in the ES, an autoradiographic study has been carried out in the Mongolian gerbil using 35S as tracer. Radioactive labelling of the gerbilline ES was controlled 15, 20, 30 and 60 min after intraperitoneal injection. While the first signs of the presence of radioactive sulphur were noticed after 20 min in the blood vessels and in the basal aspect of the ES epithelium, after 60 min it was possible to observe the presence of the tracer both within the epithelial cell layer as well as in the lumen of the ES. These findings are consistent with the presence of a fast turnover of sulphur molecules in the gerbilline ES.