Objective To study the difference between the mRNA expressions of hyaluronan synthase in the epithelial cells of endolymphatic sac and renal tubules with the oligonucleotide probe. Methods The oligonucleotide probe of hyaluronan synthase was designed and synthesized, the mRNA expressions of hyaluronan synthase in the epithelial cells of endolymphatic sac and renal tubules were detected with hybridization in situ. Results mRNA of hyaluronan synthases were strongly expressed in some epithelial cells of endolymphatic sac and renal tubules. Conclusion It is confirmed that a dual regulatory system for hyaluronan /hyaluronidase exists in the epithelial cells of endolymphatic sac and renal tubules at the level of molecular biology.