The human SLC5A3 gene encodes a Na+/myo-inositol (Ins) transporter also known as SMIT1 (Berry et al. 1995). The stoichiometry and inositol specificity of the human transport reaction are inferred from the properties of cloned canine protein expressed in Xenopus oocytes (Hager et al. 1995). SMIT1 functions in cellular osmoregulation and is expressed in many human tissues including skeletal muscle, brain, kidney, and placenta.