Uptake of 125I-labelled toluidine blue and ) 775Se{-seleno- methionine in the parathyroids of rabbits. )]

Abstract125I-labelled toluidine blue was injected i.v. into rabbits, and the selective uptake in the parathyroids was compared with that of [75Se]-selenomethionine. The radioiodinated dye concentrated in the parathyroids 3.3 times more than in the thyroid, with a maximum uptake at 30 seconds (the shortest time interval studied). For [75Se]-selenomethionine the comparable figure was on an average, 3.7 and was reached after 20 minutes. The maximum uptake per g of 125I-labelled toluidine blue in the parathyroids was approximately 0.6% of the total amount injected, and of [75Se]-selenomethionine approximately 0.2%. Within 5 minutes the concentration of dye in the thyroid equalled that in the parathyroid, indicating that preoperative detection of parathyroid adenomas in humans is limited to gamma camera studies.Key Words: Parathyroidrabbit[75Se]-selenomethioninetoluidine blue