Uptake of ¹²⁵I-Labelled Toluidine Blue and [⁷⁵Se]-Selenomethionine in the Parathyroids of Rabbits

Abstract

¹²⁵I-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:

• Parathyroid
• rabbit
• [⁷⁵Se]-selenomethionine
• toluidine blue