Mechanism of technetium 99m sestamibi parathyroid imaging and the possible role of p-glycoprotein.
BACKGROUND
Localization of parathyroid glands is critical in the treatment of recurrent or persistent hyperparathyroidism. Technetium sestamibi imaging may improve localization; however, the mechanism of visualization of parathyroid tissue remains unclear. On the basis of the chemical structure of sestamibi it has been suggested that p-glycoprotein is involved in the transport of sestamibi across cell membranes. This study was designed to examine sestamibi uptake and retention and p-glycoprotein expression in normal and abnormal parathyroid tissue.


METHODS
Thirty-two consecutive patients underwent 2-methoxy-isobutyl-isonitrile imaging immediately before parathyroid exploration. Tissue was obtained from normal and abnormal parathyroids and from the thyroid gland. Touch preparations gave rapid confirmation of tissue origin. Specimens were trimmed and weighed, and gamma-emission was counted. Percentage injected dose per gram of tissue was calculated. Immunohistochemistry was obtained with a battery of monoclonal antibodies to identify p-glycoprotein in parathyroid tissue submitted for permanent histologic examination. Slides were graded by a pathologist familiar with immunohistochemistry.


RESULTS
Abnormal parathyroid tissue had a higher mean retention of injected dose per gram than did normal thyroid and parathyroid tissue. Immunohistochemistry revealed that abnormal parathyroid tissue expresses less p-glycoprotein.


CONCLUSIONS
These results suggest that size is not the single determinant of parathyroid visualization and that p-glycoprotein expression may be involved in the mechanism of parathyroid imaging.
Mitchell
B K
BK
Division of Endocrine Surgery, West Haven Veterans Affairs Medical Center, Conn, USA.
Cornelius
E A
EA
Zoghbi
S
S
Murren
J R
JR
Ghoussoub
R
R
Flynn
S D
SD
Kinder
B K
BK
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism / Q000502:physiology*; D000236:Adenoma / Q000378:metabolism; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D006961:Hyperparathyroidism / Q000000981:diagnostic imaging / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D010280:Parathyroid Glands / Q000000981:diagnostic imaging* / Q000378:metabolism*; D010282:Parathyroid Neoplasms / Q000378:metabolism; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D012016:Reference Values; D017256:Technetium Tc 99m Sestamibi; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi