In vivo quantification of human pulmonary beta-adrenoceptor density using PET: comparison with in vitro radioligand binding.
A new method has recently been developed to quantify pulmonary beta-adrenergic receptors in vivo using PET. This study used in vitro radioligand binding assay (RLBA) as the gold standard to validate in vivo PET measurements.


METHODS
Five male patients with lung cancer aged 57 yr (range 42-67 yr) were studied. PET scanning was performed the day before thoracotomy to determine regional pulmonary beta-receptor density. RLBA was carried out on cell membranes prepared from specimens of lung tissue obtained at the thoracotomy to measure beta-receptor density in vitro. In both cases, the hydrophilic nonselective beta-antagonist radioligand (S)-CGP-12177 was used. For PET studies, this was labeled with 11C and for RLBA with 3H.


RESULTS
In the PET study, beta-receptor density (Bmax) was 9.43 +/- 1.32 pmole g-1 tissue. In the RLBA study, Bmax was 99.0 +/- 15.5 fmole mg-1 protein, equivalent to 9.90 +/- 1.55 pmole mg-1 tissue. These values are in good agreement with previously reported in vitro measurements on human lung membranes using 125I-iodocyanopindolol. A correlation was found between beta-adrenergic density obtained using PET and beta-adrenergic density obtained using RLBA (r = 0.92; p < 0.05).


CONCLUSIONS
The results support the use of PET as a new method for imaging and the way for studies of physiological and pharmacological regulation of beta-adrenergic receptors through noninvasive serial measurements.
Qing
F
F
MRC Clinical Sciences Center, Royal Postgraduate Medical School, Hammersmith Hospital, London, United Kingdom.
Rhodes
C G
CG
Hayes
M J
MJ
Krausz
T
T
Fountain
S W
SW
Jones
T
T
Hughes
J M
JM
D000319:Adrenergic beta-Antagonists; D002250:Carbon Radioisotopes; D002283:Carcinoma, Bronchogenic / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D008168:Lung / Q000000981:diagnostic imaging*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011412:Propanolamines; D011869:Radioligand Assay; D011943:Receptors, Adrenergic, beta / Q000032:analysis*; D014055:Tomography, Emission-Computed; D014316:Tritium
D000319:Adrenergic beta-Antagonists; D002250:Carbon Radioisotopes; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; D014316:Tritium; C033394:CGP 12177