Abstract
Considerable variation exists in human lymphocyte beta adrenergic receptor measurements when the data are reported as fmole/mg protein. To investigate potential sources of measurement errors, human lymphocytes were prepared as follows: With the standard method (M1), lymphocytes were removed from heparinized whole blood by centrifugation on a ficoll gradient. The modified method (M2) was identical, except for an initial centrifugation to remove platelet-rich plasma. Beta adrenergic receptors were measured by the binding of [125I] pindolol with the results analyzed by the method of Scatchard. The M1 receptor number was 11.9±1.8 fmole/mg protein compared to 26.7±4.1 fmole/mg for M2 (p1/40.01). Since platelet-rich M1 had 71.9 ug protein/100 uL of sample and platelet-poor M2 had 23.8 ug/100 uL the difference in receptor number is a calculation artifact due to platelet protein. Similar results were obtained when data were expressed as fmole/mg DNA, because platelets also contain nucleic acids. However, when expressed as the number of binding sites/cell, neither platelet protein nor platelet-DNA affected receptor quantitation. We conclude that results are most accurately reported as sites/cell.