The Effect of Platelet Protein and Dna on the Measurement of Human Lymphocyte Beta Adrenergic Receptor Number

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.