Measurement of non-specific binding by parallel or consecutive incubation procedures in receptor homogenates following tissue disintegrations by sonification.

It was demonstrated with 125I-labeled insulin and homogenates of human placenta that the energy and duration of tissue disintegration by sonification markedly affected the extent and reproducibility of binding. If the non-specific binding was determined by consecutive incubation on identical samples, as was the total binding, the data obtained were more reproducible and closer to the affinity values and number of receptors that had been obtained on isolated trophoblast membranes when compared to experiments in which the non-specific binding was measured on different samples than for the total binding. On isolated membranes, the results were almost unaffected by the method of measuring non-specific binding. Therefore, we suggest that total and non-specific binding should be measured consecutively on identical samples if only small amounts of homogenized tissue are available.