A rapid filtration method for receptor binding: characterization with mu and delta opiate receptors

A commercially available (Skatron) cell harvester was adapted for use in mu (3H-naloxone-labeled) and delta (3H-DADLE-labeled) opiate receptor assays and compared with a widely used conventional manifold for a number of binding characteristics. Whatman GF/B glass fiber filters and the less expensive filters available with the harvester were also compared and produced similar binding characteristics on the harvester and manifold if the harvester filters were used double-ply, and if the rinse time was less than 12.5 sec. Longer rinse times produced lower binding with 2-ply Skatron filters. Kd values, Hill coefficients, and Scatchard plot regression coefficients were very similar for the two filtration devices and filter types. A significantly reduced maximum number of sites (Bmax) was observed after filtration on the harvester, reflecting the smaller filter surface area relative to that of the manifold. The filter surface area on the harvester, nevertheless, is considerably larger than that of other manifolds with microplate spacing. This provides the advantages of rapid filtration with less restriction on tissue concentrations. Specific binding was linear with protein concentration up to at least 800 micrograms protein, which is well within the range of most neurotransmitter and peptide receptor binding studies. At about 1 mg protein the rinse buffer flow was slower due to the high tissue concentration. Although the results of filtration with the harvester and the conventional manifold were similar, the time requirements differed considerably. With the harvester, one experimenter could conduct the filtration process 2-3 times faster than 2 experimenters using the manifold.(ABSTRACT TRUNCATED AT 250 WORDS)