Calcitonin gene-related peptide receptors in pig spleen and the involvement of the CGRP(1) receptor in the splenocyte function

Calcitonin gene-related peptide (CGRP)-positive nerve fibers have been foun d in the trabecula and parenchyme area of pig spleen. Receptor studies have demonstrated that the CGRP binding site in pig spleen membranes has an ave rage K-d 2.24 +/- 0.48 nM and B-max 78 +/- 4.09 fmol/mg of protein. In the K-d range demonstrated in the binding studies, the dose-dependent suppressi ve effect of CGRP on spleen T lymphocyte proliferation was found with the m aximal effect in 10(-9) M concentration. The same effect, but in a differen t concentration, was found on peripheral blood T lymphocytes with the maxim um in 10(-6) M concentration. Contrary to the results obtained through the simultaneous presence of CGRP and mitogen, preincubation with CGRP led to a stimulation of peripheral blood lymphocytes in response to ConA and had no effect on spleen T lymphocytes. These results illustrate the difference in CGRP effect between lymphocytes of different origins. Using CGRP, receptor antagonist CGRP(8-37), we established that the CGRP suppressive effect on spleen T lymphocyte proliferation is CGRP(1)-receptor mediated.