CGRP-like molecules and carbonic anhydrase activity during the growth of Pecten maximus

In order to investigate the physiological role of calcitonin gene-related peptide (CGRP) in mollusc, both circulating CGRP-related molecules and gill or mantle carbonic anhydrase activity were analysed during the annual growth of Pecten maximus. CGRP like molecules measured by radioreceptor assay increased significantly during the annual cycle. Similarly, gill carbonic anhydrase activity increased and showed a maximum activity when growth is stimulated to the greatest extent. Correlation studies showed a significant relationship between the tissue weight and either the gill carbonic anhydrase activity or the CGRP-related molecules determined by radioreceptorassay. This observation suggests a possible interaction between carbonic anhydrase activity and CGRP. Accordingly, we searched for a direct effect of CGRP on the gill carbonic anhydrase activity. In gill membranes, CGRP stimulated the carbonic anhydrase activity. The maximum effect was obtained at a CGRP concentration of 50 nM.