Hemocytes of Pomacea canaliculata: I. Reversible aggregation induced by Ca2+

Using a platelet aggregometer, factors involved in hemocyte aggregation of a prosobranch snail Pomacea canaliculata were investigated. Aggregation-inducing tests revealed that extracellular Ca2+ is required to provoke the cellular response which is reversible. The aggregation-dispersion response can be induced by adding Ca2+ and EDTA alternately. Aggregation was inhibited by a calmodulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) in a dose-dependent manner, and by a protein kinase-C inhibitor 1-(5-isoquinolinesulfonyl)-2-methyl-piperazine dihydrochloride (H-7). Thus, calmodulin and protein kinase-C may contribute to the calcium-mediated aggregation of hemocytes, which resembles a phenomenon that occurs in vertebrate leucocytes. Unlike the aggregation of mammalian leucocytes, no stimulus other than Ca2+ is required to induce the response of Pomacea hemocytes. Thus, this system may serve as a simple model for analysing cellular aggregation responses.