Somatostatin and calcitonin modulate gastropod internal defense mechanisms

Immunoreactive somatostatin and calcitonin are stored in selected mammalian leukocytes. Synthetic somatostatin and calcitonin can alter the functional activity of certain mammalian blood cells. These findings suggest that the two enteroneuro-peptides serve as modulators of the mammalian immune system. The aim of the present study is to determine whether the 2 peptides are also found in gastropod blood cells and whether they may participate in the regulation of the gastropod internal defense mechanisms. We found that somatostatin-like and calcitonin-like substances are located in a distinct population of hemocytes from the pond snail Physella heterostropha and that the amount of immunoreactive calcitonin in hemocytes increases after an injury to the body wall. Synthetic somatostatin and calcitonin stimulate the attachment of latex beads to in vitro cultured hemocytes. We conclude that the somatostatin- and calcitonin-like substances may serve as modulators of the internal defense system of gastropods.