B complex vitamins activate rat guanylate cyclase and increase cyclic GMP levels.

Since B complex vitamins and the intracellular messenger cyclic guanosine monophosphate (GMP) have similar effects of promoting growth, DNA and protein synthesis, the present investigation was designed to determine if the B complex vitamins' mechanism of action might involve cyclic GMP. All of the B complex vitamins increased rat cyclic GMP tissue levels. The cause of these increased cyclic GMP levels was activation of the enzyme guanylate cyclase [E.C.4.6.1.2.] which was increased significantly (P less than 0.001) in a variety of tissues at the l nmol l-1 concentration of these vitamins. The maximal activation of this enzyme required the presence of manganese ion. The present investigation suggests that the guanylate cyclase-cyclic GMP system may play a role in the mechanism of action of B complex vitamins at the cellular level.