Fig. 7. Antagonism between Tenebrio molitor peptides controlling Malpighian tubule secretion and between their second messengers. Effect of adding Tenmo-ADF (ADF) to tubules already stimulated with Tenmo-DH₃₇ (DH37) (both at concentrations of 100 nmol l^–1) compared with the effect of adding cyclic GMP to tubules already stimulated with cyclic AMP (both at concentrations of 0.5 mmol l^–1). Secretion rates were measured after 45 min of each treatment. Values are means + 1 S.E.M. for eight tubules (peptides) or seven tubules (second messengers). C, control rates.