Structure-activity relationships of two Rhodnius prolixus calcitonin-like diuretic hormone analogs.

The calcitonin-like diuretic hormone (CT/DH) in Rhodnius prolixus influences various tissues associated with feeding-related physiological events. The receptors for this peptide have also been identified and shown to be expressed in these tissues. In the present study, we have investigated the effects of two R. prolixus CT/DH analogs (full-length form and N-terminal truncated form) on hindgut contractions and in a heterologous receptor expression system. The analogs contained the amino acid methyl-homoserine in place of methionine in order to prevent them from being oxidized and thus increase their stability. The full-length form of the analog retained all of its activity in our assays when compared to the endogenous peptide. Truncated analog displayed no activity in our assays.