Antidiuretic Action of a Corpus Cardiacum Factor (Ctsh) on Long-Term Fluid Absorption Across Locust Recta in vitro

Long-term fluid absorption (Jv) by everted rectal sacs from locusts is stimulated by both corpus cardiacum (CC) extracts and cAMP in a dosedependent manner. This hormonal antidiuretic activity (ADH) is present in both nervous and glandular lobes of CC. This distribution is similar to that of chloride transport stimulating hormone (CTSH) but not to that of other factors previously reported from this gland. As expected if ADH were due to CTSH acting on electrogenic Cl− transport, CC extracts also increased the electropotential across rectal sacs, and the stimulation of fluid absorption ceased in Cl-free salines. CC extracts also caused recta to absorb fluid against larger osmotic gradients, suggesting that the antidiuretic factor acts on the ion-dependent active transport of fluid rather than on the osmotic permeability of the rectal wall.