Studies on locust rectum. III. Stimulation of electrogenic chloride transport by hemolymph

Abstract

Hemolymph was collected from recently fed desert locusts either by adsorption onto filter paper, or by centrifugation and methanol extraction. Whole hemolymph caused both the short-circuit current (I_sc) and open-circuit transepithelial electropotential difference (PD) across locust recta mounted in Ussing-type chambers to double during the steady-state period. Methanol extracts of hemolymph caused similar but smaller increases in I_sc. The transepithelial resistance (R) did not change. Simultaneous measurements of ³⁶Cl⁻ fluxes indicated that all of the increase in I_sc following stimulation could be accounted for by a parallel increase in net Cl⁻ absorption from the lumen side. With the exception of an initial small biphasic fluctuation in I_sc, stimulation by hemolymph exhibited identical characteristics to those produced by submaximal dosages of corpora cardiaca (CC). Cardiatectomy drastically reduced the stimulatory activity of hemolymph, suggesting that this neuroendocrine organ is the source of the active factor (chloride transport stimulating hormone (CTSH)) in hemolymph.