Effect of corpus cardiacum, ventral ganglia, and proline on absorbate composition and fluid transport by locust hindgut

Abstract

Extracts of corpus cardiacum and fifth ventral ganglion stimulated transport of K+, Cl−, and fluid across everted rectal sacs exposed luminally to either high-NaCl or high-KCl saline, whereas there was little or no increase in Na+ absorption. These results contrast with the large increase in Na+ absorption across the ileum caused by the same extracts. Moreover, proline transport across the two hindgut segments differs: a large net proline flux occurs across the rectum but not the ileum under similar conditions. Not surprisingly, therefore, increasing proline concentrations in the bathing saline had no effect on ileal fluid transport. However, changing the external proline concentration from 1 to 80 mM caused a substantial increase in fluid transport across everted rectal sacs, and this persisted when external Na+, K+, and Cl− were absent, and when the osmolarity of the luminal saline was increased.