SALT AND WATER TRANSPORT BY IN VITRO COCKROACH MIDGUT

The utilization of in vitro midgut preparations has shown that hyperosmotic lumen concentrations fail to elicit the movement of water from the haemolymph across the epithelium. On the other hand, the osmolarity of the midgut lumen decreases which indicates a rapid absorption of solutes. These results suggest that the ventriculus plays an important rôle in maintaining overall homeostasis while allowing the required absorption. Varied placement of 0·001 M dinitrophenol (DNP) and varied lumen salt concentration indicate that there are two DNP sensitive movements across the gut wall in opposite directions. Saturation kinetics of inhibition can be shown when DNP is placed on the blood-side of the midgut. The significance of DNP-inhibited transport and of other absorptive mechanisms are discussed. © 1969.