Sodium and chloride transport in the isolated intestine of the earthworm, Lumbricus terrestris (L.).

1. Measurements of electrical potential difference (PD), short-circuit current (SCC) and unidirectional fluxes of sodium and chloride were made across portions of the intestine. Based on the results, the intestine can be divided into at least four physiologically distinct regions. 2. These four physiological regions, designated from anterior to posterior as R I-II, R III A, R III B and R IV, do not completely correspond to the four anatomically distinct regions of the intestine. 3. The PD (serosal side positive) in R I-II, R III A, R III B and R IV is 1.08, 12.4, 5.61 and 31.7 mV, respectively. 4. The SCC in these same regions is 9.9, 50.4, 49.7, and 16.4 micro A cm2, respectively. 5. When short-circuited, net sodium and net chloride fluxes in the above regions are -0.36 and -0.27, 1.46*** and -0.92*, 1.74*** and -0.06 and 1.01*** and 0.07 mumol cm-2 h-1, respectively. Positive fluxes indicate net mucosal to serosal movements and asterisks indicate significant net fluxes (* P less than 0.05, *** P less than 0.001). 6. There is good agreement between the SCC and net sodium transport in R III B. In the other regions of the intestine the ionic basis of the SCC has not been completely explained. 7. The properties of the intestine in vitro appear to make the intestine well suited for the task of conserving sodium, a function which the intestine performs in vivo.