Influence of reproductive state on intestinal fluid and ion transport by the rat jejunum, in relation to the possible contribution of prolactin.

Mucosal fluid, sodium and chloride transfer by the rat jejunum was higher at pro-oestrus and oestrus than at dioestrus. Prolactin enhanced intestinal absorption in dioestrous but not in oestrous rats. Ovariectomy had no significant effect on fluid and sodium absorption but resulted in increased chloride absorption. Oestrogen treatment, however, stimulated fluid and sodium transport without affecting chloride absorption in ovariectomized rats. In contrast, progesterone had no influence on fluid and sodium transport but inhibited chloride absorption. Intestinal absorption of fluid, sodium chloride, potassium, calcium and magnesium was significantly increased during pregnancy and lactation. The limited effect of 2-Br-alpha-ergocryptine in depressing intestinal absorption of fluid and NaCl in both pregnant and lactating rats suggests that hormones other than prolactin are also involved. Lactating rats not suckled for 24 h, or subjected to reduction in the number of pups from eight to three, did not show major changes in intestinal absorption of fluid and NaCl. The present data suggest that increases in intestinal transport during oestrus, pregnancy and lactation are attributable to hormonal changes to which prolactin may make an important contribution.