Local control of jejunal absorption by the renin-angiotensin system.

The purpose of this study was to determine if generation of angiotensin II (ANG II) locally within the intestine can influence ion and water absorption. Addition of ANG II to the serosal surface of isolated segments of rat jejunum significantly increased sodium and water absorption. Serosal addition of angiotensin III (ANG III) also increased jejunal absorption. Jejunum is the site of considerable angiotensinase activity. ANG III may thus mediate, at least in part, increased absorption in response to ANG II. Angiotensin I (ANG I) increased jejunal absorption. However, the increase in jejunal absorption following addition of ANG I could be prevented by inhibition of jejunal-converting enzyme. Thus, ANG I is without inherent activity to stimulate jejunal absorption. Intraperitoneal injection of a saline extract of rat kidney significantly stimulated jejunal absorption. Plasma and jejunal renin activity also increased in response to injection of kidney extract. The increase in jejunal absorption induced by kidney extract was not prevented by blockade of converting enzyme. Thus, ANG II may be generated by other enzyme pathways present in kidney homogenates. Alternatively, kidney may produce substances other than renin that are capable of influencing jejunal absorption.