Response of rat jejunum to angiotensin III: pharmacology and mechanism of action.
At low doses angiotensin III (A III) stimulates jejunal fluid absorption in the pentobarbital sodium-anesthetized rat. In contrast, at high doses the hormone inhibits absorption and/or stimulates secretory processes. The stimulation of jejunal absorption in response to A III can be blocked by guanethidine, phentolamine, and prazosin but not by propranolol or yohimbine, suggesting that A III-increased intestinal absorption is secondary to the release of norepinephrine from sympathetic nerves in the jejunum and activation of postsynaptic alpha 1-adrenergic receptors. The A III inhibition of water absorption is not affected by adrenergic antagonists but can be reversed to a net stimulation of transfer after pretreatment of the animals with indomethacin. This suggests that at high doses A III stimulates intestinal prostaglandin biosynthesis. The A III analogue [Ile7]A III is devoid of agonist activity over a wide dose range and behaves as a potent antagonist of both the stimulatory and the inhibitory effects of the parent peptide on jejunal absorption. [Ile7]A III will be a useful tool for investigating the physiological role of angiotensin peptides in the control of intestinal absorption.
D000804:Angiotensin II / Q000031:analogs & derivatives* / Q000494:pharmacology; D000805:Angiotensin III / Q000494:pharmacology*; D000818:Animals; D001834:Body Water / Q000378:metabolism; D007408:Intestinal Absorption; D007444:Inulin; D007583:Jejunum / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008297:Male; D010646:Phentolamine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D015016:Yohimbine / Q000494:pharmacology
D000804:Angiotensin II; D000805:Angiotensin III; D015016:Yohimbine; D007444:Inulin; D011433:Propranolol; D011224:Prazosin; D010646:Phentolamine