SPECIFIC SUPERSENSITIVITY OF SMOOTH MUSCLE TO ANGIOTENSIN II AFTER NEPHRECTOMY

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Abstract
1 The dose-response curves for angiotensin, 5-hydroxytryptamine and carbachol were obtained on rat uterus and colon excised 24 h after a bilateral nephrectomy or a sham operation. 2 There was a shift to the left in the dose-response curves to angiotensin of organs from nephrectomized animals. Dose-response curves to 5-hydroxytryptamine and carbachol were not affected by nephrectomy. 3 The interaction of the two competitive antagonists (1-Asn, 5-Ileu, 8-Ala)-angiotensin II and (1-Asn, 5-Ileu, 8-Ileu)-angiotensin II with angiotensin II receptors was tested in control and nephrectomized organs. There was a decrease of the KI values in colon muscle after nephrectomy. 4 In conclusion, nephrectomy produces a specific supersensitivity to angiotensin that seems to be due to a change in the structure of angiotensin receptors, at least in colon smooth muscle. This increase in sensitivity may be the result of the elimination of a tropic factor that acts on angiotensin receptor sites.