Further studies on angiotensin tachyphylaxis.
Rabbit aorta and rat fundus do not display tachyphylaxis to angiotensin II (Asp1)angiotensin II) at 37 degrees C. These tissues do, however, display tachyphylaxis to [Sar1]angiotensin II (N-methylglycine 1 angiotensin II) and [dimethylglycine angiotensin II, respectively, at this temperature. At 22 degrees C, both tissues displayed rapid tachyphylaxis to [Asp1]angiotensin II which was reversed on prolonged incubation in peptide-free medium. At 37 degrees C, but at a lower than normal pH (pH 6.5 instead of 7.4), the rabbit aorta developed rapid tachyphylaxis to [Asp1)angiotensin II; this effect also was reversed on prolonged incubation in peptide-free medium. The rat uterus, at 30 degrees C, displayed tachyphylaxis to [Asp1]angiotensin II and analogs in order of rate of onset: [Sar1]angiotensin II greater than [Asp1]angiotensin II greater than [des-Asp1]angiotensin II. Over half of the individual uterine strips tested displayed no tachyphylaxis to [des-Asp1]angiotensin II. However, at 22 degrees C tachyphylaxis to all three compounds was rapid on onset and was reversed on prolonged incubation. The results indicate a correlation between affinity of the peptide analog for angiotensin receptor and its ability to induce tachyphylaxis. A possible involvement of membrane-bound enzymes in the onset and duration of tachyphylaxis is suggested.
Further studies on angiotensin tachyphylaxis. Rabbit aorta and rat fundus do not display tachyphylaxis to angiotensin II (Asp1)angiotensin II) at 37 degrees C. These tissues do, however, display tachyphylaxis to [Sar1]angiotensin II (N-methylglycine 1 angiotensin II) and [dimethylglycine angiotensin II, respectively, at this temperature. At 22 degrees C, both tissues displayed rapid tachyphylaxis to [Asp1]angiotensin II which was reversed on prolonged incubation in peptide-free medium. At 37 degrees C, but at a lower than normal pH (pH 6.5 instead of 7.4), the rabbit aorta developed rapid tachyphylaxis to [Asp1)angiotensin II; this effect also was reversed on prolonged incubation in peptide-free medium. The rat uterus, at 30 degrees C, displayed tachyphylaxis to [Asp1]angiotensin II and analogs in order of rate of onset: [Sar1]angiotensin II greater than [Asp1]angiotensin II greater than [des-Asp1]angiotensin II. Over half of the individual uterine strips tested displayed no tachyphylaxis to [des-Asp1]angiotensin II. However, at 22 degrees C tachyphylaxis to all three compounds was rapid on onset and was reversed on prolonged incubation. The results indicate a correlation between affinity of the peptide analog for angiotensin receptor and its ability to induce tachyphylaxis. A possible involvement of membrane-bound enzymes in the onset and duration of tachyphylaxis is suggested.