New trypsin-releasable spasmogenic substances in the plasma of spontaneously hypertensive rats

We measured the levels of trypsin-releasable spasmogenic substances (TRSS) in the plasma of spontaneously hypertensive rats (SHR) during the development of hypertension. TRSS levels (means +/- SEM, N = 4) were significantly higher at 12 weeks (7.13 +/- 1.05 micrograms bradykinin equivalents (BKE)/ml plasma) and 24 weeks (6.87 +/- 0.60 micrograms BKE/ml) compared to 8 weeks (3.3 +/- 0.55 micrograms BKE/ml) and to normotensive Wistar Kyoto (WKN) rats, whose levels were 3.74 +/- 0.74 micrograms BKE/ml at 24 weeks and did not change significantly during the period studied. The mean arterial pressure (MAP) of SHR was 150-170, 160-180 and 170-220 mmHg at 8, 12 and 24 weeks, respectively, whereas the WKN MAP was 110-120 mmHg at 24 weeks. The increase in total TRSS was due to substances which elicit the slow contraction of the isolated guinea pig ileum and which could be distinguished from BK, T-kinin and other BK homologues by gel filtration on Sephadex G-25, gradient elution chromatography on CM-cellulose and by the slow rate of contraction of the guinea pig ileum. All of these properties are the same as those we have previously demonstrated for TRSS of Goldblatt 1-kidney 1-clip renal hypertensive rats and which are due, at least in part, to a 14 amino acid peptide whose composition does not correspond to any known spasmogenic substance.