Isolation and purification of angiotensin II using affinity and high-pressure liquid chromatography

Effect of contraceptive steroid and enalapril treatment of systolic blood pressure and plasma renin-angiotensin in the rat

Previous work has demonstrated contraceptive steroid-induced hypertension in rats. Here, we examined the relationship between steroid-induced hypertension and components of the renin-angiotensin system. Female Sprague-Dawley rats were injected s.c. with 0.2 micrograms ethynyloestradiol, 2.0 micrograms levonorgestrel, a combination of both or vehicle, six days per week. A second group of rats received 2.0 micrograms enalapril maleate, enalapril plus ethynyloestradiol or levonorgestrel, or vehicle. Systolic blood pressure increased with both ethynyloestradiol. (6 weeks, +17 mmHg; 12 weeks, +32 mmHg) and levonorgestrel (6 weeks, +24 mmHg) treatment. This effect of levonorgestrel was attenuated by co-administration of enalapril, which also reversed the hypertension seen with ethynyloestradiol. Ethynyloestradiol, but not levonorgestrel treatment caused a significant increase in plasma renin concentration, plasma renin activity, and plasma angiotensin II at both 6 and 12 weeks. Plasma renin substrate was increased by ethynyloestradiol at 3, 6 and 12 weeks, prior to the observed increase in systolic blood pressure. Combined steroid treatment had less pronounced effects. Enalapril alone or in combination with ethynyloestradiol decreased plasma renin concentration, activity and angiotensin II, and in combination with levonorgestrel decreased plasma renin concentration, substrate and activity (6 weeks only) but not angiotensin II. The data indicate a positive relationship between hypertension and the renin-angiotensin system with ethynyloestradiol, but not levonorgestrel treatment in rats.

Simplified method for quantitation of angiotensin peptides in tissue

A simple method for extraction, separation, identification and quantitation of angiotensin-like immunoactivity from tissue is described. Homogenized acetic acid extracts of tissue samples were lyophilized and reconstituted in mobile phase. Separation was performed by reversed-phase high-performance liquid chromatography on a phenyl silica gel column with an eluent consisting of 20% acetonitrile in 0.1 M aqueous ammonium phosphate buffer, pH 4.9. Elution of standard peptides under isocratic conditions revealed clear resolution of angiotensin I, II and III and the (1-7) and (3-8) peptides. Recoveries of labeled angiotensin peptide standards from the extraction step were > 90%. Radioimmunoassay of relevant peaks revealed detectable levels of angiotensin I-, II- and III-like immunoactivity in single rat hypothalami and brain stems.

Biosynthesis of angiotensinogen and angiotensins by brain cells in primary culture

This study focuses on the ability of primary rat brain cells in culture to synthesize angiotensinogen, angiotensin I, and angiotensin II. HPLC in combination with radioimmunoassay was used to characterize these compounds. Following incubation with 3H-labeled isoleucine, radioactively labeled angiotensinogen with an approximate molecular weight of 25,000 was identified in both glial and neuronal cells. Other molecular weight forms of angiotensinogen with molecular weights of about 300 and 160,000 were present in both cell types. In addition to angiotensinogen, radioactively labeled angiotensin I and angiotensin II were also synthesized by neuronal and glial cells. These results suggest that glial and neuronal cells can synthesize angiotensinogen, angiotensin I, and angiotensin II in a similar manner shown for the peripheral renin angiotensin system.