An angiotensin I-protein complex isolated by SDS-polyacrylamide gel electrophoresis from rat serum incubated with angiotensin I

Abstract

Angiotensin I (AI) protein complex with M_r 25,000 and an angiotensin I immunoreactive protein with M_r 60,000 were isolated from rat serum. The proteins were separated from AI by sodiumdodecylsulphate polyacrylamide gel electrophoresis under denaturing and reducing conditions using SDS and 2-mercaptoethanol (SDS-PAGE). The M_r 60,000 protein was isolated from non-incubated serum. Special attention was given to the M_r 25,000 AI-protein complex, called AI-25,000, which was generated in rat serum incubated with both synthetic and native AI for 1–5 h at 24°C and neutral pH. The AI-25,000 was determined in two radioimmunoassays using two anti-AI antisera and ¹²⁵I-AI. The experiments showed that AI reacts with a serum protein and forms a stable complex with a high molecular mass.

Key-words:

• generation of AI-protein complex
• native and synthetic angiotensin I
• radioimmunoassay
• serum