Radioimmunoassay of Rat Submandibular Gland Kallikrein and the Detection of Immunoreactive Antigen on Blood

Abstract

Glandular kallikreins are a group of related kinin-forming enzymes (EC 3.4.21.8) present in the major exocrine glands and in the kidney. They are found in the ductal cells of the salivary glands, in the distal tubular cells of the kidney and in the acini of the pancreas (Nustad et al., 1978b). After activation of the glands, kallikrein is found in the secreted fluids such as saliva, pancreatic juice and distal tubular urine. However, evidence indicate that glandular kallikreins may be released to blood during salivary gland stimulation (Nustad et al., 1978b). The substrate for glandular kallikreins is present mainly in blood and formation of the active product lysyl-bradykinin implies that enzyme and substrate combines in the intercellular space or in blood. However, so far glandular kallikreins have not been detected in blood except during acute pancreatitis where an inhibitor-pancreatic kallikrein complex was found (Ofstad, 1970). The establishment of a sensitive radioimmunoassay for glandular kallikreins has allowed us to explore the possible occurrence of glandular kallikreins in blood. Employing antiserum raised against purified rat submandibular gland kallikrein, we demonstrate the presence of immunological crossreacting material(s) in plasma. A preliminary report was presented at the Nordic Micro-circulation group (Nustad et al., 1978a; Ørstavik et al., 1978).