A sensitive radioimmunoassay method for urinary kinins in man

Area of Science:

• Biochemistry
• Nephrology
• Endocrinology

Background:

• Kinins are vasoactive peptides involved in blood pressure regulation.
• Previous methods for measuring urinary kinins lacked sensitivity and specificity.
• Accurate quantification of urinary kinins is crucial for understanding renal and hypertensive diseases.

Purpose of the Study:

• To develop a sensitive and specific radioimmunoassay for quantifying total urinary kinins.
• To assess urinary kinin levels in normal subjects and patients with chronic renal failure and essential hypertension.

Main Methods:

• Development of a radioimmunoassay using antiserum against synthetic bradykinin and labeled tyr8-bradykinin.
• Assay validation demonstrating high sensitivity (6 pg/tube) and specificity for bradykinin, lysyl-bradykinin, and methionyl-lysyl-bradykinin.
• Direct assay of unextracted urine samples, confirmed by chromatographic studies to eliminate interfering substances.

Main Results:

• The radioimmunoassay accurately detected total urinary kinins, with bradykinin, lysyl-bradykinin, and methionyl-lysyl-bradykinin showing similar dose-response curves.
• Urinary total kinin levels in normal male subjects were 37.9 ± 3.9 μg/day.
• Significantly reduced urinary kinin levels were observed in patients with chronic renal failure (9.0 ± 5.1 μg/day) and essential hypertension (24.2 ± 5.2 μg/day).

Conclusions:

• A validated radioimmunoassay provides a reliable method for measuring total urinary kinins.
• Urinary kinin levels are significantly diminished in patients with chronic renal failure and essential hypertension.
• These findings suggest a potential role for kinin deficiency in the pathogenesis of these conditions.