Micropuncture evidence of rapid hydrolysis of bradykinin by rat proximal tubule
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Discussion
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Implication
Micropuncture study demonstrates rapid proximal tubular hydrolysis and reabsorption of bradykinin in rats, indicating luminal brush-border degradation controls renal peptide clearance.
Key Points
- To identify the specific tubular sites and enzymatic processes responsible for bradykinin metabolism and clearance in the mammalian nephron.
- Microinfused [3H]bradykinin and [14C]inulin simultaneously into proximal or distal tubules of Inactin-anesthetized rats, confirming puncture sites via neoprene microdissection.
- Assessed urinary recovery, tubular transit times, and resolved intact peptide from degradation products using two-dimensional peptide mapping.
- Urinary recovery of 3H label reached 24.1% after proximal tubule microinfusion compared with 98.0% following distal tubule microinfusion.
- Proximal urinary 3H activity comprised 85% metabolites (81% [3H]Pro and 4% [3H]Arg1-Phe5) and 15% intact bradykinin, whereas distal microinfusions yielded 100% intact bradykinin.
- Urinary recovery and metabolite distribution were independent of proximal tubular length, with excretion curves mirroring [14C]inulin transit profiles.
Cite This Study
Carone et al. (1976) studied this question.