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- Title
Reaction constants of renin in juxtaglomerular apparatus and plasma renin activity after renal ischemia and hemorrhage.
- Authors
Weber, Peter; Held, Eckhard; Uhlich, Eike; Eigler, Jochen O. C.
- Abstract
During and after total renal ischemia and acute hemorrhage, renin activity in plasma (PRA) and microdissected juxtaglomerular apparatus (JGA) of rabbits were investigated. In controls, the apparent Michaelis-Menten constant (MMC) of semipurified standard renin or rabbits was 1025 ± 233 SD ng/ml. Plasma renin of normal rabbits showed similar values: 1062 ± 138 SD ng/ml. Intrarenal JGA renin, however, showed a great scatter of MMC (920 to 4760 ng/ml) and a significantly higher mean value of 2572 ± 1156 SD ng/ml (P < 0.001). After complete renal ischemia by clamping both renal arteries for a 90-min period, the following results were obtained: 1) Sixty min after the beginning of ischemia, PRA decreased from 20.9 ± 9.8 SD to 7.6 ± 5.2 SD ng/ml·hr (P < 0.05) and increased to 103, 6K and 42 ng/ml· hr 10, 30 and 90 min after removal of the clamps, respectively (P < 0.05). 2) No significant change of JGA renin concentration was found 0 to 72 hr after ischemia (68.5 ± 73.0 to 65.6± 49.0; P > 0.1). 3) JGA renin activity increased significantly as indicated by a decrease of MMC from 2620 ± 1091 SD to 1305 ± 429 SD ng/ml, 30 to 90 min after ischemia (P < 0.002). After lowering mean arterial blood pressure from 85 ± 10 SD to 40 ± 16 SD mm Hg by acute hemorrhage, the following findings were registered: 1) PRA rose significantly from 18.1 ± 10.5 SD to 81.2 ± 35.6 ng/ml· hr (P < 0.001) and reached control values after retransfusion. 2) JGA renin concentration decreased from 89.4 ± 42.1 SD to 45.2 ± 36.4 SD ng/100 μl · hr per single JGA (P < 0.01). 3) The MMC of JGA renin decreased from 2620 ± 1091 SD to 1444 ± 358 SD ng/ml (P < 0.002). This suggests a transformation of JGA renin to a higher affinity form by these maneuvers. Our results indicate that, in addition to increased renin release into the systemic circulation, JGA renin activity is increased after renal ischemia and acute hemorrhage; this activation is not mediated by an elevation of enzyme concentration but by a decrease of MMC.
- Subjects
RENIN; JUXTAGLOMERULAR apparatus; HEMORRHAGE; ISCHEMIA; BLOOD circulation disorders; BLOOD vessels
- Publication
Kidney International, 1975, Vol 7, Issue 1, p331
- ISSN
0085-2538
- Publication type
Article
- DOI
10.1038/ki.1975.46