Interaction between alpha 2-adrenergic and angiotensin II systems in the control of glomerular hemodynamics as assessed by renal micropuncture in the rat.

Abstract

The hypothesis that renal a2 adrenoceptors influence nephron filtration rate (SNGFR) via interaction with angiotensin II (All) was tested by renal micropuncture. The physical determinants of SNGFR were assessed in adult male Munich Wistar rats 5-7 d after ipsilateral surgical renal denervation (DNX). DNX was performed to isolate inhibitory central and presynaptic a2 adrenoceptors from end-organ receptors within the kidney. Two experimental protocols were employed: one to test whether prior All receptor blockade with saralasin would alter the glomerular hemodynamic response to a2 adrenoceptor stimulation with the selective agonist B-HT 933 under euvolemic conditions, and the other to test whether B-HT 933 would alter the response to exogenous All under conditions of plasma volume expansion. In euvolemic rats, B-HT 933 caused SNGFR to decline as the result of a decrease in glomerular ultrafiltration coefficient (LpA), an effect that was blocked by saralasin. After plasma volume expansion, B-HT 933 showed no primary effect on LpA but heightened the response of arterial blood pressure, glomerular transcapillary pressure gradient, and LpA to All. The parallel results of these converse experiments suggest a complementary interaction between renal a2-adrenergic and All systems in the control of LpA. (J. Clin. Invest. 1992.

Agmatine, a bioactive metabolite of arginine. Production, degradation, and functional effects in the kidney of the rat.

“…These animals express at least 20 glomeruli on the exposed micropuncture surface. Animals were anesthetized (Inactin; 100 mg/kg) and prepared for surgery as previously described with catheters in the jugular vein and femoral artery and bladder (25)(26)(27). After preliminary surgery the kidney was dissected free from the adrenal gland and perirenal fat via a left subcostal incision.…”

“…A sustaining infusion of 1.5 ml/h isotonic saline containing 3 H inulin was supplied to deliver ‫ف‬ 60-80 Ci/h for single nephron glomerular filtration rate (SNGFR) and APR measurements. Animals also received littermate plasma infusion (1% TBW in 60 min followed by 0.15%TBW/h) Certain studies were performed in rats which were previously submitted to left unilateral renal denervation as previously described (26,27), 5-7 d before micropuncture studies.…”

“…Inulin clearance (UV/P) and volumetric measurement of fluid collected from late proximal tubules were employed to calculate SNGFR and APR. Single nephron plasma flow (SNPF) was also determined (25)(26)(27) in interstitial infusion studies whereby a micro-adaptation of the Lowry technique (30) was employed to determine the protein concentrations of systemic (C A ) and efferent arteriolar (C E ) plasma. The determinants of SNPF were; SNPF ϭ (SNGFR*C E /(C E Ϫ C A )].…”

“…The determinants of SNPF were; SNPF ϭ (SNGFR*C E /(C E Ϫ C A )]. To take best advantage of the paired nature of the experiments, the effects of treatments were analyzed by one-way ANOVA with design for repeated measures as described previously (27).…”

Vascular Biology: Relevance of Nitric Oxide in Vascular and Nonvascular Tissue with Normal and Decreased Renal Function

“…Prior denervation consistently produces an increase in the number of angiotensin II receptors [16]. This may be due to changes in a2-adrenergic receptor activity within the kidney which somehow modifies the number of angiotensin II receptors [17,18]. It is clear that not only does the angiotensin II system interact with 32 Blanlz Biology of Nitric Oxide NO but, in addition, the adrenergic nervous system.…”