- Email: [email protected]
Is the central vasopressinergic system stimulated by angiotensin II?
POSTERS: Vasoactive Hormones/Autacoids
AIH 1999;12:58A-61A
E001
E002
IS THE CENTRAL VASOPKESSINERGIC SYSTEM STIMULATED BY ANGIOTENSIN II? F Muders, D Eisner, U Bahner, K Jandaleit, GAJ Riegger, M Palkovits. Klinik und Poliklinik flit lnnere Medizin II, University of Regensburg; Germany Vasopressin (ADH) is widely distributed in the brain and plays an important role in the central cardiovascular regulation by modulation of the baroreceptor reflex and the sympathetic nerve activity as well as by central pressor effects. AJagiotensin II (AII) is known to be a potent stimulus for ADH after central application. However, the action of high angiotensin II levels on the central ADH system has not investigated yet. Therefore, concentrations of ADH in 14 rnicrodissected brain areas were measured in rats treated with AII for ten days (!2 ttg All/kg BW/day S.C. by osmotic minipump). The treatment induced a significant increase of blood pressure (160 ± vs 100 ± mmHg; p<0.05) while the plasma levels of ADH remained unchanged (0.8 ±0.3 vs. 0.7 ± 0.2 pg/ml). In contrast, concentrations (pg/mg protein) of ADH decreased significantly in 5 of 14 brain areas, in those which are involved in central cardiovasscular regulation:
OUABAIN OR AN ISOMER IS ONE OF SEVERAL INHIBITORS OF Na-K.-ATPase IN HUMAN URINE. H.J. Kramer', A. B~icker, G. Krampitz, G. Pohlentz. Medical Policlinic and Department of Biochemistry, Univ. Bonn, FRG It is speculated that endogenous ouabain participates in the regulation of body fluid balance and arterial pressure. We therefore studied the nature of Na-K-ATPase inhibitors present in 24-h urines collected from healthy salt-loaded subjects. Pooled urines were lyophilized, redissolved and subjected to gel chromatography on Sephadex G-25 and G-10 and subsequently to RP-HPLC and thin layer chromatography. At all steps fractions were assayed for in vitro-inhibition of Na-K-ATPase and cress-reactivity with a ouabain antibody (NEN) (cressreaction with digoxin antibody was unrelated to enzyme inhibition). Only fractions showing Na-K-ATPase inhibition and cress-reaction with the ouabain antibody were subjected to mass spectroscopy before and after peracetylation. From the two fractions eluted from Sephadex G-10 the late fraction, when subjected to RP-HPLC, revealed a more apolar compound that was identified as vanadium diascorbate with Mr 403 and a more polar fraction that consisted mostly of inorganic material probably derived from complex salts with organic compounds such as V--diascorbate which is unstable when exposed to oxygen. A third more polar RP-HPLC compound, that was eluted from Sephadex G-10 in the fraction after void volume (in separate experiments added ouabain eluted in this fraction) strongly inhibited Na-K-ATPase and cross-reacted with the ouabain antibody. On mass spectroscopy this compound produced a small but unequivocal signal at Mr 584.3 identical to that of plant ouabain. Thus, there is strong evidence for the presence of ouabain or a ouabain-like compound in human urine besides other inhibitors of Na-K-ATPase such as vanadium diascorbate which might potentiate the renal effects of ouabain. These results confirm previous evidence for the presence of ouabain or an isomer in the mammalian organism. Its origin and its potential physiologic and pathophysiologic roles in body fluid and blood pressure regulation, however, remain to be determined. Key words: Human urine, Na-K-ATPase inhibitors, OLF
Paraventricular nucleus Median eminence Parafascieular nucleus Locus coerulens Subfornicial organ
CTRL 5395 + 117 23635 + 120 316 + 40 39 +3 51 5:5
AII 4268 + 109 14061 + 385 83 + 19 26 +5 17 + 3
p<0.Ol p<0.001 p
Conclusions: Circulating AII does not stimulate central and peripheral ADH but significantly stippressed ADH in specific brain areas. One of the target sites of the action could be the ADH-synthesizing neurons in the paraventricular nucleus which innervate the other 4 brain areas where ADH levels depleted in AII-treated rats. This effect, which is contrary to the effects of centrally applied ADH, may be explained by cardiovascular reflex suppression due to increased blood pressure.
Key Words:
brain nuclei, angiotensin II, hypertension, rat
E003
E004
EFFECT OF AGE ON RENAL RESPONSES TO COX-2 INHIBITORS, ROFECOXIB (VIOXXTM, MK-0966), CELECOXlB AND MELOXICAM, IN CONSCIOUS DOGS. P.K.S. Sieql, C.C. Chan, D.L. Bohn, R.M. Evans, P.B. Bunting, K.A. 6oper and D.H. Patrick. Merck Research Laboratories, West Point, PA 19486 and Merck Frosst Centre for Therapeutic Research, Kirkland, Quebec, Canada H9H 3L1. Prostaglandins formed via cyclooxygenase (COX) in the kidney play an important role in renal function via affects on vascular tone, glomerular filtration rate (GFR) and tubular function. Consequently, the most frequent renal side effects of COX inhibitors (e.g. nonsteroidal anti-inflammatory drugs, NSAIDS) are fluid and electrolyte imbalances. Studies to date indicate that selective COX-2 inhibitors have anti-inflammatory activity with an improved gastrointestinal safety profile. Both COX-1 and COX-2 isotorms are present in dog and human kidney. We compared the renal effects of three COX-2 inhibitors in conscious, female dogs (17-32 kg, 4 -12 yrs) to determine if they share the renal effects of NSAIDS. Their potencies on COX in whole blood assays are similar in dog (IC50values (p.M), COX1/COX-2: meloxicam 3.71/0.57, celecoxib 14.79/1.16, rofecoxib 37.11/0.25) and human. Rofecoxib is the most selective COX-2 inhibitor studied. Drugs were tested at oral doses that inhibit COX-2. Each drug produced a similar, modest decrease (11-23%) in urinary sodium excretion (UNaV) and urine flow (UVol) with no effect on GFR or effective renal plasma flow (ERPF). When data are analyzed by age, significant decreases in UNaV,GFR, UVol and ERPF are observed in older (> 10 yrs), but not younger (< 7 yrs) dogs. The magnitude of renal responses was not different among meloxicam, celecoxib and rofecoxib suggesting that the mechanism is selective COX-2 inhibition. Predrug indices of renal function differed between young and old dogs in that UVol, GFR and ERPF were greater in older dogs. An enhanced role for COX-2 in the kidney with age could be due to up-regulation of COX-2, decline in renal function or combination of both. In conclusion, rofecoxib, celecoxib and meloxicam showed identical propensities for reducing renal function in older dogs. Key Words: prostaglandins,kidney, rofecoxib, celecoxib and meloxicam
RECEPTOR-MEDIATED VASODILATION EFFECT OF ANGIOTENSIN 1-7(Ang 1-7) IN THE ISOLATED RABBIT AFFERENT ARTERIOLE (Af-Art) Y. Ren, J.U Garvin and O.A. Carretero Henry Ford Hospital, Detroit, MI 48202 We have previously reported that Ang 1-7 caused vasodilation in isolated Af-Arts via NO. We now hypothesize that Ang 1-7-induced release of NO is mediated by a non AT1, non AT2 receptor. Af-Arts were preconstricted with norepinephrine, which decreased diameter from 19.0 + 0.9 to 8.9 + 1.0 pro, and increasing concentrations of Ang 1-7 added to the lumen. Ang 1-7 produced dose-dependent vasodilation, increasing luminal diameter to 12.1 + 1.2" (10-9 M), 14.5 + 0.8* (10"s M), 16.2 + 0.9* (10"7 M), and 16.4 + 1.0" (10.8 M) pm (n = 10; *p < 0.01). We next studied the angiotensin receptor subtype involved. 10.6 M [7-D-Ala]-Ang 1-7, a potent and selective Ang 1-7 antagonist, abolished the dilation induced by Ang 1-7 (n = 6). The diameter of preconstricted Af-At in the presence of [7-D-Ala]-Ang 1-7 was 10.2 ± 1.2 pm, and 9.2 + 1.0 pm after 106 M Ang 1-7 was added to the lumen. Both an AT1 receptor antagonist (L158809) and an AT2 receptor antagonist (PD123319) at 10.6 M had no effect on Ang 1-7-induced dilation, while 104 M Ang 1-7 increased diameter of preconstricted vessels from 8.8 + 1.9 to 18.3 + 1.8" pm (n = 6; p < 0.01) and from 9.6 + 1.5 to 17.8 + 1.1" pm (n = 7; p < 0.01), respectively. Our results demonstrate that Ang 1-7 has a receptormediated vasodilator effect on the rabbit Af-Art. This effect may be mediated by Ang 1-7 receptors, since AT1 and AT2 receptor antagonists could not block Ang 1-7-induced dilation. This suggests that Ang 1-7 opposes the action of Ang II and plays an important role in regulation of renal hemodynamics. Key Words: Ang 1-7, afferent arteriole, antagonist
AIH 1999;12:58A-61A
E001
E002
IS THE CENTRAL VASOPKESSINERGIC SYSTEM STIMULATED BY ANGIOTENSIN II? F Muders, D Eisner, U Bahner, K Jandaleit, GAJ Riegger, M Palkovits. Klinik und Poliklinik flit lnnere Medizin II, University of Regensburg; Germany Vasopressin (ADH) is widely distributed in the brain and plays an important role in the central cardiovascular regulation by modulation of the baroreceptor reflex and the sympathetic nerve activity as well as by central pressor effects. AJagiotensin II (AII) is known to be a potent stimulus for ADH after central application. However, the action of high angiotensin II levels on the central ADH system has not investigated yet. Therefore, concentrations of ADH in 14 rnicrodissected brain areas were measured in rats treated with AII for ten days (!2 ttg All/kg BW/day S.C. by osmotic minipump). The treatment induced a significant increase of blood pressure (160 ± vs 100 ± mmHg; p<0.05) while the plasma levels of ADH remained unchanged (0.8 ±0.3 vs. 0.7 ± 0.2 pg/ml). In contrast, concentrations (pg/mg protein) of ADH decreased significantly in 5 of 14 brain areas, in those which are involved in central cardiovasscular regulation:
OUABAIN OR AN ISOMER IS ONE OF SEVERAL INHIBITORS OF Na-K.-ATPase IN HUMAN URINE. H.J. Kramer', A. B~icker, G. Krampitz, G. Pohlentz. Medical Policlinic and Department of Biochemistry, Univ. Bonn, FRG It is speculated that endogenous ouabain participates in the regulation of body fluid balance and arterial pressure. We therefore studied the nature of Na-K-ATPase inhibitors present in 24-h urines collected from healthy salt-loaded subjects. Pooled urines were lyophilized, redissolved and subjected to gel chromatography on Sephadex G-25 and G-10 and subsequently to RP-HPLC and thin layer chromatography. At all steps fractions were assayed for in vitro-inhibition of Na-K-ATPase and cress-reactivity with a ouabain antibody (NEN) (cressreaction with digoxin antibody was unrelated to enzyme inhibition). Only fractions showing Na-K-ATPase inhibition and cress-reaction with the ouabain antibody were subjected to mass spectroscopy before and after peracetylation. From the two fractions eluted from Sephadex G-10 the late fraction, when subjected to RP-HPLC, revealed a more apolar compound that was identified as vanadium diascorbate with Mr 403 and a more polar fraction that consisted mostly of inorganic material probably derived from complex salts with organic compounds such as V--diascorbate which is unstable when exposed to oxygen. A third more polar RP-HPLC compound, that was eluted from Sephadex G-10 in the fraction after void volume (in separate experiments added ouabain eluted in this fraction) strongly inhibited Na-K-ATPase and cross-reacted with the ouabain antibody. On mass spectroscopy this compound produced a small but unequivocal signal at Mr 584.3 identical to that of plant ouabain. Thus, there is strong evidence for the presence of ouabain or a ouabain-like compound in human urine besides other inhibitors of Na-K-ATPase such as vanadium diascorbate which might potentiate the renal effects of ouabain. These results confirm previous evidence for the presence of ouabain or an isomer in the mammalian organism. Its origin and its potential physiologic and pathophysiologic roles in body fluid and blood pressure regulation, however, remain to be determined. Key words: Human urine, Na-K-ATPase inhibitors, OLF
Paraventricular nucleus Median eminence Parafascieular nucleus Locus coerulens Subfornicial organ
CTRL 5395 + 117 23635 + 120 316 + 40 39 +3 51 5:5
AII 4268 + 109 14061 + 385 83 + 19 26 +5 17 + 3
p<0.Ol p<0.001 p
Conclusions: Circulating AII does not stimulate central and peripheral ADH but significantly stippressed ADH in specific brain areas. One of the target sites of the action could be the ADH-synthesizing neurons in the paraventricular nucleus which innervate the other 4 brain areas where ADH levels depleted in AII-treated rats. This effect, which is contrary to the effects of centrally applied ADH, may be explained by cardiovascular reflex suppression due to increased blood pressure.
Key Words:
brain nuclei, angiotensin II, hypertension, rat
E003
E004
EFFECT OF AGE ON RENAL RESPONSES TO COX-2 INHIBITORS, ROFECOXIB (VIOXXTM, MK-0966), CELECOXlB AND MELOXICAM, IN CONSCIOUS DOGS. P.K.S. Sieql, C.C. Chan, D.L. Bohn, R.M. Evans, P.B. Bunting, K.A. 6oper and D.H. Patrick. Merck Research Laboratories, West Point, PA 19486 and Merck Frosst Centre for Therapeutic Research, Kirkland, Quebec, Canada H9H 3L1. Prostaglandins formed via cyclooxygenase (COX) in the kidney play an important role in renal function via affects on vascular tone, glomerular filtration rate (GFR) and tubular function. Consequently, the most frequent renal side effects of COX inhibitors (e.g. nonsteroidal anti-inflammatory drugs, NSAIDS) are fluid and electrolyte imbalances. Studies to date indicate that selective COX-2 inhibitors have anti-inflammatory activity with an improved gastrointestinal safety profile. Both COX-1 and COX-2 isotorms are present in dog and human kidney. We compared the renal effects of three COX-2 inhibitors in conscious, female dogs (17-32 kg, 4 -12 yrs) to determine if they share the renal effects of NSAIDS. Their potencies on COX in whole blood assays are similar in dog (IC50values (p.M), COX1/COX-2: meloxicam 3.71/0.57, celecoxib 14.79/1.16, rofecoxib 37.11/0.25) and human. Rofecoxib is the most selective COX-2 inhibitor studied. Drugs were tested at oral doses that inhibit COX-2. Each drug produced a similar, modest decrease (11-23%) in urinary sodium excretion (UNaV) and urine flow (UVol) with no effect on GFR or effective renal plasma flow (ERPF). When data are analyzed by age, significant decreases in UNaV,GFR, UVol and ERPF are observed in older (> 10 yrs), but not younger (< 7 yrs) dogs. The magnitude of renal responses was not different among meloxicam, celecoxib and rofecoxib suggesting that the mechanism is selective COX-2 inhibition. Predrug indices of renal function differed between young and old dogs in that UVol, GFR and ERPF were greater in older dogs. An enhanced role for COX-2 in the kidney with age could be due to up-regulation of COX-2, decline in renal function or combination of both. In conclusion, rofecoxib, celecoxib and meloxicam showed identical propensities for reducing renal function in older dogs. Key Words: prostaglandins,kidney, rofecoxib, celecoxib and meloxicam
RECEPTOR-MEDIATED VASODILATION EFFECT OF ANGIOTENSIN 1-7(Ang 1-7) IN THE ISOLATED RABBIT AFFERENT ARTERIOLE (Af-Art) Y. Ren, J.U Garvin and O.A. Carretero Henry Ford Hospital, Detroit, MI 48202 We have previously reported that Ang 1-7 caused vasodilation in isolated Af-Arts via NO. We now hypothesize that Ang 1-7-induced release of NO is mediated by a non AT1, non AT2 receptor. Af-Arts were preconstricted with norepinephrine, which decreased diameter from 19.0 + 0.9 to 8.9 + 1.0 pro, and increasing concentrations of Ang 1-7 added to the lumen. Ang 1-7 produced dose-dependent vasodilation, increasing luminal diameter to 12.1 + 1.2" (10-9 M), 14.5 + 0.8* (10"s M), 16.2 + 0.9* (10"7 M), and 16.4 + 1.0" (10.8 M) pm (n = 10; *p < 0.01). We next studied the angiotensin receptor subtype involved. 10.6 M [7-D-Ala]-Ang 1-7, a potent and selective Ang 1-7 antagonist, abolished the dilation induced by Ang 1-7 (n = 6). The diameter of preconstricted Af-At in the presence of [7-D-Ala]-Ang 1-7 was 10.2 ± 1.2 pm, and 9.2 + 1.0 pm after 106 M Ang 1-7 was added to the lumen. Both an AT1 receptor antagonist (L158809) and an AT2 receptor antagonist (PD123319) at 10.6 M had no effect on Ang 1-7-induced dilation, while 104 M Ang 1-7 increased diameter of preconstricted vessels from 8.8 + 1.9 to 18.3 + 1.8" pm (n = 6; p < 0.01) and from 9.6 + 1.5 to 17.8 + 1.1" pm (n = 7; p < 0.01), respectively. Our results demonstrate that Ang 1-7 has a receptormediated vasodilator effect on the rabbit Af-Art. This effect may be mediated by Ang 1-7 receptors, since AT1 and AT2 receptor antagonists could not block Ang 1-7-induced dilation. This suggests that Ang 1-7 opposes the action of Ang II and plays an important role in regulation of renal hemodynamics. Key Words: Ang 1-7, afferent arteriole, antagonist