Connecting tubule glomerular feedback antagonizes tubuloglomerular feedback in vivo.

In vitro experiments showed that the connecting tubule (CNT) sends a signal that dilates the afferent arteriole (Af-Art) when Na(+) reabsorption in the CNT lumen increases. We call this process CNT glomerular feedback (CTGF) to differentiate it from tubuloglomerular feedback (TGF), which is a cross talk between the macula densa (MD) and the Af-Art. In TGF, the MD signals the Af-Art to constrict when NaCl transport by the MD is enhanced by increased luminal NaCl. CTGF is mediated by CNT Na(+) transport via epithelial Na(+) channels (ENaC). However, we do not know whether CTGF occurs in vivo or whether it opposes the increase in Af-Art resistance caused by TGF. We hypothesized that CTGF occurs in vivo and opposes TGF. To test our hypothesis, we conducted in vivo micropuncture of individual rat nephrons, measuring stop-flow pressure (P(SF)) as an index of glomerular filtration pressure. To test whether activation of CTGF opposes TGF, we used benzamil to block CNT Na(+) transport and thus CTGF. CTGF inhibition with the ENaC blocker benzamil (1 µM) potentiated the decrease in P(SF) at 40 and 80 nl/min. Next, we tested whether we could augment CTGF by inhibiting NaCl reabsorption in the distal convoluted tubule with hydrochlorothiazide (HCTZ, 1 mM) to enhance NaCl delivery to the CNT. In the presence of HCTZ, benzamil potentiated the decrease in P(SF) at 20, 40, and 80 nl/min. We concluded that in vivo CTGF occurs and opposes the vasoconstrictor effect of TGF.

Relation between structure and correcting activity of bovine high molecular weight kininogen upon the clotting time of Fitzgerald-trait plasma.

Bovine high molecular weight kininogen (bHMWK) partially corrects the activated plasma thromboplastin time (aPTT) of Fitzgerald trait plasma which is congenitally deficient in HMWK. The relationship between the structure and activity of HMWK was clarified by studying the effects of different fragments of bHMWK on the aPTT of Fitzgerald-trait plasma. The peptides studied were lys-bradykinin-free HMWK, bradykinin-fragment 1-2-free HMWK, heavy chain, fragment 1-2-light chain, and light chain. All fragments were tested in equimolar concentrations. Bradykinin-fragment 1-2-free HMWK, heavy chain, and light chain have little or no correcting activity upon Fitzgerald-trait plasma aPTr. Fragment 1-2 light chain has the same correcting activity as intact bHMWK, while that of lys-bradykinin-free HMWK appears to be higher. Both fragment 1-2 and fragment 2 inhibit the clotting time of normal human plasma. When compared on a molar basis, fragment 2 is a more active inhibitor than fragment 1-2. When the effects of bovine plasma kallikrein upon bHMWK and hHMWK were studied, it was found that it released kinins from both kininogens. However, while the correcting activity of bHMWK was completely destroyed after 60 min of incubation, that of hHMWK was fully retained. These data suggest that: (a) the active part of bHMWK is comprised of the fragment 1-2 light chain portion; (b) fragment 1-2 or fragment 2 is the binding site to negatively charged surfaces, while the light chain interacts with other components of the surface-mediated reactions; and (c) bovine plasma kallikrein releases kinins, but probably does not cause the release of fragment 1-2 from human HMWK.

Uncommon case of Mycobacterium bovis brain abscess complicated by suppurative fistula, and review of the literature. / Caso insólito de absceso cerebral por Mycobacterium bovis complicado con fístula supurativa y revisión de la bibliografía.

INTRODUCTION: Mycobacterium bovis is an infrequent cause of central nervous system tuberculosis in Spain, with few cases described in the literature. Since compulsory pasteurization of milk and implementation of eradication programs on infected cattle, human sporadic illness with this organism has dramatically declined in developed countries. CASE REPORT: A 71-year-old immunocompromised male, who presented a calvarial lytic lesion. A craniotomy for the total resection of the lesion was performed and the microbiology results were positive for M. bovis, therefore antituberculous therapy was initiated. Despite of the correct treatment, the patient developed a tuberculous abscess that required an aggressive surgical management followed by a suppurative fistula. Based on the treatment of tuberculous lymphadenitis, we decided to perform a conservative management with antituberculous therapy (isoniazid + rifampicin + ethambutol + moxifloxacin + steroids during 12 months) and avoided new surgical cleanings of the surgical bed obtaining a good response and a good clinical evolution. CONCLUSIONS: As far as we know, this is the first case reported of a suppurative fistula after the resection of a cerebral abscess caused by M. bovis, therefore, there is no report in the literature about the treatment of this complication.

TITLE: Caso insólito de absceso cerebral por Mycobacterium bovis complicado con fístula supurativa y revisión de la bibliografía.Introducción. Mycobacterium bovis es una causa infrecuente de tuberculosis del sistema nervioso central en España, del cual existen pocos casos descritos en la bibliografía. Desde la pasteurización obligatoria de la leche y la implementación de programas de erradicación del ganado infectado, la enfermedad esporádica humana con este organismo ha disminuido drásticamente en los países desarrollados. Caso clínico. Varón inmunoafectado de 71 años, que presentaba una lesión lítica esporádica en la calota. Se realizó una craneotomía de la lesión y los resultados de microbiología fueron positivos para M. bovis, por lo que se inició tratamiento con terapia antituberculosa. A pesar del tratamiento correcto, el paciente desarrolló un absceso tuberculoso, que requirió un tratamiento quirúrgico agresivo, seguido de una complicación con una fístula supurativa. Sobre la base del tratamiento descrito para la linfadenitis tuberculosa, se decidió realizar un tratamiento conservador de la fístula supurativa, sin realizar nuevas limpiezas del lecho quirúrgico, y mantener de manera prolongada la terapia antituberculosa (isoniacida + rifampicina + etambutol + moxifloxacino + esteroides durante 12 meses), con lo que presentó una buena evolución clínica. Conclusiones. Hasta la fecha, éste es el primer caso descrito de una fístula supurativa después de la resección de un absceso cerebral causado por M. bovis, por lo que no existe en la bibliografía artículo alguno que describa el tratamiento adecuado de esta complicación.

Synthetic microfibers in the marine environment: A review on their occurrence in seawater and sediments.

The objective of this review is to summarize information on microfibers in seawater and sediments from available scientific information. Microfibers were found in all reviewed documents. An heterogeneous approach is observed, with regard to sampling methodologies and units. Microfibers in sediments range from 1.4 to 40 items per 50mL or 13.15 to 39.48 items per 250g dry weight. In the case of water, microfibers values ranges from 0 to 450items·m-3 or from 503 to 459,681items·km-2. Blue is the most common color in seawater and sediments, followed by transparent and black in the case of seawater, and black and colorful in sediments. Related with polymer type, polypropylene is the most common in water and sediments, followed by polyethylene in water and polyester in water and sediments. Some polymers were described only in water samples: high-density polyethylene, low-density polyethylene and cellophane, whilst only rayon was reported in sediments.

Modulation of angiotensin II-induced vasoconstriction by endothelium-derived relaxing factor in the isolated microperfused rabbit afferent arteriole.

Although endothelium-derived relaxing factor (EDRF) has been studied extensively in large vessels, little is known about its role in the preglomerular afferent arteriole (Af-Art). We tested the hypothesis that EDRF, which is produced locally in the Af-Art, modulates arteriolar responses to angiotensin II (AII). A single rabbit Af-Art with its glomerulus intact was microperfused in vitro at 60 mmHg. When 0.1 microM AII was first applied, luminal diameter decreased by 49 +/- 7.0% (n = 9; P less than 0.0001); however, constriction waned, with the decrease becoming 15 +/- 3.5% at 1 min. After washing the Af-Art, repeated AII caused less constriction (13 +/- 4.0%; P less than 0.0002 vs. first application), showing tachyphylaxis. Pretreatment with Nw-nitro-L-arginine (N-Arg), which inhibits synthesis of nitric oxide (an EDRF), decreased basal diameter by 18 +/- 3.0% (n = 14; P less than 0.0001). N-Arg also augmented AII-induced constriction (86 +/- 6.8%; P less than 0.02 vs. nontreated Af-Art) and rendered it persistent (82 +/- 6.9% at 1 min). Even after pretreatment with N-Arg, repeated AII caused a weaker response, which was restored by washing with kidney homogenate rich in angiotensinase. In conclusion, this study provides evidence that local production of EDRF is an important determinant of the tone of the Af-Art. Our results suggest that the transient nature of AII-induced constriction of the Af-Art may be due to production of EDRF, while tachyphylaxis may be the result of long lasting receptor occupancy.

Possible role of adenosine in the macula densa mechanism of renin release in rabbits.

This study was designed to examine: (a) the effects of adenosine and its analogues on renin release in the absence of tubules, glomeruli, and macula densa, and (b) whether adenosine may be involved in a macula densa-mediated renin release mechanism. Rabbit afferent arterioles (Af) alone and afferent arterioles with macula densa attached (Af + MD) were microdissected and incubated for two consecutive 30-min periods. Hourly renin release rate from a single arteriole (or an arteriole with macula densa) was calculated and expressed as ng AI X h-1 X Af-1 (or Af + MD-1)/h (where AI is angiotensin I). Basal renin release rate from Af was 0.69 +/- 0.09 ng AI X h-1 X Af-1/h (means +/- SEM, n = 16) and remained stable for 60 min. Basal renin release rate from Af + MD was 0.20 +/- 0.04 ng AI X h-1 X Af + MD-1/h (n = 6), which was significantly lower (P less than 0.0025) than that from Af. When adenosine (0.1 microM) was added to Af, renin release decreased from 0.72 +/- 0.16 to 0.24 +/- 0.04 ng AI X h-1 X Af-1/h (P less than 0.025; n = 9). However, when adenosine was added to Af + MD, no significant change in renin release was observed. N6-cyclohexyl adenosine (an A1 adenosine receptor agonist) at 0.1 microM decreased renin release from Af from 0.69 +/- 0.14 to 0.39 +/- 0.12 ng AI X h-1 X Af-1/h (n = 5, P less than 0.05). However, 5'-N-ethylcarboxamide adenosine (an A2 adenosine receptor agonist) either at 0.1 microM or at 10 microM had no effect. Theophylline, at a concentration (10 microM) that does not block phosphodiesterase but does block adenosine receptors, increased renin release from Af + MD from 0.21 +/- 0.03 to 0.46 +/- 0.08 ng AI X h-1 X Af + MD-1/h (P less than 0.05; n = 8). The results are consistent with the hypotheses that adenosine decreases renin release via the activation of A1 adenosine receptors, and that adenosine may be an inhibitory signal from the macula densa to juxtaglomerular cells.

Endothelium-derived relaxing factor/nitric oxide modulates angiotensin II action in the isolated microperfused rabbit afferent but not efferent arteriole.

It has been reported that sensitivity to angiotensin II (Ang II) is higher in efferent (Ef) than afferent (Af) arterioles (Arts). We tested the hypothesis that this is due to arteriolar differences in the interaction between Ang II and endothelium-derived relaxing factor/nitric oxide (EDNO). Rabbit Af-Arts with glomerulus intact were microperfused in vitro at a constant pressure. Ef-Arts were perfused from the distal end of either the Af-Art (orthograde perfusion) or the Ef-Art (retrograde perfusion) to eliminate influences of the Af-Art or glomerulus, respectively. Ang II did not alter Af-Art luminal diameter until the concentration reached 10(-9) M, which decreased the diameter by 11 +/- 2.6% (n = 11; P < 0.002). In contrast, Ef-Arts became significantly constricted at concentrations as low as 10(-11) M with either perfusion. Surprisingly, the decrease in Ef-Art diameter at 10(-10), 10(-9), and 10(-8) M was significantly greater with retrograde perfusion (44 +/- 6.9%, 70 +/- 5.6%, and 74 +/- 4.1%, respectively; n = 5) than with orthograde perfusion (16 +/- 4.2%, 25 +/- 2.9%, and 35 +/- 3.5%; n = 9). ENDO synthesis inhibition with 10(-4) M nitro-L-arginine methyl ester (L-NAME) decreased the diameter to a greater extent in Af-Arts (22 +/- 3.0%; n = 11) compared to Ef-Arts with either orthograde (9.5 +/- 2.3%; n = 8) or retrograde perfusion (1.2 +/- 2.1%; n = 6). With L-NAME pretreatment, Af-Art constriction induced by 10(-10) M (14 +/- 4.0%, n = 9) and 10(-9) M Ang II (38 +/- 3.9%) was significantly greater compared to nontreated Af-Arts. In contrast, L-NAME pretreatment had no effect on Ang II-induced constriction in Ef-Arts with either perfusion. In conclusion, this study demonstrates higher sensitivity of Ef-Arts to Ang II, particularly with retrograde perfusion. Our results suggest that EDNO significantly modulates the vasoconstrictor action of Ang II in Af-Arts II but not Ef-Arts, contributing to the differential sensitivity to Ang II.

Flow modulates myogenic responses in isolated microperfused rabbit afferent arterioles via endothelium-derived nitric oxide.

Flow may be a physiological stimulus of the endothelial release of nitric oxide (NO) and prostaglandins (PGs). We tested the hypothesis that pressure-induced constriction of the glomerular afferent arteriole (Af-Art) is modulated by luminal flow via endothelial production of NO. We microdissected the terminal segment of an interlobular artery together with two Af-Arts, their glomeruli (GL) and efferent arterioles (Ef-Art). The two Af-Arts were perfused simultaneously from the interlobular artery, while one Ef-Art was occluded. Since the arteriolar perfusate contained 5% albumin, oncotic pressure built up in the glomerulus with the occluded Ef-Art and opposed the force of filtration, resulting in little or no flow through the corresponding Af-Art. Thus this preparation allowed us to observe free-flow and no-flow Af-Arts simultaneously during stepwise 30-mmHg increases in intraluminal pressure (from 30 to 120 mmHg). Pressure-induced constriction was weaker in free-flow than no-flow Af-Arts, with the luminal diameter decreasing by 11.1 +/- 1.7 and 25.6 +/- 2.3% (n = 30), respectively, at 120 mmHg. To examine whether flow modulates myogenic constriction through endothelium-derived NO and/or PGs, we examined pressure-induced constriction before and after (a) disruption of the endothelium, (b) inhibition of NO synthesis with NW-nitro-L-arginine methyl ester (L-NAME), or (c) inhibition of cyclooxygenase with indomethacin. Both endothelial disruption and L-NAME augmented pressure-induced constriction in free-flow but not no-flow Af-Arts, abolishing the differences between the two. However, indomethacin had no effect in either free-flow or no-flow Af-Arts. These results suggest that intraluminal flow attenuates pressure-induced constriction in Af-Arts via endothelium-derived NO. Thus flow-stimulated NO release may be important in the fine control of glomerular hemodynamics.

Endothelium-derived relaxing factor inhibits transport and increases cGMP content in cultured mouse cortical collecting duct cells.

Stimulation of the release of endothelium-derived relaxing factor (EDRF) in the kidney has been shown to result in natriuresis without affecting glomerular filtration rate. This may be due to EDRF directly regulating solute transport in the cortical collecting duct (CCD). To test this hypothesis, we measured the effect of bradykinin (Bk) or acetylcholine (Ach) on short-circuit current (Isc; a measure of active transport) in a CCD cell line (M-1), in the presence or absence of cow pulmonary artery endothelial (CPAE) cells. 10(-9) M Bk or 10(-7) M Ach had no effect on M-1 Isc in which CPAE cells were absent. The addition of CPAE cells to M-1 cells also did not affect M-1 Isc. On the other hand, when 10(-9) M Bk or 10(-7) M Ach were added to M-1 cells in the presence of CPAE cells, Isc decreased from 43 +/- 4.5 to 26 +/- 4 and 64 +/- 9 to 33 +/- 4 microA/cm2, respectively (P less than 0.001). Nitroarginine (N-Arg, 10(-4) M), a competitive inhibitor of EDRF production, blocked the inhibition in M-1 Isc due to both agonists. Since cGMP is the second messenger of EDRF in vascular smooth muscle, we measured the effects of Bk on cGMP production in M-1 cells in the presence and absence of CPAE cells. Bk increased cGMP content in M-1 cells in the presence of CPAE cells from 33 +/- 3.4 to 132 +/- 11.7 fmol/10(6) M-1 cells (P less than 0.001). When cultures of M-1 and CPAE cells were treated with N-Arg and challenged with Bk, Bk's effect on cGMP was partially blocked (61.4 +/- 12 fmol/10(-6) M-1 cells; NS). These data suggest that EDRF inhibits transport and increases cGMP content in M-1 cells.

Effects of angiotensin-converting enzyme inhibitors and angiotensin II type 1 receptor antagonists in rats with heart failure. Role of kinins and angiotensin II type 2 receptors.

Angiotensin-converting enzyme inhibitors (ACEi) improve cardiac function and remodeling and prolong survival in patients with heart failure (HF). Blockade of the renin-angiotensin system (RAS) with an angiotensin II type 1 receptor antagonist (AT1-ant) may have a similar beneficial effect. In addition to inhibition of the RAS, ACEi may also act by inhibiting kinin destruction, whereas AT1-ant may block the RAS at the level of the AT1 receptor and activate the angiotensin II type 2 (AT2) receptor. Using a model of HF induced by myocardial infarction (MI) in rats, we studied the role of kinins in the cardioprotective effect of ACEi. We also investigated whether an AT1-ant has a similar effect and whether these effects are partly due to activation of the AT2 receptor. Two months after MI, rats were treated for 2 mo with: (a) vehicle; (b) the ACEi ramipril, with and without the B2 receptor antagonist icatibant (B2-ant); or (c) an AT1-ant with and without an AT2-antagonist (AT2-ant) or B2-ant. Vehicle-treated rats had a significant increase in left ventricular end-diastolic (LVEDV) and end-systolic volume (LVESV) as well as interstitial collagen deposition and cardiomyocyte size, whereas ejection fraction was decreased. Left ventricular remodeling and cardiac function were improved by the ACEi and AT1-ant. The B2-ant blocked most of the cardioprotective effect of the ACEi, whereas the effect of the AT1-ant was blocked by the AT2-ant. The decreases in LVEDV and LVESV caused by the AT1-ant were also partially blocked by the B2-ant. We concluded that (a) in HF both ACEi and AT1-ant have a cardioprotective effect, which could be due to either a direct action on the heart or secondary to altered hemodynamics, or both; and (b) the effect of the ACEi is mediated in part by kinins, whereas that of the AT1-ant is triggered by activation of the AT2 receptor and is also mediated in part by kinins. We speculate that in HF, blockade of AT1 receptors increases both renin and angiotensins; these angiotensins stimulate the AT2 receptor, which in turn may play an important role in the therapeutic effect of the AT1-ant via kinins and other autacoids.

Diminished cardioprotective response to inhibition of angiotensin-converting enzyme and angiotensin II type 1 receptor in B(2) kinin receptor gene knockout mice.

Using B(2) kinin receptor gene knockout mice (B(2)(-/-)), we tested the hypothesis that (l) lack of B(2) receptors may affect blood pressure and cardiac function and aggravate cardiac remodeling after myocardial infarction (MI), and (2) kinins partially mediate the cardiac beneficial effect of angiotensin-converting enzyme inhibitors (ACEi) or angiotensin II type 1 receptor antagonists (AT(1)-ant), whereas lack of B(2) receptors may diminish this cardioprotective effect. Chronic heart failure (HF) was induced by MI, which was caused by coronary artery ligation in both B(2)(-/-) and 129/SvEvTac mice (wild-type control, B(2)(+/+)). An ACEi (ramipril, 2.5 mg/kg/d) or AT(1)-ant (L-158809, 3 mg/kg/d) was given 1 week after MI and was continued for 12 weeks. Left ventricular (LV) ejection fraction, cardiac output (CO), diastolic LV dimension (LVDd), and LV mass were evaluated by echocardiography. Myocyte cross-sectional area and interstitial collagen fraction were studied histopathologically. We found that basal blood pressure and cardiac function were similar in B(2)(+/+) and B(2)(-/-) mice. After MI, development of HF and remodeling were also similar between the 2 strains. The ACEi improved cardiac function and remodeling in both strains; however, its effects were attenuated in B(2)(-/-) mice (respective values for B(2)(+/+) versus B(2)(-/-) mice: overall increase in ejection fraction, 64+/-10% versus 21+/-5% [P<0.01]; increase in CO, 69+/-17% versus 23+/-9% [P<0.01]; overall decrease in LVDd, -24+/-3% versus -7+/-4% [P<0.01]; and decrease in LV mass, -38+/-3% versus -6+/-6% [P<0.01]). AT(1)-ant had a beneficial cardiac effect similar to that produced by ACEi, and this effect was also diminished in B(2)(-/-) mice (respective values for B(2)(+/+) versus B(2)(-/-) mice: overall increase in ejection fraction, 46+/-10% versus 25+/-9% [P<0.01]; increase in CO, 44+/-14% versus 15+/-5% [P<0.01]; overall decrease in LVDd, -14+/-4% versus -6+/-3% [P<0.01]; and decrease in LV mass, -33+/-4 versus -16+/-7% [P<0.01]). The effect of ACEi or AT(1)-ant on myocyte cross-sectional area was similar between strains; however, their effect on the interstitial collagen fraction was diminished in B(2)(-/-) mice. We concluded that (1) lack of B(2) kinin receptors does not affect cardiac phenotype or function, either under normal physiological conditions or during the development of HF; and (2) kinins acting via the B(2) receptor play an important role in the cardioprotective effect of ACEi and AT(1)-ant.

Tissue kallikrein processes small proenkephalin peptides.

Tissue kallikrein may play a role in processing precursor polypeptide hormones. We investigated whether hydrolysis of natural enkephalin precursors, peptide F and bovine adrenal medulla docosapeptide (BAM-22P), by hog pancreatic kallikrein is consistent with this concept. Incubation of peptide F with this tissue kallikrein resulted in the release of Met5-enkephalin and Met5-Lys6-enkephalin. Met5-Lys6-enkephalin was the main peptide released, indicating that the major cleavage site was between two lysine residues. At 37 degrees C and pH 8.5, the KM values for formation of Met5-enkephalin and Met5-Lys6-enkephalin were 129 and 191 microM, respectively. Corresponding kcat values were 0.001 and 0.03 s-1 and kcat/KM ratios were 8 and 1.6.10(2) M-1.s-1, respectively. Cleavage of peptide F at acidic pH (5.5) was negligible. When BAM-22P was used as a substrate, Met5-Arg6-enkephalin was released, thus indicating cleavage between two arginine residues. At pH 8.5, KM was 64 microM, kcat was 4.5 s-1, and the kcat/KM ratio was 7.10(4) M-1.s-1. At 5.5, the pH of the secretory granules, KM, kcat and kcat/KM were 184 microM, 1.9 s-1 and 10(4) M-1.s-1, respectively. It is unlikely that peptide F could be a substrate for kallikrein in vivo; however, tissue kallikrein could aid in processing proenkephalin precursors such as BAM-22P by cleaving Arg-Arg peptide bonds.

Oxidation of 5,8,11,14,17-eicosapentaenoic acid by hepatic and renal microsomes.

Liver and kidney microsomes were isolated from rats raised on high-fat diets. In terms of energy, the high-fat diets contained 4% vegetable and 40% fish, vegetable or coconut oils. Each microsomal preparation was fortified with 1 mM NADPH and incubated with 5,8,11,14,17-eicosapentaenoic acid (20:5(n-3]. The number of metabolites formed was assessed by reverse-phase high-performance liquid chromatography (HPLC). To identify the major metabolites, large-scale incubations were done with 20:5(n-3) and microsomes from phenobarbital-treated rats. After extracts from the phenobarbital and dietary studies were combined, individual products were isolated by reverse- and normal-phase HPLC. The metabolites were identified by mass spectrometry, by chromatographic properties, and by comparing their retention times and mass spectra with those of chemically synthesized standards. For liver microsomes, the major metabolites were: 17,18-, 14,15-, 11,12- and 8,9-dihydroxyeicosatetraenoic acids, 20-hydroxyeicosapentaenoic acid, and 19-hydroxyeicosatetraenoic acid. For renal microsomes, the major metabolites were 20-hydroxyeicosapentaenoic and 19-hydroxypentaenoic acids. Because formation of these metabolites required NADPH and was enhanced by phenobarbital pretreatment, 20:5(n-3) appears to be oxidized by cytochrome P-450 monooxygenases. Based on reverse-phase high performance liquid chromatograms, all three high-fat diets may produce the same types of monooxygenase metabolites from 20:5(n-3). It remains unknown whether fish-oil diets induce the synthesis of monooxygenases to oxidize n-3 fatty acids, because these preliminary studies involved only two animals per dietary group.

Long-term effect of N-acetyl-seryl-aspartyl-lysyl-proline on left ventricular collagen deposition in rats with 2-kidney, 1-clip hypertension.

BACKGROUND: N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a natural inhibitor of pluripotent hematopoietic stem cell proliferation. Ac-SDKP plasma concentration is increased 5-fold after angiotensin-converting enzyme inhibition. Here we studied the effect of Ac-SDKP on monocyte/macrophage infiltration, fibroblast proliferation, and collagen deposition in the rat heart in renovascular hypertension. METHODS AND RESULTS: We investigated whether long-term Ac-SDKP administration would prevent left ventricular (LV) hypertrophy and interstitial collagen deposition in rats with 2-kidney, 1-clip (2K-1C) hypertension. Ac-SDKP (400 microgram. kg(-1). d(-1)) did not affect development of hypertension. Mean blood pressure was similar in rats with 2K-1C hypertension whether they were given vehicle or Ac-SDKP and was higher than in controls. Both LV weight and cardiomyocyte size were significantly increased in rats with 2K-1C hypertension compared with controls and were unaffected by Ac-SDKP. Proliferating cell nuclear antigen- and monocyte/macrophage-positive cells were increased in the LV of 2K-1C hypertensive rats; this increase was significantly blunted by Ac-SDKP (P<0.001). LV interstitial collagen fraction was also increased in 2K-1C hypertensive rats given vehicle (10.1+/-0.8%) compared with sham (5.3+/-0.1%, P<0.0001), and this increase was prevented by Ac-SDKP (5.4+/-0.4%, P<0.001). CONCLUSIONS: Ac-SDKP inhibited monocyte/macrophage infiltration, cell proliferation, and collagen deposition in the LV of hypertensive rats without affecting blood pressure or cardiac hypertrophy, suggesting that it may be partly responsible for the cardioprotective effect of angiotensin-converting enzyme inhibitors.

Ren1d and Ren2 cooperate to preserve homeostasis: evidence from mice expressing GFP in place of Ren1d.

To distinguish the contributions of Ren1(d) and Ren2 to kidney development and blood pressure homeostasis, we placed green fluorescent protein (GFP) under control of the Ren1(d) renin locus by homologous recombination in mice. Homozygous Ren1(d)-GFP animals make GFP mRNA in place of Ren1(d) mRNA in the kidney and maintain Ren2 synthesis in the juxtaglomerular (JG) cells. GFP expression provides an accurate marker of Ren1(d) expression during development. Kidneys from homozygous animals are histologically normal, although with fewer secretory granules in the JG cells. Blood pressure and circulating renin are reduced in Ren1(d)-GFP homozygotes. Acute administration of losartan decreases blood pressure further, suggesting a role for Ren2 protein in blood pressure homeostasis. These studies demonstrate that, in the absence of Ren1(d), Ren2 preserves normal kidney development and prevents severe hypotension. Chronic losartan treatment results in compensation via recruitment of both Ren1(d)- and Ren2-expressing cells along the preglomerular vessels. This response is achieved by metaplastic transformation of arteriolar smooth muscle cells, a major mechanism to control renin bioavailability and blood pressure homeostasis.

Neither endogenous nor exogenous bradykinin stimulates aldosterone in vivo.

It has been suggested that bradykinin (BK) can directly stimulate aldosterone secretion in vitro. Both chronic and acute studies were performed to determine whether we could show a pathway by which BK could stimulate plasma aldosterone in vivo. Chronic studies employed four groups of eight rats fed either a normal sodium or a sodium-restricted diet over 9 days. Half of the rats received infusion of a saline vehicle, and the others received the BK B-2 receptor antagonist HOE-140 at a rate of 200 micrograms/kg.day over 7 days via a sc implanted osmotic minipump. This rate was derived from studies showing that HOE-140 blocked pharmacological doses of exogenous BK. With a normal diet, there was no difference in plasma aldosterone in vehicle-treated rats vs. those treated with HOE-140 (368 +/- 55 vs. 329 +/- 66 pg/ml, respectively). Sodium restriction increased plasma aldosterone 10-fold, but again there was no difference between vehicle-treated rats and those treated with HOE-140 (2964 +/- 439 vs. 3755 +/- 475 pg/ml, respectively). Acute studies employed two groups of six rats. Direct suprarenal intraaortic infusion of 2 micrograms/min BK or saline vehicle was performed over 2 h. Plasma aldosterone was not changed in vehicle-treated groups, but decreased by 22% (P < 0.05) after BK infusion. Thus, blockade of kinin B-2 receptors had no effect on plasma aldosterone in normal or sodium-restricted diet rats. Acute BK infusion did not increase plasma aldosterone. We conclude that although BK may stimulate aldosterone in vitro, we found no physiological correlate to suggest that BK regulates plasma aldosterone in vivo.

Local hormonal factors (intracrine, autocrine, and paracrine) in hypertension.

Vasoactive hormones acting as endocrine, neuroendocrine, or local hormonal systems (intracrine, autocrine, and paracrine) are an important component of the many factors that regulate blood pressure. Hypertension may be the result of an alteration in the balance between vasodepressor and vasopressor hormonal systems. Changes in this balance could be due to genetic factors such as mutations in one of the genes of the vasoactive system or environmental factors that alter the synthesis and release of one or more vasoactive hormones. Endocrine and neuroendocrine vasopressor hormonal systems, such as the renin-angiotensin system and catecholamines, play a well-established and important role in the regulation of blood pressure and the pathogenesis of some secondary forms of hypertension. The blockade of such systems has already resulted in effective antihypertensive treatment. The role of local hormonal systems is less well established; however, recent evidence suggests they also play an important role in the regulation of blood pressure and the pathogenesis of hypertension. Some vasopressor hormonal systems, such as the renin-angiotensin system, can act as both endocrine or local hormonal systems. Work using transgenic rats harboring the mouse Ren-2 gene has conclusively demonstrated that the renin-angiotensin system, acting as a local hormonal system, has the capability to cause severe hypertension. Whether this model of experimental hypertension mimics any type of human hypertension is not known. Vasodepressor hormones such as kinins, prostaglandins, and endothelium-derived relaxing factor (EDRF) act mainly as local hormonal systems, with the notable exception of atrial natriuretic factor, which may act as both an endocrine and a local hormone. The tissue kallikrein-kinin system, acting either directly or via paracrine eicosanoids or EDRF, participates in local regulation of the circulation, renal function, and the acute antihypertensive effect of angiotensin converting enzyme inhibitors. A restriction fragment length polymorphism (RFLP) that distinguishes the kallikrein gene family of a strain of spontaneously hypertensive rats (SHR) from normotensive Brown Norway rats has been identified. In a set of 32 recombinant inbred strains derived from these SHR and Brown Norway strains, the RFLP marking the kallikrein gene family of SHR cosegregated with an increase in blood pressure. Also, in a study of Utah families it was found that a dominant-allele kallikrein gene expressed as high urinary kallikrein excretion was associated with a decreased risk of essential hypertension. In conclusion, vasopressor and vasodepressor hormones, acting not only as endocrine but also as local hormones, play an important role in the regulation of blood pressure and the pathogenesis of hypertension.(ABSTRACT TRUNCATED AT 400 WORDS)

Kinin antagonist reverses converting enzyme inhibitor-stimulated vascular prostaglandin I2 synthesis.

Treatment with a converting enzyme inhibitor has been shown to stimulate aortic prostaglandin I2 synthesis. We studied whether converting enzyme inhibitor-stimulated prostaglandin I2 synthesis might be mediated by kinins. Anesthetized male Sprague-Dawley rats were given a continuous 70-minute infusion of either saline or a kinin analogue antagonist, [DArg0-Hyp3-Thi5-DPhe7-Thi8]bradykinin, 8 micrograms/kg/min. After 10 minutes, rats were given an intravenous bolus of either vehicle or the converting enzyme inhibitor enalaprilat (30 micrograms/100 g body wt). After 70 minutes, aorta and renal cortical slices were harvested and incubated in vitro in buffer without drugs at pH 7.4, 37 degrees C for 60 minutes. The buffer was then sampled for measurement of 6-keto prostaglandin F1 alpha (an index of prostaglandin I2), prostaglandin E2, and renin release (angiotensin I generation) by radioimmunoassay. The aortic prostaglandin I2 from rats treated with converting enzyme inhibitor was significantly elevated (36.7 +/- 5.0 ng/mg dry wt/hr) compared with aorta from rats treated with either vehicle (25.6 +/- 2.2 ng/mg/hr), kinin antagonist (25.1 +/- 2.4 ng/mg/hr), or kinin antagonist plus converting enzyme inhibitor (23.0 +/- 2.0 ng/mg/hr), p less than 0.02. There were no differences in aortic prostaglandin E2, renin release, or prostaglandin E2 from renal cortical slices. Direct in vitro incubation of aorta with molar concentrations of converting enzyme inhibitor from 10(-9) to 10(-4) had no effect on prostaglandin I2. These results suggest that kinins may mediate the effect of converting enzyme inhibition on aortic prostaglandin I2 synthesis and thereby may account for part of the hemodynamic responses resulting from treatment using converting enzyme inhibitors.