Biomedical subjects

H K Jin

Publications and source records attributed to H K Jin.

At least 19 recordsLinked to original sources

PubMed2001

Suppression by a sesquiterpene lactone from Carpesium divaricatum of inducible nitric oxide synthase by inhibiting nuclear factor-kappaB activation.

Excessive nitric oxide (NO) produced by inducible NO synthase (iNOS) acts as a causative regulator in various inflammatory disease states. Carpesium divaricatum has been used in Korean traditional herbal medicine for its antipyretic, analgesic, vermifugic, and anti-inflammatory properties. We investigated the molecular mechanism for the suppression of lipopolysaccharide/interferon-gamma (LPS/IFN-gamma)-induced NO production in RAW 264.7 macrophages by the sesquiterpene lactone 2beta,5-epoxy-5,10-dihydroxy-6alpha-angeloyloxy-9beta-isobutyloxy-germacran-8alpha,12-olide (C-1), which has been identified recently as a new compound from C. divaricatum. C-1 decreased NO production in LPS/IFN-gamma-stimulated RAW 264.7 cells in a concentration-dependent manner, with an IC50 of approximately 2.16 microM; however, it had no direct effect on the iNOS activity of fully LPS/IFN-gamma-stimulated RAW 264.7 cells. Furthermore, treatment with C-1 led to a decrease in iNOS protein and mRNA. These effects appear to be due to inhibition of nuclear factor-kappaB (NF-kappaB) activation through a mechanism involving stabilization of the NF-kappaB/inhibitor of the kappaB (I-kappaB) complex, since inhibition of NF-kappaB DNA binding activity by C-1 was accompanied by a parallel reduction of nuclear translocation of subunit p65 of NF-kappaB and I-kappaBalpha degradation. Taken together, the results suggest that the ability of C-1 to inhibit iNOS gene expression may be responsible, in part, for its anti-inflammatory effects.

Animals↗

PubMed2001

Mouse Mx2 protein inhibits hantavirus but not influenza virus replication.

The antiviral potential of Mx2 protein remains unknown, because the Mx2 gene in commonly used strains of laboratory mice is nonfunctional. Our previous study showed that functional Mx2 protein in some feral-origin strains was induced upon interferon treatment, was localized in the cytoplasm, and inhibited vesicular stomatitis virus replication. In the present study, we have demonstrated that the embryonic fibroblastic cells from a feral-origin strain (SPR) expressed 74 kDa Mx2 protein, which prevented the accumulation of viral transcripts and proteins of hantaviruses when the Mx2 gene was constitutively expressed in transfected Vero cells. Furthermore, the cells showed significantly lower titers of the virus than control cells. In contrast, influenza virus replication was not affected by the expression of Mx2 protein in the Vero cells.

Animals↗

PubMed2001

The roles of Nramp1 and Tnfa genes in nitric oxide production and their effect on the growth of Salmonella typhimurium in macrophages from Nramp1 congenic and tumor necrosis factor-alpha-/- mice.

The macrophages from Nramp1 congenic mice and tumor necrosis factor (TNF)-alpha(-/-) mice were used to examine the functions of Nramp1 and Tnfa genes in nitric oxide (NO) production and Salmonella typhimurium infection. It was confirmed that the level of inducible NO synthase (iNOS)-mediated NO production in Nramp1(r) peritoneal macrophages was generally higher than that of Nramp1(s) macrophages after stimulation by interferon-gamma (IFN-gamma), lipopolysaccharide (LPS), and tumor necrosis factor-alpha (TNF-alpha) alone or in combination. Nramp1 mRNA expression in both Nramp1 congenic macrophages was constitutive notwithstanding cytokine stimulation. During infection with S. typhimurium strain 6203, Nramp1(r) macrophages produced a lower amount of NO because of an initial strong reaction and unsustained iNOS gene expression as compared with Nramp1(s) macrophages. An inhibitory effect of the Nramp1(r) gene on bacterial replication was also observed during the early stage of S. typhimurium infection, whereas the effect of TNF-alpha occurred later. NO production and iNOS expression in TNF-alpha(-/-) macrophages were not detected from the start of the bacterial infection or at 24 h after infection. We also observed that S. typhimurium strain 6203 grew more profoundly without TNF-alpha, especially in Nramp1(s) macrophages. These data, therefore, demonstrate that there is cooperation of the Nramp1 and Tnfa genes in NO production and a growth inhibitory effect in response to S. typhimurium infection.

Animals↗

PubMed2001

Vascular endothelial growth factor-mediated endothelium-dependent relaxation is blunted in spontaneously hypertensive rats.

The vasodilatory effect of VEGF has not been characterized in the setting of hypertension. This study investigated the in vitro vasorelaxant effects of VEGF in organ chambers in the aorta of the adult (12-week-old) spontaneously hypertensive rats (SHR), young (4-week-old) SHR without hypertension, and age-matched Wistar-Kyoto (WKY) rats compared with acetylcholine (ACh). Cumulative concentration-relaxation curves were established for VEGF (approximately 10(-12)-10(-8.5) M) and ACh (approximately 10(-10)-10(-5) M) in U46619 (10(-8) M)-induced contraction. VEGF induced endothelium-dependent relaxation that was significantly reduced in the adult SHR compared with the age-matched WKY control (87.8 +/- 2.8 versus 61.4 +/- 8.6%, P = 0.01). These responses were significantly attenuated by pretreatment with N(omega)-nitro-L-arginine (L-NNA, 300 microM) alone (SHR: 25.1 +/- 1.9%; WKY: 21.0 +/- 2.6%; P = 0.01) or indomethacin (7 microM) + L-NNA (SHR: 30.2 +/- 2.1%; WKY: 35.0 +/- 2.9%; P = 0.01). Further addition of oxyhemoglobin (20 microM) abolished the residual relaxation and reduced the relaxation induced by nitroglycerin. ACh induced similar responses to VEGF. In contrast, pretreatment with indomethacin alone enhanced VEGF- or ACh-induced relaxations and the effect was greater in the adult SHR than in WKY rats. In contrast to the adult SHR versus WKY rats, there were no significant differences of VEGF- or ACh-induced relaxations between young SHR and WKY rats. The results demonstrate that VEGF induces endothelium- or nitric oxide-dependent relaxation, which is blunted in the adult SHR. The mechanism of this impairment may be related to decreased release of NO although increased release of contracting factors from the dysfunctional endothelium may also be involved.

Acetylcholine↗

PubMed1999

Jumbled spine and ribs (Jsr): a new mutation on mouse chromosome 5.

Jumbled spine and ribs (Jsr) is an autosomal dominant mutation that results in malformation of the axial skeleton. The vertebrae of mutant mice (Jsr/+) are all shorter than those of normal mice (+/+) in the inbred line and show various abnormalities. In addition, several ribs are fused at their proximal region because of fusion of thoracic vertebrae. In this study, we localized the Jsr mutation on distal Chromosome (Chr) 5 and constructed a high-resolution map. Chromosomal mapping was performed with an inter-subspecific backcross of (CKH-Jsr/+ x MOG) F1 carrying the Jsr allele and CKH-+/+. The predicted gene order around Jsr was determined to be cen-(Epo, Pdgfa, D5Mit31, D5Mit374)-(Jsr, Nfe2u, D5Mit99, D5Mit247, D5Mit284, D5Mit292, D5Mit327)-D5Mit328-tel. Subsequently, high-resolution mapping concluded the Jsr localization to be cen-Nfe2u-1.0cM-Jsr-0.2cM-D5Mit247,292-tel . Jsr/Jsr homozygotes are alive, as the mutation is not lethal. Based on histological analysis of mutant embryos, Jsr is hypothesized to be caused by abnormal development of primordial cells in the axial skeleton.

Animals↗

PubMed1999

Identification of the murine Mx2 gene: interferon-induced expression of the Mx2 protein from the feral mouse gene confers resistance to vesicular stomatitis virus.

The mouse genome contains two related interferon-regulated genes, Mx1 and Mx2. Whereas Mx1 codes for the nuclear 72-kDa protein that interferes with influenza virus replication after interferon treatment, the Mx2 gene is nonfunctional in all laboratory mouse strains examined, since its open reading frame (ORF) is interrupted by an insertional mutation and a subsequent frameshift mutation. In the present study, we demonstrate that Mx2 mRNA of cells from feral mouse strains NJL (Mus musculus musculus) and SPR (Mus spretus) differs from that of the laboratory mouse strains tested. The Mx2 mRNA of the feral strains contains a single long ORF consisting of 656 amino acids. We further show that Mx2 protein in the feral strains is expressed upon interferon treatment and localizes to the cytoplasm much like the rat Mx2 protein, which inhibits vesicular stomatitis virus replication. Furthermore, transfected 3T3 cell lines of laboratory mouse origin expressing Mx2 from feral strains acquire slight resistance to vesicular stomatitis virus.

Amino Acid Sequence↗

PubMed1998

Characterization and expression of the Mx1 gene in wild mouse species.

The mouse Mx1 gene encodes an interferon (IFN)-inducible nuclear protein and confers resistance to influenza virus infection. The standard laboratory mouse strains all carry the Mx1- allele and are susceptible to influenza virus. In this study, several mouse strains established from wild mice were tested to determine their Mx1+ or Mx1- allele status with polymerase chain reaction-restriction fragment length variation (PCR-RFLV), sequence analysis, reverse transcription (RT)-PCR, and immunofluorescence staining. All of the mouse strains originating from wild mice were found uniformly to carry the Mx1+ allele. Therefore, it is conceivable that the Mx1+ allele in wild populations serves a function against some pathogens related to orthomyxoviruses. The PCR-RFLV and sequence analysis allowed us to classify the Mx1+ alleles of the laboratory and wild-origin mouse strains into distinct classes. RT-PCR and immunofluorescence staining demonstrated that the Mx1 transcripts and proteins were induced by IFN-alpha/beta in macrophages from wild mouse species.

Animals↗

PubMed1992

Pressor effect of blocking atrial natriuretic peptide in nucleus tractus solitarii.

Previous studies have shown that microinjection of atrial natriuretic peptide into the caudal nucleus tractus solitarii produces significant increases in local neuronal firing rate associated with reductions in arterial pressure in anesthetized Wistar rats. Single units excited by microinjection of atrial natriuretic peptide into the caudal nucleus tractus solitarii were also excited by activation of arterial baroreceptors and inhibited by baroreceptor unloading. To test the hypothesis that endogenous atrial natriuretic peptide in caudal nucleus tractus solitarii is involved in the tonic control of blood pressure in the rat, we administered a blocking monoclonal antibody to atrial natriuretic peptide in a volume of 50 nl artificial cerebrospinal fluid via microinjection into the caudal nucleus tractus solitarii of spontaneously hypertensive and Wistar-Kyoto rats and observed the effects on mean arterial pressure and heart rate. Control injections of monoclonal antibody were administered into the rostral nucleus tractus solitarii, hypoglossal nucleus, spinal trigeminal nucleus, and cuneate nucleus of spontaneously hypertensive rats. Microinjection of monoclonal antibody into the caudal nucleus tractus solitarii caused significant increases in mean arterial pressure in spontaneously hypertensive rats but not in Wistar-Kyoto rats. There was no concomitant change in heart rate. Control injections of purified mouse immunoglobulin into the caudal nucleus tractus solitarii and of monoclonal antibody into the control neuronal groups listed above had no effect on mean arterial pressure. These results suggest that endogenous atrial natriuretic peptide in the caudal nucleus tractus solitarii mediates tonic control of blood pressure in spontaneously hypertensive rats but not in normotensive Wistar-Kyoto rats.

Animals↗

PubMed1991

Dietary Ca2+ prevents NaCl-sensitive hypertension in spontaneously hypertensive rats via sympatholytic and renal effects.

NaCl-sensitive spontaneously hypertensive rats (SHR-S) were used to test the hypotheses that dietary Ca2+ supplementation 1) prevents NaCl-sensitive hypertension via a sympatholytic mechanism, and 2) increases diuretic and natriuretic responses to acute volume loading. SHR-S and control WKY rats were begun on one of four diets at age 8 wk: control, high NaCl, high Ca2+, or high NaCl and high Ca2+. In SHR-S, dietary Ca2+ supplementation prevented the NaCl-induced increases in blood pressure and plasma norepinephrine concentrations, the reductions in anterior hypothalamic norepinephrine stores and turnover, and the secondary increases in alpha 2 adrenoceptor number. Thus, Ca2+ prevented NaCl-sensitive hypertension in SHR-S by increasing noradrenergic input to the anterior hypothalamus. High-NaCl-fed SHR-S had impaired diuretic and natriuretic responses to an isotonic volume load; Ca2+ enhanced the ability of these animals to adjust fluid volume rapidly via diuresis and natriuresis. This alteration in renal function may contribute to the hypotensive effect of a high Ca2+ diet in NaCl-sensitive hypertension.

Animals↗

PubMed1991

Altered stores of atrial natriuretic peptide in specific brain nuclei of NaCl-sensitive spontaneously hypertensive rats.

Previous studies from our laboratories have demonstrated a selective increase in stores of atrial natriuretic peptide (ANP) in the anterior hypothalamus of NaCl-sensitive spontaneously hypertensive rats (SHR-S) compared to NaCl-resistant Wistar-Kyoto (WKY) controls and have suggested that anterior hypothalamic ANP contributes to the pathogenesis of NaCl-sensitive hypertension in SHR-S by local inhibition of norepinephrine release. We have also observed blunting of cardiopulmonary and arterial baroreflex function in SHR-S compared to WKY. In the current study, ANP stores in 12 brain nuclei thought to participate in the pathogenesis of hypertension, including locus coeruleus (LC), A1/C1 area (A1/C1), nucleus tractus solitarii (NTS), medial preoptic nucleus (MPON), suprachiasmatic nucleus (SCN), supraoptic nucleus (SON), anterior hypothalamic area (AHA), paraventricular hypothalamic nucleus (PVN), ventromedial hypothalamic nucleus (VMN), dorsomedial hypothalamic nucleus (DMN), lateral hypothalamic nucleus (LN), and posterior hypothalamic area (PHA), were compared in 10-week-old male SHR-S and WKY rats following 3 weeks of 1% v 8% NaCl feeding. Individual brain nuclei were obtained by the micropunch technique and ANP content of bilateral brain nuclei from individual rats was measured by radioimmunoassay. ANP content was significantly decreased in NTS and LC and elevated in AHA of SHR-S compared to WKY rats on either diet. Dietary NaCl supplementation was associated with increased ANP content in PVN of both strains. These alterations in ANP content in SHR-S may be related to the reduced release of norepinephrine from nerve terminals in AHA and to the presumed central defect in baroreceptor function.

Analysis of Variance↗

PubMed1991

Antihypertensive effect of cicletanine is exaggerated in NaCl-sensitive hypertension.

Cicletanine (CIC), a furopyridine derivative, lowers blood pressure in hypertensive animals and humans. We have previously identified an NaCl-sensitive substrain of spontaneously hypertensive rat (SHR-S) that displays enhanced sensitivity to the depressor effects of exogenous atrial natriuretic peptide (ANP) when fed a high NaCl diet. The current study tested the hypotheses that CIC has an exaggerated antihypertensive effect in NaCl-supplemented SHR-S and that this effect might be ANP dependent. CIC (40 mg/kg/day) or vehicle was administered by gavage in a single daily dose for three weeks beginning immediately prior to initiation of 1% or 8% NaCl diets in seven-week-old male SHR-S. CIC significantly decreased mean arterial pressure (MAP) and the ratio of left ventricular and septum weight to body weight (LV + S/BW) in both 8% NaCl- and 1% NaCl-fed SHR-S. The depressor effect of CIC was greater in the 8% NaCl group (-26 mmHg) than in the 1% NaCl group (-13 mmHg). CIC was associated with significant reduction in RAP in the 8% NaCl group but not in the 1% NaCl group. Neither CIC treatment nor 8% NaCl significantly altered plasma ANP or cyclic guanosine monophosphate (GMP) levels in plasma, aorta, or kidney. CIC was associated with significant decreases in plasma norepinephrine (NE) levels in the 1% NaCl group but not in the 8% NaCl group. The data demonstrate that the antihypertensive effect of CIC is exaggerated in NaCl-sensitive hypertension. The antihypertensive effect of CIC appears not to be related to ANP or cyclic GMP but may be related to a combination of a sympatholytic and natriuretic/diuretic effects in SHR-S.

Animals↗

PubMed1991

Intrahypothalamic clonidine infusion prevents NaCl-sensitive hypertension.

We have previously shown that dietary NaCl supplementation increases blood pressure and sympathetic nervous system activity in association with decreased norepinephrine release and increased alpha 2-adrenergic receptor number in the anterior hypothalamic area of salt-sensitive spontaneously hypertensive rats (SHR-S) but not in salt-resistant spontaneously hypertensive rats (SHR-R) or Wistar-Kyoto (WKY) rats. Further, acute microinjection of clonidine into the anterior hypothalamic area produced depressor responses that were augmented by high salt feeding in SHR-S but not in SHR-R or WKY rats. The current study tested the hypothesis that chronic infusion of clonidine into the anterior hypothalamic area prevents salt-sensitive hypertension in SHR-S. Beginning at age 7 weeks, immediately before initiation of 1% or 8% salt diets, clonidine (2 ng/min) or saline vehicle was infused into the anterior hypothalamic area or femoral vein of male SHR-S via osmotic minipump for 20 days. In SHR-S fed an 8% salt diet, chronic microinfusion of clonidine into the anterior hypothalamic area offset the hypertensive effect of the dietary salt supplementation and reduced the enhancing effects of dietary salt on left ventricular weight and plasma norepinephrine levels. In contrast, chronic microinfusion of clonidine into the anterior hypothalamic area did not significantly affect any of these measures in 1% salt-fed SHR-S. Intravenous infusion of clonidine at the rate used for the anterior hypothalamic area infusion did not alter any of these measures in 8% salt-fed SHR-S.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1990

Dietary Ca2+ prevents NaCl-sensitive hypertension in spontaneously hypertensive rats by a sympatholytic mechanism.

The current study tested the hypothesis that dietary Ca2+ supplementation reverses the NaCl-sensitive component of hypertension and the associated neurochemical abnormalities in the NaCl-sensitive spontaneously hypertensive rat (SHR-S). Male SHR-S were begun on one of four diets at 8 weeks of age: control (0.75% NaCl/0.68% Ca2+); high NaCl (8.00% NaCl/0.68% Ca2+); high Ca2+ (0.75% NaCl/2.00% Ca2+); and high NaCl/high Ca2+ (8.00% NaCl/2.00% Ca2+). High NaCl SHR-S (X2 weeks) had higher mean arterial pressure (MAP) (161 +/- 4 mm Hg) than controls (149 +/- 3 mm Hg; P less than .05). Supplementation with Ca2+ prevented the rise in MAP in high NaCl rats, but did not alter MAP in controls. The 8% NaCl diet elevated plasma norepinephrine and reduced anterior hypothalamic (AHA) norepinephrine stores and turnover; concomitant Ca2+ supplementation restored both plasma norepinephrine and AHA norepinephrine turnover to normal. Clonidine was microinjected into the AHA of rats maintained on the four diets for 2 weeks to test the hypothesis that dietary Ca2+ supplementation prevents the previously observed NaCl-induced upregulation of alpha 2-adrenoceptors in AHA. Clonidine caused dose-dependent decreases in MAP that were greater in high NaCl rats than in controls. The Ca2+ supplementation prevented the exaggerated depressor response to clonidine in the high NaCl group, but not in the controls. The Ca2+ supplementation had no effect on pretreatment MAP or on MAP responses to clonidine in control NaCl-resistant SHR (SHR-R) or Wistar-Kyoto (WKY) rats. Thus, dietary Ca2+ supplementation prevents the NaCl-induced exacerbation of hypertension and augmented depressor response to clonidine in SHR-S by increasing noradrenergic input to AHA, thereby preventing the upregulation of AHA alpha 2-adrenoceptors.

Animals↗

PubMed1990

Atrial natriuretic factor prevents NaCl-sensitive hypertension in spontaneously hypertensive rats.

Our previous studies demonstrated that acute infusion of atrial natriuretic factor (ANF) produces an enhanced depressor response in NaCl-sensitive spontaneously hypertensive rats (SHR-S) fed a high (8%) NaCl diet compared with control SHR-S fed a normal (1%) NaCl diet and that dietary NaCl loading increases circulating ANF levels in Wistar-Kyoto (WKY) rats but not in SHR-S. The current study tested the hypotheses that 1) long-term infusion of ANF at a dose that elevates plasma ANF to levels comparable with those seen in high NaCl-fed WKY rats prevents the NaCl-induced exacerbation of hypertension in SHR-S and 2) ANF lowers blood pressure in this model by a sympatholytic effect. Male SHR-S received infusions of ANF (0.1 microgram/hr) or vehicle intravenously via osmotic minipump for 3 weeks beginning immediately before initiation of 1% or 8% NaCl diets at age 7 weeks. Chronic ANF infusion prevented the increase in arterial pressure in response to a high NaCl diet in SHR-S but had no effect in 1% NaCl-fed SHR-S. Thus, the NaCl-sensitive component of hypertension in SHR-S was more sensitive to ANF than the non-NaCl-sensitive component. Plasma norepinephrine was significantly increased in ANF-treated, 8% NaCl-fed SHR-S compared with vehicle controls, suggesting that ANF did not prevent NaCl-sensitive hypertension by a sympatholytic effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

NaCl does not affect hypothalamic noradrenergic input in deoxycorticosterone acetate/NaCl and Dahl salt-sensitive rats.

Previous studies from our laboratories demonstrated that dietary NaCl supplementation in NaCl-sensitive spontaneously hypertensive rats elevates blood pressure, increases peripheral sympathetic nervous system activity, and depresses endogenous norepinephrine stores and turnover in the anterior hypothalamus. These findings suggest that reduced noradrenergic input to sympathoinhibitory neurons in anterior hypothalamus contributes to NaCl-sensitive hypertension in spontaneously hypertensive rats. The current study tested the hypothesis that dietary NaCl supplementation depresses endogenous norepinephrine stores and turnover in anterior hypothalamus of two other NaCl-sensitive models of hypertension, the Dahl salt-sensitive rat and the deoxycorticosterone acetate/NaCl hypertensive rat, thus increasing blood pressure by reducing noradrenergic input to the anterior hypothalamus. Dahl salt-sensitive rats were fed a high (8%) NaCl diet, and deoxycorticosterone acetate/NaCl rats rats drank 1% NaCl solution ad libitum for 2 or 4 weeks. Age-matched Dahl salt-sensitive rats fed a basal 1% NaCl diet and uninephrectomized Sprague-Dawley rats drinking tap water were controls. Regional brain catecholamines were determined by high-performance liquid chromatography with electrochemical detection. Norepinephrine turnover in hypothalamus (anterior, posterior, and ventral regions) and brain stem (pons and medulla) was assessed using the dopamine beta-hydroxylase inhibitor 1-cyclohexyl-2-mercapto-imidazole. High NaCl treatment caused significant elevations in blood pressure in Dahl salt-sensitive and deoxycorticosterone acetate/NaCl rats, but endogenous norepinephrine levels and turnover rates were not significantly different in anterior hypothalamus or any other brain region studied between the NaCl-supplemented and control groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Interleukin-2 does not attenuate hypertension in spontaneously hypertensive rats.

It was recently reported that interleukin-2, when administered as a single bolus injection (5,000 units/kg), could prevent the development of hypertension in young spontaneously hypertensive rats and lower blood pressure to normotensive levels in spontaneously hypertensive rats with established hypertension. Consequently, efforts were made to duplicate this finding. Male spontaneously hypertensive rats (35 days old) were injected subcutaneously with 50,000 units/kg (3,500 units/rat) of recombinant interleukin-2 (Amgen) and had systolic blood pressure measured twice weekly by the tail-cuff technique. Systolic blood pressure in the interleukin-2-treated group was not significantly different from the vehicle-treated control group at any time point over 32 days of follow-up. A second injection of recombinant interleukin-2 (5,000 units/kg) was administered 32 days after the first injection. Again, no reduction in blood pressure was observed in the interleukin-2-treated group over an additional 38 days. Mean arterial pressure (+/- SEM) measured via intra-arterial cannula in conscious rats at age 105 days (38 days after the second treatment) was 168.5 +/- 3.5 mm Hg in interleukin-2-treated spontaneously hypertensive rats and 170.3 +/- 3.6 mm Hg in vehicle-treated controls. Both recombinant interleukin-2 preparations conformed to their respective manufacturer's indicated specific activity as determined by the ability of the interleukin-2 to induce proliferation of the interleukin-2-dependent cell line HT-2. Thus, this study demonstrated that interleukin-2 was ineffective in preventing or attenuating hypertension in spontaneously hypertensive rats.

Animals↗

PubMed1990

Blockade of endogenous anterior hypothalamic atrial natriuretic peptide with monoclonal antibody lowers blood pressure in spontaneously hypertensive rats.

We have previously shown that the atrial natriuretic peptide (ANP) content of the anterior hypothalamic region of NaCl-sensitive spontaneously hypertensive rats (SHR-S) is higher than that of Wistar-Kyoto (WKY) rats. ANP has been shown to inhibit neuronal norepinephrine release and to reduce the excitability of hypothalamic neurons. This study tested the hypothesis that blockade of endogenous ANP in the anterior hypothalamus by local microinjection of a monoclonal antibody to ANP (MAb KY-ANP-II) lowers blood pressure in SHR-S. Purified MAb KY-ANP-II (0.055 and 0.55 micrograms) or control mouse IgG in 200 nl saline was microinjected into the anterior hypothalamic area (AHA) of conscious SHR-S and control WKY rats. As a further control, Mab KY-ANP-II (0.55 microgram) was microinjected into the posterior hypothalamic area (PHA) of SHR-S. Anterior hypothalamic microinjection of MAb KY-ANP-II caused significant dose-related decreases in mean arterial pressure (MAP) and heart rate (HR) in SHR-S but not in WKY rats. Control injections of equal volumes of IgG had no effect on MAP or HR. Microinjection of Mab KY-ANP-II into PHA produced no significant alteration in MAP or HR in SHR-S. These data provide the first demonstration that endogenous ANP in a region of brain known to influence cardiovascular function mediates BP and HR control in the rat. These findings suggest that the increased endogenous ANP in the anterior hypothalamus of SHR-S may be involved in the central regulation of BP in the model.

Animals↗

PubMed1989

Dietary NaCl loading enhances antihypertensive effect of guanabenz in spontaneously hypertensive rats.

Our previous studies demonstrated that high dietary NaCl intake causes increases in blood pressure and plasma norepinephrine (NE) levels and a decrease in NE release associated with local upregulation of alpha 2-adrenoceptor number in the anterior hypothalamic area (AHA) of NaCl-sensitive spontaneously hypertensive rats (SHR-S). Further, acute microinjection of clonidine into the AHA of SHR-S fed a high NaCl diet resulted in greater depressor and bradycardic responses than in SHR-S receiving a normal NaCl diet. The current study tested the hypothesis that the antihypertensive effect of chronic systemic administration of guanabenz (0.24 micrograms/kg/min, IV) is enhanced in SHR-S maintained on a high (8%) NaCl diet than in control rats on a normal (1% NaCl) diet. After two weeks on the diets, mean arterial pressure (MAP) and heart rate (HR) were measured and blood for NE and epinephrine (E) assay was collected from intra-arterial cannulas in conscious, unrestrained rats. The ratio of left ventricle and septum to body weight (LV + S/BW) was determined. Chronic infusion of guanabenz significantly decreased MAP (P less than .05), HR (P less than .01) and LV + S/BW (P less than .01) in 8% NaCl fed SHR-S, but not in 1% NaCl fed SHR-S (P greater than .1). Guanabenz tended to reduce plasma NE levels in 8% NaCl fed SHR-S (.1 greater than P greater than .05), but not in 1% NaCl fed rats (P greater than .1).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗