4-acetamido-4--isothiocyanatostilbene-2-2--disulfonic-acid and Hypertension

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Animals; Biological Transport, Active; Calcium; Cell Membrane; Cesium; Diffusion; Electrochemistry; Humans; Hypertension; Ion Channels; Kinetics; Magnesium; Mathematics; Ouabain; Potassium; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Rubidium; Sodium; Sodium-Potassium-Exchanging ATPase; Tissue Distribution

To study the activity of the Na(+)-dependent Cl(-)-HCO3- anion exchanger in erythrocytes of patients with essential hypertension.. The study was performed in cells from 48 untreated essential hypertensive patients and 30 normotensive controls with similar age- and sex- distribution.. The activity of the Na(+)-dependent anion exchanger was determined by measuring the 4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS) sensitive Li+ influx in fresh cells incubated into a medium containing Li2CO3.. The DIDS-sensitive Li+ influx was higher in hypertensives than controls. With the 100% confidence (upper) limit of the normotensive population as a cut-off point, a subgroup of 11 hypertensives had an abnormally high activity of the Na(+)-dependent Cl(-)-HCO3- anion exchanger. Compared with patients with normal exchanger activity, patients with increased exchanger activity were characterized by the following: higher frequency of family history of hypertension; lower serum high-density lipoprotein cholesterol levels and higher plasma aldosterone concentrations. After multiple regression analysis, the DIDS-sensitive Li+ influx was inversely correlated with high-density lipoprotein cholesterol levels.. These results show the presence of a new abnormality of erythrocyte Na+ transport in essential hypertension--increased activity of the Na(+)-dependent Cl(-)-HCO3- anion exchanger. In addition, our findings suggest that from the clinical point of view, patients with this transport abnormality represent a particular subset of essential hypertensives.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Adult; Aged; Aged, 80 and over; Biological Transport; Carrier Proteins; Chloride-Bicarbonate Antiporters; Erythrocytes; Female; Humans; Hypertension; Lithium; Male; Middle Aged; Regression Analysis; Sodium

To investigate intracellular pH (pHi) in human resistance arteries in essential hypertension, vessels were obtained from small biopsies of skin and subcutaneous fat from 14 untreated patients, and the results were compared with those from 14 matched normotensive control volunteers. Segments of isolated resistance arteries were mounted in a myograph and loaded with the pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. Fluorescence signals were monitored using a series of barrier filters and chromatic beam splitters. In this way both resting pHi and the changes in pHi observed during isometric contractions initiated by agonists could be recorded. Resting pHi was not different in vessels from hypertensive patients (hypertensive, 7.24 +/- 0.06 versus control, 7.25 +/- 0.04 pH units). The application of ethylisopropylamiloride (EIPA) and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) demonstrated that both Na(+)-H+ exchange and bicarbonate-dependent membrane mechanisms contributed to pHi homeostasis but that neither system was overactive in hypertension (pHi change with EIPA in vessels from hypertensive versus control subjects was -0.11 +/- 0.02 and 0.13 +/- 0.03 pH units, respectively, and pHi change with DIDS in vessels from hypertensive versus control subjects was -0.097 +/- 0.05 and -0.091 +/- 0.03 pH units, respectively). The application of norepinephrine or 125 mM K+ solution induced contraction in the arterial segments with an accompanying fall in pHi. With norepinephrine this fall was significantly attenuated in vessels from hypertensive patients. These results fail to provide evidence for raised pHi in resistance arteries in human essential hypertension, and contrary to previous reports in circulating blood cells, Na(+)-H+ exchange is not overactive in the vessels of such patients.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Adipose Tissue; Amiloride; Anti-Arrhythmia Agents; Arteries; Bicarbonates; Biological Transport; Calibration; Carrier Proteins; Female; Fluoresceins; Homeostasis; Humans; Hydrogen-Ion Concentration; Hypertension; Male; Middle Aged; Norepinephrine; Potassium; Skin; Sodium-Hydrogen Exchangers; Vascular Resistance

1. We have previously shown that the cytosolic acid concentration changes in skeletal muscle during contraction in spontaneously hypertensive rats and normotensive Wistar-Kyoto rats in vivo. We have now found that this change was unaffected by 20% inhaled CO2 or by 4,4'-di-isothiocyanostilbene-2,2'-disulphonate. This is evidence that HCO3- exchange in vivo is not important in the control of cytosolic acid concentration during skeletal muscle contraction in either spontaneously hypertensive or Wistar-Kyoto rats. 2. We have also previously shown that the difference in cytosolic acid response during contraction between spontaneously hypertensive and Wistar-Kyoto rats is due to increased Na+/H+ antiporter activity in the spontaneously hypertensive rats. Our current findings suggest that this increase in Na+/H+ antiporter activity is more likely to be due to a change in the Km of the antiporter than to a change in the Vmax. We estimate that the Km of the antiporter changes in hypertension from pH 7.16 to 7.33. 3. We did not find any differences between adult spontaneously hypertensive and Wistar-Kyoto rats with regard to resting intracellular and extracellular pH and resting intracellular and extracellular HCO3- concentrations. In addition, we did not find any evidence of a difference in skeletal muscle HCO3-/Cl- exchange between adult spontaneously hypertensive and Wistar-Kyoto rats. 4. At rest, skeletal muscles of the spontaneously hypertensive and Wistar-Kyoto rats have the same lactate production, HCO3-/Cl- exchange and arterial partial pressure of CO2. In addition, we can also calculate that at a resting intracellular pH of 7.05 in the spontaneously hypertensive rats, the antiporter is 66% saturated.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Animals; Antiporters; Bicarbonates; Carbon Dioxide; Carrier Proteins; Chlorides; Cytosol; Hydrogen; Hydrogen-Ion Concentration; Hypertension; Ion Exchange; Male; Membrane Proteins; Muscle Contraction; Muscles; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Sodium

In order to investigate the membrane-located mechanisms that control intracellular pH in resistance arteries, mesenteric vessels from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) at 5 weeks of age were mounted in a myograph and loaded with 2',7'-bis(carboxyethyl)5,6-carboxyfluorescein (BCECF). Resting intracellular pH was studied over 10 min in the presence of amiloride (1 mmol/l), or 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS; 0.2 mmol/l). In the presence of DIDS, there was no significant difference in the resulting fall in intracellular pH over 10 min between rat strains. However, in the presence of amiloride there was a significantly greater fall in intracellular pH in SHR (P less than 0.001). These data indicate that in the resting state Na(+)-H+ exchange is increased in SHR resistance arteries at the time when blood pressure is rising and vascular remodelling is taking place.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Amiloride; Animals; Fluoresceins; Fluorescent Dyes; Hydrogen-Ion Concentration; Hypertension; In Vitro Techniques; Male; Mesenteric Arteries; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Stilbenes; Vascular Resistance

Chronic infusion of d-aldosterone into uninephrectomized rats on high sodium intake resulted in a significant increase in systolic blood pressure. The steady state efflux of 36Cl in aorta and femoral artery of hypertensive rats was significantly elevated compared to that in arteries of control rats. These elevations in chloride efflux persisted in the presence of the Cl-HCO3 exchange inhibitor, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), and in Cl-HCO3 free solution. The Cl-HCO3-dependent component of the 36Cl efflux was also higher under some conditions. DIDS (100 mumol/l), also significantly reduced the increase in 36Cl efflux caused by norepinephrine (NE) in one of four groups, but had no significant effect on the NE stimulated 42K efflux. Contractile responses to both NE and KCl were unaffected by DIDS treatment. Therefore, it appears that Ca influx and release mechanisms function normally in the presence of DIDS. Similarly, DIDS had either a small or no effect on 42K movements under basal conditions. A slight reduction in the passive efflux of 24Na was observed in aortic smooth muscle exposed to DIDS with no significant effect on active Na transport. These findings indicate that DIDS is reasonably selective for Cl exchange sites in vascular smooth muscle during an exposure of 15 min or less and has little effect on cationic transport processes. The application of this blocker as well as anion substitution indicates that an elevation in the 36Cl leak efflux and related Cl permeability of arterial smooth muscle is associated with aldosterone-salt hypertension.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Aldosterone; Animals; Biological Transport, Active; Chlorides; Hypertension; Ion Channels; Male; Muscle Contraction; Muscle, Smooth, Vascular; Rats; Rats, Inbred Strains; Sodium, Dietary

Evidence is presented for the operation of Cl-Cl exchange diffusional transport system in rat aortic smooth muscle. The efflux of 36Cl associated with this mechanism is doubled in rats made hypertensive with aldosterone-salt treatment. The residual efflux of Cl is similarly elevated in the hypertensives. This finding supports the hypothesis that increased membrane permeability to Cl is associated with aldosterone hypertension. The agonist-induced increases in aortic effluxes of 42K exhibit a 10-fold reduction in the ED50 to norepinephrine in aldosterone hypertensive rats. The possible contributors to this supersensitivity were studied by means of a pharmacologic analysis of the action of competitive (phentolamine) and non-competitive (dibenamine) antagonism of norepinephrine induced increases in 42K efflux. The dissociation constant for phentolamine, KB= 1 x 10-8M, was relatively unaltered in the hypertensive group, as was the dissociation constant for norepinephrine, KA= 3.4 - 5.8 x 10-7M. A substantial increase in receptor number and/or transduction efficiency (3-12 fold) was derived from the analysis. It is tentatively concluded that supersensitivity to norepinephrine during aldosterone hypertension may be more closely related to changes in receptor number and/or efficiency than in receptor affinity.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Animals; Aorta; Biological Transport; Cell Membrane; Cell Membrane Permeability; Chlorides; Dibenzylchlorethamine; Hypertension; Male; Muscle Contraction; Muscle, Smooth, Vascular; Norepinephrine; Phentolamine; Rats; Rats, Inbred Strains

Opening of the blood-brain barrier (BBB) by a hypertensive insult comprises the formation of endothelial micropinocytosis. Constricted vessels are less vulnerable to the insult. In the present study SITS (4-acetamido-4'-isothiocyano-stilbene-2,2'-disulfonic acid disodium) was shown to prevent leakage across the BBB into the brain parenchyma following a hypertensive insult induced by a local increase of the intraluminal pressure in anesthetized rats and by i.v. administration of adrenaline or bicuculline in conscious unrestrained animals. Since SITS induced an increase in cerebral blood flow the protection cannot be explained by a constrictory action on the cerebral vessels. SITS is a drug with complex action on the cell membrane including an inhibitory effect on anion transport mechanisms and on some c-AMP mediated processes. It is possible that the protection of BBB observed in the present study is connected to a reduction of c-AMP but membrane stabilizing effect can at present not be excluded.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; Animals; Bicuculline; Blood-Brain Barrier; Cell Membrane; Cerebrovascular Circulation; Cyclic AMP; Epinephrine; Hypertension; Male; Pinocytosis; Rats; Stilbenes

Cerebral air embolism can have hemodynamic effects such as increases in blood pressure and cerebral blood flow. It has been suggested that these factors play a role for the induction of the blood-brain barrier (BBB) dysfunction. In the present study, 5 microliters air was injected into the right internal carotid artery from a catheter in the external carotid artery after ligation of the extracerebral branches. No consistent change in blood pressure was observed with this small amount of air. Hypercapnia, which increases protein leakage in the brain under conditions of high intraluminal pressure, significantly reduced the extravasation in air embolism. Lidocaine and SITS (4 acetamido-4-isothiocyano-stilbene-2,2-disulfonic acid disodium), two drugs that effectively reduce the albumin leakage in acute hypertension, had no prophylactic effect in cerebral air embolism. Spontaneously hypertensive rats are less vulnerable than normotensive rats to pressure-induced BBB dysfunction but did not significantly differ from controls regarding albumin leakage in the present study. It is concluded that the increased cerebrovascular permeability in air embolism is not related to hemodynamic factors.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; Animals; Blood Pressure; Blood-Brain Barrier; Carbon Dioxide; Embolism, Air; Evans Blue; Hydrogen-Ion Concentration; Hypertension; Intracranial Embolism and Thrombosis; Lidocaine; Male; Rats; Serum Albumin, Radio-Iodinated; Vasodilation