摘要:

To determine whether the increased thickness seen in media of mesenteric resistance vessels of Wistar-Kyoto rats made hypertensive by a Goldblatt procedure (one-kidney, one clip model) was due to hypertrophy or hyperplasia of smooth musde cells, the cellular dimensions of these vessels were estimated using a new, unbiased stereoJogkal method (the disector). Furthermore, to investigate whether the changes seen could be secondary to the increased blood pressure, morphometric measurements were also made in renal arcuate arteries, which, due to the constricting silver clip, probably had not been exposed to the increased pressure load. Vessels were mounted on a myograph, and their media thickness, lumen diameter, and maximum active wall tension response were measured. In the mesenteric vessels media thickness had increased by 58%, whereas no changes were seen In the renal vessels. Vessels were then fixed, and serial sections were made in the mesenteric vessels. The disector was used to calculate the numerical cell density in each vessel. By combining the myograph measurements and the estimated numerical cell density, the number of cells per segment unit length was calculated (renal hypertensive rats, 6.8 μm−1; sham-operated Wistar-Kyoto rats, 6.3 μm−1;Pgt; 0.40) and mean cell volume was determined (renal hypertensive rats, 1541 μm3; sham-operated Wistar-Kyoto rats, 1256 μm3;p< 0.02). No morphometrkal changes were found hi single sections of the renal arteries. We conclude that the Increased media thickness observed in mesenteric resistance vessels of one-kidney, one dip Goldblatt hypertensive rats mainly was caused by smooth muscle cell hypertrophy.

ISSN:0194-911X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

This study evaluated whether pressure-diuretic and pressure-natriuretlc responses are associated with alterations in vasa recta hemodynamics. Autoregulation of cortical and papillary blood flow was studied using a laser-DoppIer flowmeter in volume-expanded and hydropenk rats. Superficial cortical flow and whole kidney renal blood flow were antoregulated in volume-expanded rats and decreased by less than 10% after renal perfusion pressure was lowered from 150 to 100 mm Hg. In contrast, papillary blood flow was not autoregulated and fell by 24 ± 2%. The failure of papillary blood flow to autoregulate was due to changes in the number of perfused vessels as well as to alterations In blood flow in individual ascending and descending vasa recta. Pressure hi vasa recta capillaries increased from 6.8 ± 0.8 to 13.8 ± 1.2 mm Hg after renal perfusion pressure was elevated from 100 to 150 mm Hg, and renal Interstitial pressure rose from 7.4 ± 0.8 to 12.3 ± 1.4 mm Hg. In hydropenic rats, papillary blood flow was autoregulated to a significant extent, but it still decreased by 19% after renal perfusion pressure was lowered from 150 to 100 mm Hg. The pressure-diuretic and presure-natriuretic responses in hydropenic rats were blunted in comparison to those observed in volume-expanded rats. These findings indicate that the pressure-diuretic and pressure-natriuretic responses are associated with changes in vasa recta hemodynamics and renal interstitial pressure.

ISSN:0194-911X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Micropuncture experiments were performed in volume-expanded rats to better define the nephron segments in which changes in renal perfusion pressure inhibit tubular reabsorption. Neural influences on the kidney were eliminated by renal denervation, and plasma levels of vasopressin, aldosterone, cortkosterone, and norepinephrine were maintained at fixed levels by i.v. infusion. Fractional excretion of sodium, chloride, and water increased markedly after renal perfusion pressure was elevated from 110 to 150 mm Hg. Renal blood flow, glomerular filtration rate, and single nephron glomerular filtration rate measured from deep and superficial nephrons were unaltered. Reabsorption of chloride and water in the proximal tubule of superficial nephrons decreased by 10% after renal perfusion pressure was elevated and contributed to the pressure-diuretic response. Changes in renal perfusion pressure also altered the reabsorption of water and chloride in juxtamedullary nephrons. The percentage of the filtered water load reaching the tip of the loop of Henle increased from 19.8 ± 2.9 to 38.1 ± 3.0% after renal perfusion pressure was elevated. Chloride delivery rose from 34.2 ± 4.3 to 65.2 ± 4.8% of the filtered load. These results support the view that alterations in medullary hemodynamks participate in the pressure-natriuretk response by inhibiting tubular reabsorption in the proximal tubule or the thin descending limb of the loop of Henle (or both) of juxtamedullary nephrons.

ISSN:0194-911X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

This study evaluated the possibility that hi hypertension, mechanisms that maintain near normal arteriolar diameters at elevated arteriolar pressures limit the ability of skeletal muscle arterioles to dilate hi response to an increase hi tissue metabolism. The spinotrapezius muscles of 16- to 20-week-old spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were contracted at frequencies of 1, 2, 4, and 8 Hz. The inner diameters of first-order through third-order arterioles were measured at rest and following 3 minutes of contractions. Tissue oxygen tension (PO2) at the venous end of capillaries was monitored during 8-Hz contractions. At rest, following contractions, and after nurrimnm dilation with adenosine, the inner diameters of arterioles of equivalent branch order were not significantly different hi SHR and WKY. Opening of closed arterioles during musde contraction and adenosine application occurred hi less than 5% of the observations hi both groups. The resting tissue Po2was 25.5 ± 1.3 mm Hg hi normal rats and 26.1 ± 2.1 mm Hg hi SHR. At nearly maximum vasodilation during 8-Hz stimulation, tissue PO2] recovered to 81.9 ± 12.7% of control In WKY but only to 41.2 ± 13.0% of control hi SHR. These observations indicate that the expression of local regulatory mechanisms related to tissue metabolism is virtually normal In the spinotrapezius muscle vasculature of SHR in the context of arteriolar dilation. However, at near maTinwni performance, factors other than absolute arteriolar diameter preclude the normal preservation of tissue PO2in the spinotrapezius musde of SHR.

ISSN:0194-911X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Atria] natriuretic factor (ANF) may be physiopathotogkally involved in several clinical conditions including human hypertension. However, few data are available regarding this putative hormone and its relationship to aldosterone, blood pressure, and vascular responsiveness to α-adrenergic receptor stimulation in primary aldosteronism, a volume-expanded, low-renin model of human hypertension. For this reason, the behavior of supine and upright plasma ANF as related to aldosterone, blood pressure, and forearm a-adrenergk sensitivity (plethysmographic technique) to intra-arterial norepinephrine infusion was studied in eight patients with primary aldosteronism (five with adenomas, three with hyperplasia) before and at the end of two sequential 1-week low (20 mmol/day) and high sodium (200 mmol/day) diet periods. Basal, prediet ANF concentrations decreased and increased after low and high sodium intakes, respectively. Furthermore, highly significant postural ANF decrements after 1 hour of standing occurred with each diet, although they were lower after the low than after the high sodium diet. Plasma aldosterone, either supine or upright, was insensitive to dietary sodium manipulations, suggesting the absence of ANF-mediated control of aldosterone secretion in our patients. In spite of about twofold higher ANF concentrations during the high than during the low sodium diet, forearm vascular sensitivity to intra-arterial norepinephrine infusion did not change during the study. Furthermore, systemic arterial blood pressure rose to a highly significant extent after dietary sodium content was increased, thus casting doubt on a role for ANF as an endogenous long-term modulator of systemic blood pressure and peripheral α-adrenergk sensitivity in patients with primary aldosteronism.

ISSN:0194-911X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

We examined the relationships between erythrocyte (RBC) composition (Na+,K+, and water content) and ouabain-insensitive transports (Na+-K+cotransport, Li+-Na+countertransport) and forearm vascular bemodynamks under standardized basal conditions and during vasoconstriction (intra-arterial infusion of graded doses of norepinephrine and angiotensin II) and vasodilation (intraarterial phentolamme and postischemic exercise). RBC water content correlated positively and significantly (r= 0.53,p= 0.001) with minimum forearm vascular resistance, a measure of vascular structural change, and negatively with nundinal forearm blood flow (r= − 0.55,p< 0.001). Similar correlations with forearm vascular resistance and blood flow were observed under all experimental conditions. RBC Na+-K+cotransport correlated positively and significantly (r= 0.43,p= 0.01) with the change in forearm blood flow produced by phentotamine, a functional measure of α-adrenergk tone, and was as strong an independent predictor of phentolamine-induced blood flow change as was arterial norepinephrine concentration. RBC Na+-K+cotransport was also significantly positively correlated with residual forearm blood flow and resistance after phentolamine administration, where nonadrenergk influences predominate. RBC water correlated negatively with LI+-Na+countertransport (r= −0.33,p< 0.05) and Na+-K+cotransport (r= −0.44,p< 0.01). We propose that RBC water is a marker for a vascular structural property that contributes to vascular reactivity. RBC Na+-K+cotransport seems to relate most strongly to the sympathetically mediated control of forearm blood flow and may also be linked to the intrinsic myogenk tone of the forearm vasculature. Li+-Na+countertransport is not significantly correlated with vascular hemodynamk measures but may, along with Na+-K+cotransport, relate to the control of cell composition.

ISSN:0194-911X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Increased blood pressure and left ventricular mass are associated with increased morbidity and mortality in adults with coronary heart disease. To define the predictors of subsequent childhood blood pressure and left ventricular mass, serial echocardiograms and blood pressure responses during exercise were studied in 274 children aged 6 to IS years, whose systolic blood pressures were in the high, middle, or low range. Persistence of rank order for left ventricular mass and blood pressure, at rest and during exercise, was maintained over a mean follow-up period of 3.4 years, with correlations ranging from 0.33 to 0.44. Subsequent systolic blood pressure was best predicted from initial resting and maximal exercise systolic blood pressures and left ventricular mass. Subsequent left ventricular mass was best predicted from initial left ventricular mass and maximal exercise diastolic blood pressure, but resting systolic blood pressure did not add to this latter prediction. Since left ventricular mass relates best to exercise blood pressure and not to resting Mood pressure, left ventricular mass may provide an integrated view of the effects of blood pressure both at rest and during stress. We speculate that increased left ventricular mass in childhood may be an important predictor of subsequent hypertension and its consequences.

ISSN:0194-911X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

The baroreceptor control of the sinus node was evaluated in 10 normotensive and 10 age-matched essential hypertensive subjects in whom ambulatory blood pressure was recorded intraarterially for 24 hours and scanned by a computer to identify the sequences of three or more consecutive beats hi which systolic blood pressure (SBP) and pulse interval (PI) progressively rose (+ PI/ + SBP) or fell (− PI/ −SBP) in a linear fashion, according to a method validated in cats. In normotensive subjects, several hundred +PI/+SBP and −PI/−SBP sequences of 3 beats were found whereas the number of sequences of 4,5, and more than 5 beats showed a progressive drastic reduction. The mean slopes of plus; PI/ + SBP (7.6 ± 2.0 msec/mm Hg) and − PI/− SBP (6.4 ± 1.5 msec/mm Hg) sequences were similar, but in both instances there was a large scattering of the values around the mean (variation coefficients: 64.2 ± 4.7 and 62.6 ± 2.4%). The slopes decreased as a function of the sequence length and baseline heart rate and increased to a marked extent during the night as compared with daytime values. All sequences were more rare (−33.2% for +PI/ + SBP and −31.7% for −PI/−SBP) and less steep in hypertensive subjects (−40.3 and −36.2%, respectively), who failed to show the marked nighttime increase in slope observed in normotensive subjects. To our knowledge, these observations provide the first description in humans of the baroreceptor-heart rate reflex in daily life. This reflex is characterized by marked within-subject variations hi sensitivity due in part to hemodynamic, temporal, and behavioral factors. All features of the baroreceptor-heart rate reflex are unpaired hi essential hypertension.

ISSN:0194-911X    

出版商:OVID    

年代:1988

数据来源: OVID