摘要:

The cells in the renal medulla protect themselves from the extracellular hypertonicity in that region of the kidney by accumulating large amounts of sorbitol, inositol, grycerophosphorylcholine, and betaine. The system is uniquely active in this part of the body, but it represents a throwback to primitive mechanisms by which cells in virtually all organisms, including bacteria, yeasts, plants, and lower animals counteract water stress. In this brief review, we ummarize how these “compatible organic osmolytes” help the renal medullary cells to survive, the mechanisms by which the organic osmolytes are accumulated, and how the accumulation is controlled to adjust for changing extracellular NaCl and urea concentrations. The compatible organic osmolytes are all intermediates in important biochemical pathways, and although the medical consequences are not yet fully worked out, it is already apparent that inappropriate accumulation of these solutes has major pathophysiological consequences.

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Our study examines the long-term cardiovascular effects after a brief period of angiotensin converting enzyme (ACE) inhibitor treatment in young spontaneously hypertensive rats (SHR). SHR were treated with perindopril (3 mg/kg/day) by gavage from 2 to 6, from 6 to 10, or from 2 to 10 weeks of age. Systolic blood pressure was measured in the tail weekly until 25 weeks of age. Corresponding control groups received distilled water for the same periods. In each treatment group blood pressure was reduced significantly during treatment, rose when treatment stopped, but plateaued significantly below control SHR thereafter. This difference in blood pressure at 25 weeks of age was due to reduced total peripheral resistance as determined by microsphere methods, but plasma renin activity and angiotensin II concentrations were not different Cardiac hypertrophy was also reduced in treated SHR. In a separate experiment, perindopril treatment from 6 to 10 weeks of age resulted in a significant reduction in the media/ lumen ratios of mesenteric resistance vessels at 32 weeks of age. Concomitant administration of angiotensin II with perindopril from 6 to 10 weeks of age not only prevented the long-term effects on blood pressure seen with perindopril treatment alone but was associated with cardiovascular hypertrophy in excess of untreated control SHR. Finally, perindopril given for a shorter period (6 to 7 weeks) or later in life (20 to 24 weeks) had no significant long-term effects on blood pressure. These results demonstrate that a 4-week period of ACE inhibitor treatment in young SHR is sufficient to prevent the full expression of genetic hypertension and cardiovascular hypertrophy and that angiotensin II might be important in the development of hypertension in this model, its role in later life being less important.

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

During a survey of young subjects not receiving treatment for hypertension in Tecumseh, Michigan, clinic and self-monitored blood pressures taken at home (14 readings in 7 days) were obtained in 737 subjects (387 men, 350 women, average age 31.5 years). Hypertension in the clinic was diagnosed if the clinic blood pressure exceeded 140 mm Hg systolic or 90 mm Hg diastolic. In the absence of firm criteria for what constitutes hypertension at home, subjects whose average home blood pressure was in the upper decile of the whole population were considered to have hypertension at home. By these criteria, 7.1% of the whole population had “white coat” hypertension (i.e., high clinic but not elevated home readings). The prevalence of “sustained” hypertension (i.e., high readings in the clinic and at home) was 5.1%. Subjects with white coat and sustained borderline hypertension in Tecumseh were very similar. Both groups showed, at previous examinations (at ages 5, 8, 21, and 23 years), significantly higher blood pressure readings than the normotensive subjects. As young adults (average age 333 years), the parents of both hypertensive groups had significantly higher blood pressure readings than the parents of normotensive subjects. Both hypertensive groups had faster heart rates, higher systemic vascular resistance, and higher minimal forearm vascular resistance. Both hypertensive groups were more overweight, had higher plasma triglycerides, insulin, and insulin/glucose ratios than normotensive subjects. The white coat hypertensive group also had lower values of high density lipoprotein than the normotensive group. White coat hypertension is a frequent condition. In regards to excessive risk of hypertension (past blood pressures, parental blood pressures, weight, and heart rate), excessive risk for atherosclerosis (triglycerides and insulin), and hemodynamic parameters (vascular resistance and minimal forearm resistance), the white coat and sustained hypertensive groups are similarly different from the normotensive group. These findings do not support the accepted practice of using home blood pressure determination to distinguish groups of borderline hypertensive subjects with a lesser or greater clinical problem.

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Psychosomatic factors, sympathoneural and sympathoadrenal as well as cardiovascular mechanisms, were studied in 24 patients 18–24 years of age with borderline hypertension, 50 age-matched nonnotensive offspring of hypertensive parents, and 49 controls with no family history of hypertension. They were compared by projective and questionnaire-based psychological tests and their circulatory and neurohormonal reactivity to mental (Stroop color-word conflict test and arithmetic test) and physical stressors (orthostasis and bicycle ergometry test) were measured. Borderline hypertensive subjects externalized aggression less (p< 0.05) but internalized it more (p< 0.05) and were more submissive (p< 0.05) when compared with controls. Offspring of hypertensive parents showed a similar but weaker pattern. Both risk groups reported more positive interactions with their parents (genetic risk subjects versus controls,p< 0.05; borderline hypertensive patients versus controls,p= 0.08) and had higher state-anxiety levels (p< 0.05). There were more subjective symptoms of β-adrenergic receptormediated functions (e.g., tachycardia, tremor) in borderline hypertensive subjects and offspring of hypertensive parents, elevated heart rates (analysis of repeated measures,p< 0.001), and enhanced plasma norepinephrine concentrations (p< 0.05) when compared with controls. These findings in subjects at risk for the development of hypertension suggest that psychosomatic factors and sympathetic overactivity are involved in the early phase of hypertension.

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The rat zona glomerulosa has a renin-angiotensin system that appears to function as an autocrine or paracrine system in the regulation of aldosterone production. To further investigate dynamic changes of production of renin and aldosterone in vitro we developed a primary monolayer culture of rat adrenal glomerulosa cells in serum-free medium. Collagenase- dispersed glomerulosa cells were incubated in PFMR-4 medium containing 10% fetal calf serum for 48 hours; the medium was then replaced with serum-free PFMR-4 medium. The cell viability and the aldosterone secretion were stable over the additional 48 hours in the serum-free control medium. After incubation for 24 hours in the serum-free medium, the cells were exposed to high K+or adrenocorticotropic hormone (ACTH) for another 24 hours. ACTH stimulated aldosterone secretion, and this increased secretion was associated with an increase in renin activity (cell active renin, from 15.56±0.71 to 45.75±5.69; cell inactive renin, from 0.67±0.54 to 8.75±3.40; medium inactive renin, from 5.58±1.16 to 106.20±14.01 pg angiotensin I (Ang I)/μg protein/3 hr). Aldosterone was also stimulated by high K+. This increase was also associated with an increase in active renin in the cells (from 15.08±1.80 to 23.26±2.15 pg Ang I/μg protein/3 hr) and an increase in inactive renin in the medium (from 10.87±1.62 to 21.37±3.20 pg Ang I/μg protein/3 hr). Addition of the angiotensin converting enzyme inhibitor lisinopril attenuated both ACTH- and high K+-stimulated aldosterone secretion significantly. These data indicate that a local renin system may play a role in the regulation of aldosterone production.

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Acute coadministrations of an inhibitor of endopeptidase 24.11 (thiorphan) and a ligand (SC-46542) selective for the non-guanylate cyclase-llnked atriopeptin binding sites increases urinary sodium excretion to a greater degree in conscious spontaneously hypertensive rats than in normotensive Wistar-Kyoto rats. In the present study, we examined the effects of chronic 10-day intravenous infusions of SC-46542 (des[Phe106,Gly107,Ala116Gln116] atriopeptin-(103–126)) (0.1 mg/kg/hr), thiorphan (1.5 mg/kg/hr), and atriopeptin-(103–126) (100 ng/hr) alone or in combination on direct recording of mean arterial pressure in conscious spontaneously hypertensive rats. During an 11-day time-control infusion of isotonic saline vehicle (100 μl/hr), mean arterial pressure remained stable. Chronic infusion of atriopeptin-(103–126) decreased mean arterial pressure progressively over the first 3 days; then mean arterial pressure progressively rose to control level over the following 3 days and remained at control level for the remainder of the experiment Similarly, coinfusions of atriopeptin-(103–126) and SC-46542 or thiorphan, SC-46542 and thiorphan, or the triple infusion of atriopeptin-(103–126), SC-46542, and thiorphan had only transient effects on mean arterial pressure during 10-day infusions. SC-46542 alone had no effect on mean arterial pressure. Similarly, thiorphan alone had no effect on mean arterial pressure except at doses that blocked the acute pressor response to angiotensin I. Chronic infusions of atriopeptin-(103–126), SC-46542, and thiorphan alone or in combination are not effective long-term treatments for hypertension in spontaneously hypertensive rats.

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The renal microvascular responses of Wistar-Kyoto and spontaneously hypertensive rats to changes in perfusion pressure were compared using a juxtamedullary nephron microvascular preparation perfused in vitro with a physiological salt solution containing 5% albumin. In the spontaneously hypertensive rats, the internal diameters of arcuate and interlobular arteries and the proximal and distal afferent arterioles averaged 307±26, 52±2, 24±0.9, and 22±1.2 ftm, respectively, at 80 mm Hg. They were 18–35% smaller (p< 0.05) than the corresponding vessels measured in Wistar-Kyoto rats. In low calcium media, the arcuate and interlobular arteries and the proximal and distal afferent arterioles of spontaneously hypertensive rats exhibited a greater dilation than the vessels of Wistar-Kyoto rats. These observations suggest that the diameters of the preglomerular vasculature of the spontaneously hypertensive rats are reduced because of an elevated vascular tone rather than structural changes narrowing the lumen of these vessels. These results suggest that enhanced vascular tone in the preglomerular vasculature of juxtamedullary nephrons may contribute to the elevated renal medullary vascular resistance and resetting of the pressure-natriuretic relation previously observed in spontaneously hypertensive rats.

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

To determine whether the increased renal biosynthesis of thromboxane A2observed in young genetically hypertensive rats of the Lyon strain could be involved in the development of their hypertension, Lyon hypertensive female rats received either thromboxane synthetase inhibitors (Dazmegrel or OKY 046) or a thromboxane A2receptor antagonist (AH 23848) during their prehypertensive stage. Treatment from 5 to 9 weeks of age with Dazmegrel failed to reduce systolic blood pressure. When given from 3 to 9 weeks of age, Dazmegrel and OKY 046 induced a similar progressive and specific reduction (60%) in the urinary excretion of thromboxane B2that was associated with a transient decrease in blood pressure level with Dazmegrel and a longer lasting blood pressure-lowering effect with OKY 046. AH 23848, given according to the same schedule, normalized the blood pressure level. This effect persisted 1 week after the cessation of the treatment Interestingly, active doses of thromboxane synthetase inhibitors or of thromboxane A2receptor blocker required a 3-week delay to exhibit their antihypertensive properties. It is concluded that 1) the elevated production of thromboxane A2observed in young Lyon hypertensive rats is likely to participate actively in their blood pressure regulation and 2) this effect may be independent of its direct vasoconstrictor properties.

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID