Vascular reactivity in rats with glycerol-induced acute renal failure

Cardiovascular responses in rats with chronic renal failure

Cardiovascular responses were determined in rats with chronic renal failure (CRF) produced by five sixths nephrectomy and in sham-operated rats. The conscious systolic blood pressure of rats with CRF was significantly higher than the pressure in controls although, after anaesthesia, there were no significant differences in the mean arterial pressure between the two groups of rats. The pressor responses to noradrenaline in rats with CRF were not significantly different from those recorded in sham-operated controls. The bradycardia elicited by electrical stimulation of the vagus nerve was significantly diminished in rats with CRF. However, indomethacin treatment (1 mg kg-1 s.c. twice daily for 2 days) abolished the differences in response to vagal stimulation. Changes in heart rate in response to electrical stimulation of the cervical sympathetic nerve and to bolus i.v. injections of isoprenaline and carbachol were similar in rats with CRF and controls. The most notable disturbance of cardiovascular function in rats with CRF is the diminished cardiac chronotropic response to vagal stimulation which appears to be mediated by a presynaptic action of prostaglandins.

Actions of flavonoids and the novel anti-inflammatory flavone, hypolaetin-8-glucoside, on prostaglandin biosynthesis and inactivation

The newly identified plant-derived flavone-glycoside hypolaetin-8-glucoside, which has anti-inflammatory and gastric ulcer protective properties, and its corresponding aglycone, hypolaetin, were tested for effects on prostaglandin biosynthesis and degradation. They were compared with four other flavonoids, viz. rutin and its corresponding aglycone, quercetin, and the aglycones isoscutellarein and kaempferol. Over the range 10-1000 microM the glycosides rutin and hypolaetin-8-glucoside stimulated prostaglandin formation by sheep seminal vesicle microsomes incubated with radiolabelled arachidonic acid; the other compounds were essentially inactive. Over 5-5000 microM rutin and hypolaetin-8-glucoside enhanced the release of prostacyclin (and other prostanoids) from fragments of rat caecum incubated in the absence of additional arachidonic acid; the four aglycones compounds did not stimulate prostacyclin release but some reduced it at 5000 microM. However, the glycosides did not affect the enzymatic inactivation of radiolabelled prostaglandin F2 alpha by semi-purified bovine lung prostaglandin 15-hydroxydehydrogenase (PGDH) or in 100,000 g supernatants prepared from homogenised rat stomach. Three of the four aglycones (quercetin, kaempferol, isoscutellarein, in descending order of potency) were inhibitory to PGDH with ID50 values in the range 130-2100 microM. The results show that the capacity of flavonoids to enhance prostaglandin formation is associated with the presence of glycosidic substitution, whereas PGDH inhibition requires its absence. The relevance of this biochemical profile of hypolaetin-8-glucoside to its anti-inflammatory gastroprotective effects in vivo is discussed.

Vascular reactivity in experimental acute renal failure

Vascular reactivity in-vivo and in-vitro was examined in rats with acute renal failure produced by bilateral nephrectomy or intramuscular glycerol injection. Bilaterally nephrectomized rats displayed enhanced pressor responses to noradrenaline and angiotensin. However, the contractile responses to noradrenaline, angiotensin and potassium chloride of aortic rings and portal vein segments from nephrectomized rats were not significantly different from the responses obtained in vessels from sham-operated controls. Rats with glycerol-induced ARF which were pretreated with indomethacin had significantly lower pressor responses to noradrenaline and angiotensin than similarly treated control animals. Aortic rings from glycerol-injected rats produced significantly smaller contractions to noradrenaline than preparations from controls. This difference was not abolished by incubation of vessels with indomethacin. The findings suggest that the absence of kidneys or the presence of damaged renal tissue and not uraemia itself have pronounced but opposite effects on vascular reactivity. The depression of vascular reactivity in glycerol-induced ARF does not appear to be a result of increased production of prostaglandins.

Cardiovascular responses in spontaneously hypertensive rats with acute renal failure

Cardiovascular status and reactivity have been investigated in spontaneously hypertensive rats (SHR) with glycerol-induced acute renal failure. SHR with acute renal failure had significantly lower mean arterial blood pressures and heart rates. The pressor responses to noradrenaline and the chronotropic responses to right cervical sympathetic and vagal nerve stimulation were diminished in uraemic SHR compared to control SHR. The cardiovascular depression observed in SHR with acute renal failure was similar to that previously noted in normotensive rats with acute renal impairment.