Long-term ingestion of Hibiscus sabdariffa calyx extract enhances myocardial capillarization in the spontaneously hypertensive rat.

The effects of Hibiscus sabdariffa (HS) in lowering blood pressure in human and animal hypertension have been documented. This study investigated the effect of the water extract of the dried calyx of HS and Hibiscus anthocyanins (HAs) on left ventricular myocardial capillary length and surface area in spontaneously hypertensive rats (SHRs). Twelve-week-old male SHRs were divided into eight groups (six rats in each group). Three groups were given three doses; 10%, 15% and 20% of the water extract of HS in lieu of drinking water for 10 consecutive weeks (HS10, HS15 and HS20) with one group kept as control (C). Another three groups were given three doses of the HAs orally at doses of 50, 100 and 200 mg/kg for five consecutive days with one group kept as a control (C). Systolic (SBP) and diastolic (DBP) blood pressures, as well as heart rate (HR), were measured weekly. After the experimental protocols, the left ventricles (LV) of all rats were obtained. Capillary surface area density and length density were determined by unbiased sterological methods on 3 µm LV tissue samples from perfusion-fixed hearts. HS ingestion significantly reduced SBP, DBP and LV mass in a dose-dependent fashion but did not affect the HR. HS significantly increased surface area and length density of myocardial capillaries by 59%, 65% and 86%, and length density by 57%, 77% and 57%, respectively. Myocyte nuclear volume was significantly decreased in HS-treated rats. There was a decrease (although insignificant) in SBP and DBP with HA ingestion compared with controls. These changes suggest that the observed beneficial effect of HS on high BP in SHRs could be mediated through a reduction in the diffusion distance between capillaries and myocytes, as well as new vessel formation. It is proposed that these effects might be beneficial in restoring myocyte normal nutritional status compromised by the hypertrophic state of hypertension.

Effect of Hibiscus sabdariffa and its anthocyanins on some reproductive aspects in rats.

An aqueous extract of Hibiscus sabdariffa L. is a common beverage in many parts of the world. Reports on its effect on reproduction are conflicting, with anecdotal evidence that the plant is an aphrodisiac, while others report that it is estrogenic, and adversely affects spermatogenesis in rats. We have studied the effect of different concentrations of aqueous extracts of H. sabdariffa calyces (10%, 15% and 20%) used as drinking water for 10 consecutive weeks, and its anthocyanins (50, 100, 200 mg/kg for 5 days, orally) on the weight and histology of the testis, and on some biochemical constituents in testicular homogenates, in addition to the plasma concentrations of testosterone, luteinizing hormone and estradiol. The possible presence of an estrogenic effect of the extract and anthocyanins on the uteri of immature female rats was also tested. Neither the H. sabdariffa extract nor the anthocyanins significantly altered either testicular weight and histology, or uterus weight. Plasma concentrations of the three hormones studied, the testicular concentrations of protein, reduced glutathione and total cholesterol, and superoxide dismutase activity were all insignificantly affected by either the extract or the anthocyanins, except for a slight, but statistically significant, decrease in testicular protein concentration caused by the 15% aqueous extract when compared with controls. These results suggest that H. sabdariffa exerts no adverse effect on the male reproductive system. Consumption of H. sabdariffa aqueous extract inhibited the growth of the rats compared with the controls.

Effect of Acacia gum on blood pressure in rats with adenine-induced chronic renal failure.

Chronic renal failure (CRF) occurring naturally in patients or induced by subtotal nephrectomy in rats induces several alterations in the cardiovascular system (CVS). However, the effect of chemically induced CRF in rats on the CVS is less well known. We induced CRF in rats by feeding adenine (0.75%, w/w, four weeks) and investigated the effect of the ensuing CRF on the systolic and diastolic blood pressure (BP) and heart rate (HR). Further, we investigated the effect of giving acacia gum (AG, 10%, w/v) in the drinking water concomitantly with adenine on the above parameters. AG has been previously shown to ameliorate the severity of CRF in humans and rats. We confirmed here that adenine-induced CRF significantly increased the plasma concentrations of urea and creatinine, and reduced creatinine clearance. Additionally, it significantly increased both systolic and diastolic BP, with no significant effect on HR. Both of these actions were significantly mitigated by AG treatment. The antihypertensive angiotenisn-converting enzyme inhibitor lisinopril (10mg/kg) was given by gavage to rats concomitantly with adenine, significantly reduced the rise in blood pressure induced by adenine. In conclusion, adenine-induced CRF in rats significantly increased BP, and this was significantly mitigated by administration of AG. Possible mechanisms of these changes and the protective effect of AG will be investigated.

Motor and behavioral changes in rats with adenine-induced chronic renal failure: influence of acacia gum treatment.

Chronic renal failure (CRF) either occurring naturally in humans or induced surgically in rats causes alterations in behavior and motor functions. However, the effect of chemically induced CRF in rats on behavior is not known. We induced CRF in rats by feeding adenine (0.75% w/w, four weeks) and investigated the effect of the ensuing CRF on a depression model (forced swimming test, FST), analgesia (mechanical nociception), neuromuscular coordination (Rota-rod test) and motor activity (activity meter test). Further, we investigated the effect of giving acacia gum (AG, 10% w/v) in the drinking water concomitantly with adenine using the above models. AG has been previously shown to ameliorate the severity of CRF in humans and rats. Adenine-induced CRF significantly increased the plasma concentrations of urea and creatinine, and reduced creatinine clearance. Additionally, it significantly reduced motor activity and increased immobility time in the FST, suggesting a depressant-like effect. Both of these actions were significantly antagonized by AG treatment. Adenine insignificantly reduced the mechanical nociceptive threshold by 15%. The results of the tests for neuromuscular coordination were inconclusive. In conclusion, adenine-induced CRF caused motor and behavioral alterations, and these were significantly mitigated by administration of AG.

Additional salutary effects of the combination of exercise training and an angiotensin-converting enzyme inhibitor on the left ventricular function of spontaneously hypertensive rats.

OBJECTIVES: To investigate whether the combination of exercise training with the angiotensin-converting enzyme inhibitor lisinopril will have an additional beneficial effect on left ventricular function in spontaneously hypertensive rats. DESIGN: Twelve-week-old male rats were assigned to treadmill running (Ht-Ex; 20 m/min at 5 degrees grade, 1 h/day, 5 days/week), or lisinopril treatment (Ht-Lis; 15 mg/kg per day by gavage), or treadmill running while treated with lisinopril (Ht-ExLis), and were compared with a sedentary group (Ht-Sed). Age-matched and sex-matched Wistar-Kyoto rats were controls. METHODS: After 10 weeks of experimentation, left ventricular morphology and function were assessed from M-mode echocardiograms and transmitral Doppler spectra [early (E) and atrial peak velocities (A), their ratio (E/A), and E-wave deceleration time (Edec time) and slope (Edec slope)]. RESULTS: Ht-Sed exhibited prominent concentric left ventricular hypertrophy with systolic and diastolic dysfunctions evidenced by a significantly reduced fractional shortening (%FS) and 'pseudonormalization' of left ventricular filling, characterized by an apparently normal E/A ratio despite an underlying left ventricular relaxation abnormality. Exercise training did not significantly alter left ventricular morphology or function. Lisinopril alone attenuated left ventricular hypertrophy and enhanced diastolic function but had no significant effect on systolic function. Combining exercise training with lisinopril treatment increased %FS by 25%, decreased the E/A ratio and Edec slope by 35% and 37%, respectively, and increased Edec time by 82%. CONCLUSION: Our results provide experimental evidence that lisinopril administration, when combined with moderate exercise training, is more promising in attenuating cardiac dysfunction than either agent alone in hypertension of a genetic origin.

Biological effects of gum arabic: a review of some recent research.

Gum arabic (GA) is a branched-chain, complex polysaccharide, either neutral or slightly acidic, found as a mixed calcium, magnesium and potassium salt of a polysaccharidic acid. The backbone is composed of 1,3-linked beta-D-galactopyranosyl units. The side chains are composed of two to five 1,3-linked beta-D-galactopyranosyl units, joined to the main chain by 1,6-linkages. Pharmacologically, GA has been claimed to act as an anti-oxidant, and to protect against experimental hepatic-, renal- and cardiac toxicities in rats. These reports could not be confirmed by others. GA has been claimed to alleviate the adverse effects of chronic renal failure in humans. This could not be corroborated experimentally in rats. Reports on the effects of GA on lipid metabolism in humans and rats are at variance, but mostly suggest that GA ingestion can reduce plasma cholesterol concentrations in rats. GA has proabsorptive properties and can be used in diarrhoea. It enhances dental remineralization, and has some antimicrobial activity, suggesting a possible use in dentistry. GA has been shown to have an adverse effect on electrolyte balance and vitamin D in mice, and to cause hypersensitivity in humans. More studies are needed before the pharmacological properties of GA can be utilized in therapy.

Long-term exercise training and angiotensin-converting enzyme inhibition differentially enhance myocardial capillarization in the spontaneously hypertensive rat.

OBJECTIVES: To investigate whether combined treatment with lisinopril, an angiotensin-converting enzyme (ACE) inhibitor and exercise training would have an additive effect in enhancing the capillary supply of the left ventricular (LV) myocardium in spontaneously hypertensive rats (SHR). DESIGN: Twelve-week-old male SHR were divided into four groups (10-12 each): sedentary, sedentary treated with lisinopril (15-20 mg/kg per day by gavage), exercise trained, and exercise trained while treated with lisinopril. Exercise training consisted of 1 h a day/5 days a week of running on a treadmill. METHODS: After 10 weeks of experimental protocols, capillary surface density and length density were sterologically determined in 1 mum thick LV tissue samples from perfuse-fixed hearts. RESULTS: Lisinopril significantly reduced systolic blood pressure (SBP) and LV mass in the sedentary with lisinopril and exercise trained with lisinopril groups but did not affect the heart rate (HR). Exercise training did not reduce SBP or LV mass, but significantly reduced HR in the exercise trained and exercise trained with lisinopril groups. Lisinopril treatment (sedentary with lisinopril), exercise training (exercise) and their combination (exercise trained with lisinopril) significantly increased myocardial capillary surface area density by 26, 38 and 65% and length density by 38, 48 and 67%, respectively. CONCLUSION: Lisinopril administration and exercise training independently enhanced myocardial capillarization through a reduction of myocardial mass and stimulation of angiogenesis, respectively. A combination of the two treatments enhanced myocardial capillarization more than either intervention alone. This may aid in the restoration of the normal nutritional status of cardiac myocytes compromised by the hypertrophic state of hypertension.