The acute diuretic effects with low-doses of natural prenylated xanthones in rats

Characterization of Diclofenac-induced Renal Damage in Normotensive and Hypertensive Rats: A Comparative Analysis

BACKGROUND

Diclofenac is the non-steroidal anti-inflammatory drug (NSAID) mostly prescribed worldwide, but it is highly associated with hypertension and acute kidney injury. Despite that, little information is available about the renal effects of diclofenac in hypertensive individuals, which led us to carry out this comparative study between the renal effects of this NSAID in normotensive (NTR) and spontaneously hypertensive rats (SHR).

METHODS

Male Wistar NTR and SHR were orally treated with vehicle (V: 10 mL/kg) or diclofenac sodium (D: 100 mg/kg) once a day for 3 days. Urine volume, electrolytes excretion (Na+, K+, Cl-, and Ca2+), urea, creatinine, pH, and osmolarity were evaluated. Furthermore, blood samples and renal tissue were collected to perform biochemical and histological analysis.

RESULTS

Diclofenac increased the renal corpuscle and bowman's space in the SHR, while no microscopic changes were observed in the renal tissue of NTR. Regarding the urinary parameters, diclofenac reduced urine volume, pH, osmolarity, and all electrolytes excretion, followed by decreased urea and creatinine levels in both lineages. Moreover, it also induced hyponatremia, hypokalemia, and hypocalcemia in SHR, while reduced glutathione-S-transferase activity, lipid hydroperoxides, and nitrite levels in renal tissue.

CONCLUSIONS

The data presented herein demonstrated that diclofenac induces renal damage and impaired renal function in both NTR and SHR, but those effects are exacerbated in SHR, as seen by the histological changes and electrolytes balance disturbance, therefore, reinforcing that diclofenac may increase the risks of cardiovascular events in hypertensive patients.

Vasodilation and Blood Pressure-Lowering Effect of 3-Demethyl-2-Geranyl-4-Prenylbellidifoline, a Xanthone Obtained from Garcinia achachairu, in Hypertensive Rats

3-demethyl-2-geranyl-4-prenylbellidifoline (DGP), a natural xanthone isolated from Garcinia achachairu, has previously demonstrated remarkable diuretic and renal protective actions. The present study expands its actions on the cardiovascular system by evaluating its vasorelaxant and blood pressure-lowering effects in spontaneously hypertensive rats (SHRs). Aortic endothelium-intact (E+) preparations of SHRs pre-contracted by phenylephrine and exposed to cumulative concentrations of G. achachairu extract, fractions, and DGP exhibited a significant relaxation compared to vehicle-only exposed rings. The non-selective muscarinic receptor antagonist (atropine), the non-selective inhibitor of nitric oxide synthase (L-NAME), as well as the inhibitor of soluble guanylate cyclase (ODQ) altogether avoided DGP-induced relaxation. Tetraethylammonium (small conductance Ca2+-activated K+ channel blocker), 4-aminopyridine (a voltage-dependent K+ channel blocker), and barium chloride (an influx-rectifying K+ channel blocker) significantly reduced DGP capacity to induce relaxation without the interference of glibenclamide (an ATP-sensitive inward rectifier 6.1 and 6.2 K+ channel blocker). Additionally, administration of DGP, 1 mg/kg i.v., decreased the mean, systolic, and diastolic arterial pressures, and the heart rate of SHRs. The natural xanthone DGP showed promising potential as an endothelium-dependent vasorelaxant, operating through the nitric oxide pathway and potassium channels, ultimately significantly reducing blood pressure in hypertensive rats.

Diuretic, Natriuretic, And Ca2+-Sparing Effect Of The Alkaloid Boldine In Rats

BACKGROUND

Previous studies indicate the renal vasodilating effects of boldine, an alkaloid found in Peumus boldus. However, its potential to induce diuresis still needs to be studied.

METHODS

Wistar rats were used and the urine volume was noted for 8 h and further studied.

RESULTS

The acute treatment at 0.1 and 0.3 mg/kg of boldine showed a diuretic, natriuretic, and Ca2+-sparing effect in rats without changing the urinary elimination of K+and Cl-. When boldine was given in combination with hydrochlorothiazide, there was an increase in urinary volume compared to the vehicle group. However, this was not different from the treatments in its isolated form. Urine Ca2+values ​​remained low but were not enhanced by this association. The excretion of Na+and Cl- was significantly increased compared to the group that received only vehicle or boldine. On the other hand, although the association of amiloride plus boldine did not result in a diuretic effect, the increase in Na+and the reduction in K+excretion were significantly potentiated. Furthermore, in the presence of the non-selective muscarinic receptor antagonist atropine, boldine showed reduced capacity to increase urinary volume, maintaining the natriuretic and Ca2+-sparing effect, besides a very evident K+-sparing action. Similar results were obtained in the presence of the non-selective cyclooxygenase inhibitor indomethacin. Furthermore, boldine showed an ex vivo antiurolithiasis activity, reducing calcium oxalate's precipitation and crystallization.

CONCLUSIONS

This study reveals the diuretic, natriuretic, Ca2+-sparing, and antiurolithiatic effects of boldine, an action possibly related to muscarinic receptor activation and prostanoid generation.

Diuretic and Natriuretic Effects of Hesperidin, a Flavanone Glycoside, in Female and Male Hypertensive Rats

Hesperidin (HSP) is a major flavanone glycoside in citrus fruits, including sweet oranges and lemons. It demonstrates numerous pharmacological activities, such as antihypertensive effects and cardiac and kidney tissue protection. However, its effect on modulating renal function has yet to be properly explored. Female and male Wistar spontaneously hypertensive rats (SHR) were used to test the effect of HSP on renal function. The rats were divided into different groups, treated orally, and placed in metabolic cages for urine collection for 8 h. HSP, at doses of 0.3-3 mg/kg, led to an increase in urine volume in both female and male SHR. This effect was associated with increased Na⁺ elimination (3 mg/kg) without causing any change in K⁺ excretion or pH and conductivity values. When given HSP in combination with hydrochlorothiazide (HCTZ) or amiloride (AMLR), urine volume and Na⁺ elimination were significantly increased compared to the group that received only HSP. In relation to K⁺ excretion, the depleting effect of HCTZ and the sparing of AMLR prevailed in both groups. Pre-treatment with a non-selective cholinergic receptor antagonist, atropine, partially prevented HSP-induced diuresis and natriuresis in male SHR, but this effect was not demonstrated with the non-selective inhibitor of the enzyme cyclooxygenase, indomethacin. This study shows the diuretic action of HSP in hypertensive rats, an activity probably associated with the cholinergic pathway. Although various biological actions have already been defined for HSP, this pioneering research reveals its potential as a diuretic medicine.

Diuretic and antiurolithic effect of Garcinia humilis (Vahl) C.D.Adams leaves, a medicinal plant native to South American countries

This study evaluated the diuretic and antiurolithic effect of methanolic extract (MEGHL), dichloromethane (DCM), and ethyl acetate (EtA) fractions obtained from the leaves of Garcinia humilis , a medicinal plant known as achachairu and native to South American countries such as Bolivia, Peru, and Brazil. For the analysis of diuretic effect, the female rats received the treatment with MEGHL (3, 10, and 30 mg/kg), DCM (1, 3 and 10 mg/kg), EtA (1, 3, and 10 mg/kg), hydrochlorothiazide (HCTZ; 10 mg/kg), or vehicle (VEH) after an overload of saline solution. At the end 8-h of the experiment, the urinary parameters were measured . Additionally, the antiurolithic effect was analyzed, in which sodium oxalate was added in synthetic urine in the presence or absence of MEGHL, DCM, and EtA in different concentrations (0.1, 0.3, and 1 mg/mL). MEGHL, DCM, and EtA were able to promote 8-h diuresis in rats. MEGHL treatment at dose 30 mg/kg was accompanied by increased urinary Na + , K + and Cl - excretion. Moreover, the DCM and EtA fractions treatment increased K + and Cl - excretion in the urine, although it does not cause any change in Na + elimination. All the preparations were able to exert an antiurolithic effect in vitro , decreasing the number of calcium oxalate crystals of the monohydrate and dihydrate types. Taking together, the results presented herein showed that the preparations of G. humilis leaves are promising strategies to induce diuresis and antiurolithic effects.

Boldine, an Alkaloid from Peumus boldus Molina, Induces Endothelium-Dependent Vasodilation in the Perfused Rat Kidney: Involvement of Nitric Oxide and Small-Conductance Ca2+-Activated K+ Channel

Boldine, 2,9-dihydroxy-1,10-dimethoxyaporphine, is the main alkaloid found in the leaves and bark of Peumus boldus Molina. In recent years, boldine has demonstrated several pharmacological properties that benefit endothelial function, blood pressure control, and reduce damage in kidney diseases. However, the renal vasodilator effects and mechanisms remain unknown. Herein, perfused rat kidneys were used to study the ability of boldine to induce vasodilation of renal arteries. For that, left kidney preparations with and without functional endothelium were contracted with phenylephrine and received 10–300 nmol boldine injections. The preparations were then perfused for 15 min with phenylephrine plus L-NAME, indomethacin, KCl, tetraethylammonium, glibenclamide, apamin, charybdotoxin, or iberiotoxin. In 30, 100, and 300 nmol doses, boldine induced a dose-and endothelium-dependent relaxing effect on the renal vascular bed. No vasodilator effects were observed in preparations lacking functional endothelium. While the inhibition of the cyclooxygenase enzyme through the addition of indomethacin did not cause any change in the vasodilating action of boldine, the nonselective nitric oxide synthase inhibitor L-NAME fully precluded the vasodilatory action of boldine at all doses tested. The perfusion with KCl or tetraethylammonium (nonselective K⁺ channels blocker) also abolished the vasodilatory effect of boldine, indicating the participation of K⁺ channels in the renal action of boldine. The perfusion with glibenclamide (selective ATP-sensitive K⁺ channels blocker), iberiotoxin (selective high-conductance Ca²⁺-activated K⁺ channel blocker), and charybdotoxin (selective high- and intermediate-conductance Ca²⁺-activated K⁺ channel blocker) did not modify the vasodilatory action of boldine. On the other hand, the perfusion with apamin (selective small-conductance Ca²⁺-activated K⁺ channel blocker) completely prevented the vasodilatory action of boldine at all doses tested. Together, the present study showed the renal vasodilatory properties of boldine, an effect dependent on the generation of nitric oxide and the opening of a small-conductance Ca²⁺-activated K⁺ channel.

Prolonged Diuretic and Renoprotective Effects of a Xanthone Obtained from Garcinia achachairu Rusby in Normotensive and Hypertensive Rats

The previous study showed that 1,5,8-trihydroxy-4',5'-dimethyl-2H-pyrano(2,3 : 3,2)-4-(3-methylbut-2-enyl) xanthone (TDP) obtained from Garcinia achachairu Rusby (Clusiaceae) branches induces acute diuresis in normotensive (NTR) and spontaneously hypertensive rats (SHR) after 8 h of the experiment. In complementarity, the present study evaluated the prolonged diuretic and renoprotective effects of TDP in both NTR and SHR. The animals received, once a day, oral treatment with TDP (0.1 mg/kg), hydrochlorothiazide (10 mg/kg), or vehicle (VEH; 10 mL/kg). At the end of 7 days, the urine, blood, and kidney samples were collected for biochemical and histological analyzes. The urinary volume of both NTR and SHR after 7 days of treatment with the TDP was significantly increased, associated with augmented urinary electrolyte excretion levels. The treatments did not modify the urinary pH values nor the parameters analyzed in plasma (Na⁺, K⁺, Cl^-, and Ca²⁺). Concerning the renal analyzes, when compared with the VEH-treated NTR group, while the activity of the enzymes catalase (CAT) and N-acetyl-β-D-glucosaminidase (NAG), as well as nitrite levels, were increased, the generation of lipid hydroperoxides and the activity of the enzyme myeloperoxidase (MPO) were unaltered. On the other hand, the activities of superoxide dismutase (SOD) and glutathione S-transferase (GST) and the levels of reduced glutathione (GSH) in kidney homogenates of the SHR group were decreased. However, TDP augmented the levels of GSH and GST activities and reduced the levels of nitrite and the activities of CAT and MPO, when compared with VEH-treated only SHR. Besides, the treatment with TDP alleviated the morphological changes of the renal corpuscle region of SHR. Together, these results revealed the prolonged diuretic effect of TDP and their renal protective effect by improving the antioxidative capacity.