Effects of Nigella sativa supplementation for one month on cardiac reserve in rats.

Nigella sativa (N. sativa) has a long history of use in folk medicine. In a current study performed in this laboratory, two-month dietary supplementation with N. sativa extract to normal rats has shown a homogenous cardiac hypertrophy and enhanced cardiac contractility at baseline conditions. In the present study, shorter (one-month) duration of oral N. sativa administration was adopted to detect possible earlier cardiac responses. In addition, in vitro cardiac stress by the beta adrenoceptor agonist isoproterenol was used to assess the intrinsic cardiac reserve mechanisms. The hearts of Nigella-treated rats developed a moderate but significant hypertrophy that was evident by an increase in the heart weight to body weight ratio. The observed Nigella-induced cardiac hypertrophy was associated with an increase in the baseline cardiac inotropic properties as well as the maximal peak tension generation upon progressive cardiac stress by isoproterenol infusion. The demonstrated selective enhancement of the inotropic reserve favours the physiological nature of Nigella-induced cardiac hypertrophy, similar to that provoked by exercise training.

Blockade of Na+/H+ exchanger contracts the portal vein of spontaneously hypertensive and Wistar Kyoto rats.

It has been claimed that the activity of Na+/H+ exchanger (NHE) is altered in spontaneously hypertensive rats (SHR) suggesting a possible role for it in the pathophysiology of hypertension. The purpose of this study has been to investigate the effect of blockade of NHE on the noradrenaline (NA) and 26K+ induced tone and on the recovery of tone from acid induced contractions in the portan vein of spontaneously hypertensive rats (SHR) as compared to their controls of Wistar Kyoto rats (WKY). Blockade of NHE by 10(-4) dimethylamiloride (DMA) raised the tone of NA and 26K+ activated preparation of both strains, the contractions being higher with NA activation. Total blockade of NHE by replacement of Na in solution with N-methy-D-Glucamine (NMDG) raised the tone of the NA activated preparations by 45+/-10%, n=8, P<0.01 and 33+/-4%, n=12, P < 0.01 in SHR and WKY respectively. The time for 50% relaxation from NH4Cl washout contraction was significantly prolonged by 10(-5) and 10(-4) M DMA in both strains under NA or 26K+ activation. DMA effect was greater on NA than on 26K+ activated preparations, and was not significantly different when comparing SHR to WKY results. In conclusion the results reported in this study indicate that NHE has similar activity in WKY and SHR portal veins and that its blockade contracts both preparations. Therefore, it is unlikely that increased NHE activity, acting directly on vascular smooth muscle tone, could be a primary cause for hypertension.

Response of the portal vein of spontaneous hypertensive rats to intracellular pH.

The effect of intracellular pH perturbations on the portal vein preparations of spontaneously hypertensive rats and their control Wistar Kyoto rats was investigated. Intracellular alkalinity induced by application of 20 mM NH4Cl or 20 mM trimethylamine produced dilatation of both preparations. Intracellular acidity induced by washout of the previous ammonium and trimethylamine solutions or by application of 20 mM sodium propionate solution caused constriction of both preparations. These responses of the portal veins of both animals to intracellular pH variations were qualitatively the same in nonactivated preparations and in preparations precontracted with 26 mM K+ or 1 microM norepinephrine. Recovery from acidic constrictions induced by washout of ammonium and trimethylamine solutions was significantly slower in spontaneous hypertensive rats than in Wistar Kyoto rats preparations. Conceivably, a lower intracellular pH in the vascular smooth muscle of the resistance vessels of hypertensive patients, as compared to normotensive individuals, may partly account for the hypertensive phenomena.