Acute cardiovascular effects of tacrolimus in the isolated guinea pig heart

Effects of dandelion root on rat heart function and oxidative status

This study aimed to examine the effects of dandelion root on rat heart function and oxidative status. At the beginning of the experimental protocol, Wistar albino rats were randomly classified into two groups (10 rats per group): 1. control group - animals that drank tap water; 2. experimental group - animals that drank dandelion root for four weeks. Every morning for four weeks, the animals received freshly boiled dandelion root in a volume of 250 ml. At the end of the dandelion administration, animals were sacrificed, and their hearts were isolated and retrogradely perfused according to the Langendorff technique at a gradually increasing perfusion pressure between 40 - 120 cm H₂O. The following myocardial function parameters were measured: maximum rate of left ventricular pressure development (dp/dt max), minimum rate of left ventricular pressure development (dp/dt min), systolic left ventricular pressure (SLVP), diastolic left ventricular pressure (DLVP), heart rate (HR). In addition, the coronary flow (CF) was measured flowmetrically. Finally, blood samples were collected after sacrificing to determine oxidative stress biomarkers: nitrite (NO₂^-), superoxide anion radical (O₂^-), hydrogen peroxide (H₂O₂), the index of lipid peroxidation (TBARS), reduced glutathione (GSH), catalase (CAT) and superoxide dismutase (SOD). The present pioneer results indicated that dandelion root did not manifest a negative impact on functional aspects of isolated rat heart. In addition, dandelion consumption was not associated with promising results in terms of maintaining systemic redox balance.

Calcineurin-independent inhibition of KV1.3 by FK-506 (tacrolimus): a novel pharmacological property

The interaction of FK-506 with KV1.3, stably expressed in Chinese hamster ovary cells, was investigated with the whole cell patch-clamp technique. FK-506 inhibited KV1.3 in a reversible, concentration-dependent manner with an IC50of 5.6 μM. Rapamycin, another immunosuppressant, produced effects that were similar to those of FK-506 (IC50= 6.7 μM). Other calcineurin inhibitors (cypermethrin or calcineurin autoinhibitory peptide) alone had no effect on the amplitude or kinetics of KV1.3. In addition, the inhibitory action of FK-506 continued, even after the inhibition of calcineurin activity. The inhibition produced by FK-506 was voltage dependent, increasing in the voltage range for channel activation. At potentials positive to 0 mV (where maximal conductance is reached), however, no voltage-dependent inhibition was found. FK-506 exhibited a strong use-dependent inhibition of KV1.3. FK-506 shifted the steady-state inactivation curves of KV1.3 in the hyperpolarizing direction in a concentration-dependent manner. The apparent dissociation constant for FK-506 to inhibit KV1.3 in the inactivated state was estimated from the concentration-dependent shift in the steady-state inactivation curve and was calculated to be 0.37 μM. Moreover, the rate of recovery from inactivation of KV1.3 was decreased. In inside-out patches, FK-506 not only reduced the current amplitude but also accelerated the rate of inactivation during depolarization. FK-506 also inhibited KV1.5 and KV4.3 in a concentration-dependent manner with IC50of 4.6 and 53.9 μM, respectively. The present results indicate that FK-506 inhibits KV1.3 directly and that this effect is not mediated via the inhibition of the phosphatase activity of calcineurin.