Blood pressure regulates the activity and function of the Na-K-2Cl cotransporter in vascular smooth muscle

The Na-K-2Cl cotransporter (NKCC1) is one of several transporters that have been linked to hypertension, and its inhibition reduces vascular smooth muscle tone and blood pressure. NKCC1 in the rat aorta is stimulated by vasoconstrictors and inhibited by nitrovasodilators, and this is linked to the contractile state of the smooth muscle. To determine whether blood pressure also regulates NKCC1, we examined the acute effect of hypertension on NKCC1 in rats after aortic coarctation. In the hypertensive aorta (28-mmHg rise in mean blood pressure), an increase in NKCC1 activity (measured as bumetanide-sensitive (86)Rb efflux) was apparent by 16 h and reached a plateau of 62% greater than control at 48 h. In contrast, there was a slight decrease in NKCC1 activity in the hypotensive aorta (21% decrease in mean blood pressure). Measurement of NKCC1 mRNA by real-time PCR revealed a fivefold increase in the hypertensive aorta compared with the hypotensive aorta or sham aorta. The inhibition by bumetanide of isometric force response to phenylephrine was significantly greater in the hypertensive aorta than in the control aorta or hypotensive aorta. We conclude that NKCC1 in rat aortic smooth muscle is regulated by blood pressure, most likely through changes in transporter abundance. This upregulation of NKCC1 is associated with a greater contribution to force generation in the hypertensive aorta. This is the first demonstration that NKCC1 in vascular smooth muscle is regulated by blood pressure and indicates that this transporter is important in the acute response of vascular smooth muscle to hypertension.     

Trace element concentrations and superoxide dismutase and catalase activities in benign and malignant larynx tumors

The plasma and erythrocyte levels of zinc, copper, and magnesium and the activities of red-cell copper-zinc superoxide dismutase (Cu/Zn-SOD) and catalase (CAT) were determined in patients with benign and malignant tumors of the larynx. Blood samples from patients and healthy controls were drawn using heparinized tubes. The erythrocyte Cu/Zn-SOD and CAT activities were determined spectrophotometrically and the zinc, copper, and magnesium concentrations were determined in erythrocyte and plasma by atomic absorption spectrometry. Variance analysis was employed in the statistical evaluation of the findings. There was a significant increase in red-cell Cu/Zn-SOD activity in the subjects with malignant and benign tumors compared to controls (p<0.001). The CAT activity increased only in the benign tumor group (p<0.01). The plasma zinc concentrations were significantly lower in the malignant tumor group (p<0.05) and significantly higher in the benign tumor group (p<0.01). The erythrocyte copper concentrations were significantly lower in both benign and malignant tumor groups (p<0.001). The plasma copper and magnesium and the erythrocyte magnesium concentrations did not show significant differences relative to controls (p>0.05). The increases in the activities of SOD and CAT activities and the changes in trace elements concentrations can indicate the presence of increased reactive oxygen species that might play a part in the pathogenesis larynx tumors. Presented at the IX Asian-Pacific Congress of Clinical Biochemistry, March 9–14, 2002, New Delhi, India.     

Synthesis, antimicrobial activity and conformational analysis of novel substituted pyridines: BF(3)-promoted reaction of hydrazine with 2-alkoxy pyridines

Some new 2-alkoxy-3-cyano-4,6-diarylpyridines 3,4 were synthesized by condensation of different alpha,beta-unsaturated ketones 1 with malononitrile 2, followed by cyclization in sodium alkoxide/alcohol system. Lewis acid-catalyzed reaction of 4 with hydrazine afforded the corresponding 1H-pyrazolo[3,4-b]pyridines 5. The potency of the results as antimicrobial agents has been evaluated. The structure of the newly prepared compounds was assessed by microanalysis, IR and NMR spectra. Molecular mechanics (MM2) and semiemperical (AM1) molecular orbital calculations have been performed for the most biologically active compounds 5b and c to get insight into their molecular structures and to learn more about their stable molecular conformations.     

Identification of PDZ5, a candidate universal minicircle sequence binding protein of Trypanosoma cruzi

The dodecamer universal minicircle sequence is a conserved sequence present in minicircles of trypanosomatid kinetoplast DNA studied so far. This sequence is recognised by a protein named universal minicircle sequence binding protein, described for Crithidia fasciculata, involved in minicircle DNA replication. We have identified a Trypanosoma cruzi gene homologue of the Crithidia fasciculata universal minicircle sequence binding protein. Similar to the Crithidia fasciculata universal minicircle sequence binding protein, the Trypanosoma cruzi protein, named PDZ5, contains five zinc finger motifs. Pulsed field gel electrophoresis indicated that the pdz5 gene is located in the chromosomal band XX of the Trypanosoma cruzi genome. The predicted amino acid sequence of PDZ5 shows a high degree of similarity with several trypanosomatid zinc finger proteins. Specific antibody raised against Crithidia fasciculata universal minicircle sequence binding protein recognises both the recombinant and endogenous PDZ5. The complete pdz5 coding sequence cloned in bacteria expresses a recombinant PDZ5 protein that binds specifically to the universal minicircle sequence dodecamer. These data strongly suggest that PDZ5 represents a Trypanosoma cruzi universal minicircle sequence binding protein.     

A comparative study on effect of dietary selenium and vitamin E on some antioxidant enzyme activities of liver and brain tissues

Since selenium and vitamin E have been increasingly recognized as an essential element in biology and medicine, current research activities in the field of human medicine and nutrition are devoted to the possibilities of using these antioxidants for the prevention or treatment of many diseases. The present study was aimed at investigating and comparing the effects of dietary antioxidants on glutathione reductase and glutathione peroxidase activities as well as free and protein-bound sulfhydryl contents of rat liver and brain tissues. For 12–14 wk, both sex of weanling rats were fed a standardized selenium-deficient and vitamin E-deficient diet, a selenium-excess diet, or a control diet. It is observed that glutathione reductase and glutathione peroxidase activities of both tissues of the rats fed with a selenium-deficient or excess diet were significantly lower than the values of the control group. It is also shown that free and bound sulfhydryl concentrations of these tissues of both experimental groups were significantly lower than the control group. The percentage of glutathione reductase and glutathione peroxidase activities of the deficient group with respect to the control were 50% and 47% in liver and 66% and 61% in the brain, respectively; while these values in excess group were 51% and 69% in liver and 55% and 80% in brain, respectively. Free sulfhydryl contents of the tissues in both experimental groups showed a parallel decrease. Furthermore, the decrease in protein-bound sulfhydryl values of brain tissues were more pronounced than the values found for liver. It seems that not only liver but also the brain is an important target organ to the alteration in antioxidant system through either a deficiency of both selenium and vitamin E or an excess of selenium alone in the diet.     

Adenosine triphosphate alters the selenite-induced contracture and negative inotropic effect on cardiac muscle contractions

Selenium is known to play an important role in the physiology of many different cell types and extracellular application of selenite causes cellular dysfunction in many different types of tissues. In a previous study, we have shown that in rat ventricles, sodium selenite (≥1 mM) caused an increase in the resting tension and a decrease in contractile force, in a time-dependent manner. In the present study, we have shown that sodium selenite caused a contracture state both in Langendorff perfused hearts and isolated papillary muscles. We also showed that the application of extracellular ATP (0.1 mM) markedly reduced this detrimental effect of sodium selenite on ventricular contraction in Langendorff perfused hearts and delayed it in isolated papillary muscle preparations. In contrast, isoproterenol (0.1 μM) did not seem to influence this action of sodium selenite in papillary muscle preparations. Possible reasons for this protective effect of ATP to selenite-induced contracture are also discussed.     

The effects of dietary chromium supplementation on some blood parameters in sheep

The effects of dietary inorganic chromium on some biochemical parameters were determined in lambs fed either a control diet or a 200-ppb or 400-ppb chromium-supplemented diet. The live weight of the animals were measured and jugular blood samples were collected prior to supplementation (d 0) and on d 20, 40, and 55. On d 55, three animals from each group were slaughtered to measure subcutaneous fat. Sera were analyzed for glucose, triglyceride, total cholesterol, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol, total protein, albumin, ALT, AST, and GGT levels. Chromium supplementation had no significant effect on live weight, but subcutaneous fat was reduced significantly in both chromium groups. There was a slight decrease in glucose concentrations in the 200-ppb chromium group, although only the differences on d 55 were significant. Triglyceride levels in both chromium groups were lower than the control group with marked differences in the 400-ppb chromium group. HDL cholesterol levels increased in both treatment groups compare to control, although the differences in the 400-ppb chromium group on d 40 were significant. Serum Cr concentrations slightly but not significantly increased in both chromium groups. No significant differences were found in total and LDL cholesterol, total protein, albumin, ALT, AST, and GGT levels. In conclusion, chromium supplementation may affect carbohydrate and lipid metabolisms and lipid deposition in lambs.     

Zinc-induced changes in ionic currents of cardiomyocytes

The whole-cell voltage-clamp technique was applied to isolated ventricular myocytes to investigate the effects of extracellular and intracellular zinc application on L-type Ca²⁺ channel currents (I _Ca). Extracellular zinc exposure at micromolar concentration induced a reversible (with washout of ZnCl₂) reduction (30%) of I _Ca with no change in current-voltage relationship. On the other hand, an increase of intracellular free-zinc concentration, [Zn²⁺]_i, from normal (less than 1 nM) to approx 7 nM with 10 μM Zn-pyrithione exposure caused an inhibition of 33±6% in the peak of the I _Ca and altered the voltage dependency of L-type Ca²⁺ channels with a 10-mV left shift and a hump at around −40 mV in its current-voltage relation. In contrast, N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) strongly inhibited the I _Ca (42±2%), with only a small but detectable outward shift of the holding current measured at the end of the pulses. Zn-pyrithione and TPEN caused a reproducible decrease of the I _Ca. Interestingly, TPEN application, without Zn-pyrithione pretreatment, inhibited the I _Ca (35±2%) with no change in voltage dependency. Taken together, the results suggest that both extracellular and intracellular zinc increases under pathological conditions in cardiomyocytes can alter the I _Ca, but their effects are not in the same order and same manner. One should consider these possible side effects when it is suggested to be vital to cardiovascular cell integrity and functions.