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The aim of this study was to determine the concentrations of nickel and cadmium in blood plasma of the people exposed to cement dust emissions and to investigate the effects of exposure period on the activities of Na+/K+ ATPase enzymes in their erythrocyte membranes. The study was carried out on people living in Eskişehir Cukurhisar rural area, located near a cement factory. Blood samples of the individuals residing in this area were taken from 80 subjects (30 for control) following a physical examination. The analysis of plasma samples showed that nickel concentrations in subject group were found to be significantly higher than those of the control group (p < 0.001). Cadmium concentrations were found to be within the reference values for both group and no difference was found between the subjects and controls (p > 0.05). Furthermore, no correlation was observed between the levels of Na+/K+ ATPase activity in erythrocyte membranes of the subject group and the ages of people living in the region (p > 0.05, r = 0.133). It was also observed that nickel concentrations increased by age (p < 0.001, r = 0.646) while no effect was observed in means of cadmium. Na+/K+ ATPase activities in the erythrocyte membranes were not affected. In conclusion although there was no difference between the Na+/K+ ATPase activity in means of age, there was an environmental pollution and may be it was due to the industrial plant.

Preference for the Northern (N) ring conformation of the ribose moiety of nucleotide 5'-triphosphate agonists at P2Y(1), P2Y(2), P2Y(4), and P2Y(11) receptors, but not P2Y(6) receptors, was established using a ring-constrained methanocarba (a 3.1.0-bicyclohexane) ring as a ribose substitute (Kim et al. J. Med. Chem. 2002, 45, 208-218.). We have now combined the ring-constrained (N)-methanocarba modification of adenine nucleotides with other functionalities known to enhance potency at P2 receptors. The potency of the newly synthesized analogues was determined in the stimulation of phospholipase C through activation of turkey erythrocyte P2Y(1) or human P2Y(1) and P2Y(2) receptors stably expressed in astrocytoma cells. An (N)-methanocarba-2-methylthio-ADP analogue displayed an EC(50) at the hP2Y(1) receptor of 0.40 nM and was 55-fold more potent than the corresponding triphosphate and 16-fold more potent than the riboside 5'-diphosphate. 2-Cl-(N)-methanocarba-ATP and its N(6)-Me analogue were also highly selective, full agonists at P2Y(1) receptors. The (N)-methanocarba-2-methylthio and 2-chloromonophosphate analogues were full agonists exhibiting micromolar potency at P2Y(1) receptors, while the corresponding ribosides were inactive. Although beta,gamma-methylene-ATP was inactive at P2Y receptors, beta,gamma-methylene-(N)-methanocarba-ATP was a potent hP2Y(1) receptor agonist with an EC(50) of 160 nM and was selective versus hP2Y(2) and hP2Y(4) receptors. The rates of hydrolysis of Northern (N) and Southern (S) methanocarba analogues of AMP by rat 5'-ectonucleotidase were negligible. The rates of hydrolysis of the corresponding triphosphates by recombinant rat NTPDase1 and 2 were studied. Both isomers were hydrolyzed by NTPDase 1 at about half the rate of ATP hydrolysis. The (N) isomer was hardly hydrolyzed by NTPDase 2, while the (S) isomer was hydrolyzed at one-third of the rate of ATP hydrolysis. This suggests that new, more stable and selective nucleotide agonists may be designed on the basis of the (N)-conformation, which greatly enhanced potency at P2Y(1) receptors.

The effect of nucleoside diphosphate kinase (NDPK) on the activity of guanine nucleotide regulatory protein (G-protein) mediated phospholipase C (PLC) and on the [35S] GTPT tau S binding of G-protein was investigated in this work in order to demonstrate the mechanism behind the regulation of G-protein and its effector PLC by NDPK. The stimulation of PLC in turkey erythrocyte membrane by both GTP and GTP tau S indicated that the PLC stimulation was mediated by G-protein. NDPK alone stimulated PLC activity, as well as the stimulation in the presence of GTP and GDP, in a dose-dependent manner. However, NDPK inhibited GTP tau S-stimulated PLC. Furthermore, NDPK inhibited [35S]GTP tau S binding of purified Gi-protein in a non-competitive manner. A hypothesis implying an important role of direct interaction of G-protein and NDPK in the regulation of their functions is suggested and discussed.