Decreased osteocalcin levels in patients with chronic obstructive pulmonary disease using long-term inhaled beclomethasone dipropionate.

Inhaled corticosteroids have been used in the treatment of chronic obstructive pulmonary disease (COPD) for many years. However the adverse effects of corticosteroids on bone formation may require special consideration in these patients. This study was undertaken to investigate the effects of long-term inhaled beclomethasone dipropionate treatment on the biochemical markers of bone formation. For this purpose, serum osteocalcin, alkaline phosphatase, free calcium, and inorganic phosphate levels were measured in 65 male COPD patients. Patients in the control group (n = 30) had not taken oral or inhaled corticosteroids for at least 1 year. Only those patients using beclomethasone with metered-dose inhalers were included in the treatment group (n = 35). The mean age of the control group was 61.63 +/- 1.84 (mean +/- SEM). In the treatment group, the mean age was 59.10 +/- 2.29 and patients in this group had taken beclomethasone for an average time of 23.94 +/- 2.72 months (for at least 12 months) at an average concentration of 1,142.0 +/- 79.64 microg/d. The mean serum osteocalcin levels in the control group and treatment group were 7.03 +/- 0.19 ng/mL and 3.74 +/- 0.12 ng/mL, respectively. Comparison of values between groups indicates that serum osteocalcin levels in patients using beclomethasone were significantly lower than that of patients in the control group. Serum alkaline phosphatase levels were 167.96 +/- 1.49 U/L and 168.17 +/- 1.60 U/L for the control and treatment groups, respectively. There was no statistically significant difference among these values (Student's t test; P >.05). The mean values of total serum calcium and inorganic phosphate were not statistically different between the groups (P >.05). These results indicate that long-term inhaled beclomethasone treatment in COPD patients may induce significant changes in osteocalcin levels and require close monitoring for osteoporotic changes.

Direct inhibition of voltage-dependent Ca(2+) fluxes by ethanol and higher alcohols in rabbit T-tubule membranes.

The effects of ethanol and higher alcohols on 45Ca(2+) fluxes, mediated by voltage-dependent Ca(2+) channels (VDCCs), were investigated in inside-out transverse (T)-tubule membrane vesicles from rabbit skeletal muscle. 45Ca(2+) effluxes were induced by membrane potentials generated via establishing K(+) gradients across the vesicles, and were significantly inhibited by the inorganic Ca(2+) channel blocker La(3+) (1 mM) and the Ca(2+) channel antagonist nifedipine (1-10 microM). Ethanol, in the concentration range of 100-400 mM, caused a significant suppression of depolarization-induced 45Ca(2+) fluxes. Ethanol also functionally modulated the effect of nifedipine (1-10 microM) and the Ca(2+) channel agonist Bay K 8644 (1 microM) on Ca(2+) effluxes. Pretreatment with pertussis toxin (5 microg/ml) or phorbol 12-myrstate 13-acetate (PMA, 50 nM) did not affect the ethanol inhibition of 45Ca(2+) fluxes. Further experiments with alcohols revealed that butanol, hexanol, octanol and decanol also significantly inhibited 45Ca(2+) effluxes. However, undecanol and dodecanol did not cause any significant change on 45Ca(2+) fluxes, indicating that the effects of alcohols on 45Ca(2+) effluxes exhibit a cut-off phenomenon. In radioligand binding studies, it was found that at the concentrations used in flux studies, alcohols did not alter the characteristics of the specific binding of [3H]PN 200-110 to T-tubule membranes. Results indicate that ethanol directly inhibits the function of voltage-dependent Ca(2+) channels without modulating the specific binding of Ca(2+) channel ligands of the dihydropyridine class, and that this inhibition is independent of intracellular Ca(2+) levels.

Endogenous cannabinoid anandamide directly inhibits voltage-dependent Ca(2+) fluxes in rabbit T-tubule membranes.

The effect of the endogenous cannabinoid, anandamide on Ca(2+) flux responses mediated by voltage-dependent Ca(2+) channels was studied in transverse tubule membrane vesicles from rabbit skeletal muscle. Vesicles were loaded with 45Ca(2+) and membrane potentials were generated by establishing K(+) gradients across the vesicle using the ionophore, valinomycin. Anandamide, in the range of 1-100 microM, inhibited depolarization-induced efflux responses. Anandamide also functionally modulated the effects of nifedipine (1-10 microM) and Bay K 8644 (1 microM) on Ca(2+) flux responses. Pretreatment with the specific cannabinoid receptor antagonist, SR141716A (1 microM), pertussis toxin (5 microg/ml), the amidohydrolase inhibitor, phenylmethylsulfonyl fluoride (0.2 mM) or the cyclooxygenase inhibitor, indomethacin (5 microM) did not alter the inhibition of efflux responses by anandamide. Arachidonic acid (10-100 microM) also effectively inhibited 45Ca(2+) efflux from membrane vesicles. In radioligand binding studies, it was found that both anandamide and arachidonic acid inhibited the specific binding of [3H]PN 200-110 to transverse tubule membranes with IC(50) values of 4.4+/-0. 7 and 13.4+/-3.5 microM, respectively. These results indicate that anandamide, independent of cannabinoid receptor activation, directly inhibits the function of voltage-dependent calcium channels and modulates the specific binding of calcium channel ligands of the dihydropyridine class.

Effects of (+) and (-) enantiomers of calcium channel agonist, Bay K 8644, on mechanical and electrical responses of frog skeletal muscle.

The effects of (+) and (-) enantiomers of Bay K 8644, a Ca2+ channel agonist, on the mechanical and electrical properties of frog skeletal muscle fibers were investigated. In the concentration range of 10(-6) to 10(-5) M, both (+) and (-) enantiomers of Bay K 8644 significantly increased the maximum amplitudes of twitch responses. Both (+) and (-) enantiomers of Bay K 8644, at higher concentrations such as 10(-4) M, greatly depressed the amplitudes of twitches. Potentiating and depressing effects of (-) enantiomer of Bay K 8644 on twitch responses were significantly greater than those of the (+) enantiomer. At all concentrations used, both (+) and (-) enantiomers of Bay K 8644 significantly decreased the area under the tetanic force x time curve. In intracellular recordings, it was found that the depressing effects of both (+) and (-)-Bay K 8644 on tetanic contractions and twitch responses were due to the inhibition of action potentials. The inhibitory effect of (-) enantiomer of Bay K 8644 on action potentials also was significantly greater than that of the (+) enantiomer. In conclusion, present results suggest that, in contrast with cardiac muscle fibers, (+) and (-) enantiomers of Bay K 8644 have similar inhibitory effects on the electrical and mechanical properties of frog skeletal muscle fibers.