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The pharmacology of the large-conductance K(+) (BK) channel in human osteoblasts is not well defined, and its role in bone is speculative. Here we assess BK channel properties in MG63 cells and primary human osteoblasts and determine whether pharmacological modulation affects cell function. We used RT-PCR and patch-clamp methods to determine the expression of BK channel subunits and cell number assays in the absence and presence of BK channel modulators. RT-PCR showed the presence of KCNMA1, KCNMB1, KCNMB2, KCNMB3, and KCNMB4 subunits. The BK channel was voltage dependent, with a mean unitary conductance of 228.8 pS (n = 10) in cell-attached patches (140 mM K(+)/140 mM K(+)) and a conductance of 142.5 pS (n = 16) in excised outside-out and 155 pS (n = 6) in inside-out patches in 3 mM K(+)/140 mM K(+). The selectivity ratio (ratio of K(+) to Na(+) permeability) was 15:1. The channel was blocked by tetraethylammonium (TEA, 0.3 mM), iberiotoxin (5-60 nM), tetrandrine (5-30 microM), and paxilline (10 microM) and activated by isopimaric acid (20 microM). BK channel modulators affected MG63 cell numbers: TEA and tetrandrine significantly increased cell numbers at low concentrations (3 mM and 3 microM, respectively) and reduced cell numbers at higher concentrations (>10 mM and >10 microM, respectively). Neither iberiotoxin (20-300 nM) nor slotoxin (300 nM) affected cell numbers. The increase in cell numbers by TEA was blocked by isopimaric acid. TEA (0.1-3.0 mM) significantly increased mineralization in primary osteoblasts. In conclusion, the BK channel has a distinctive pharmacology and is thus a target for therapeutic strategies aimed at modulating osteoblast proliferation and function.

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Background Alternative administration methods are emerging as a key area of research to improve clinical efficacy of antibiotics and address concerns regarding multi-drug resistance. Extended intermittent infusions or continuous infusions of antibiotics exhibiting time-dependent kill characteristics may be favourable in critically ill septic patients, but more evidence is needed to determine best practice. Objective To find out whether any common practice exists for intravenous antibiotic administration in critical care units across UK NHS Trusts, and identify factors influencing the adoption of extended or continuous infusions. Setting UK hospitals. Method UK critical care pharmacists were invited to participate in a survey on behalf of all 240 critical care units via a UK Clinical Pharmacy Association message board. The survey focused on administration practices for 22 antibacterial agents. Main outcome measure Antibiotic administration method. Results Responses were received covering 64 units, a response rate of 26.2%. Common, but not uniform administration methods were apparent for 17/22 antibiotics. Four antibiotics (piperacillin/tazobactam, doripenem, meropenem and vancomycin) were more likely to be administered as continuous or extended-intermittent infusions. Choice of administration method was especially influenced by altered pk/pd properties in sepsis or severe burns patients, or by the presence of organisms requiring high minimal inhibitory concentrations. Conclusion Unlicensed alternative practices of antibiotic administration are widespread but only weak evidence exists of any patient benefit, such as reduced length of stay in critical care, and none showing improvement in mortality. Further research is needed to determine whether extended infusion methods offer clinically meaningful advantages over shorter licenced administration methods in patients in critical care units.