Regulation of intracellular pH in sheep cardiac Purkinje fibre: interactions among Na+, H+, and Ca2+1

Experiments were performed on sheep cardiac Purkinje fibres using pH- and sodium-selective microelectrodes, while simultaneously measuring tension, to determine if the fall in intracellular pH (pHi) following a rise in intracellular Na+ activity (aiNa) is caused by inhibition or reversal of acid extrusion on Na+-H+ exchange. A rise in aiNa was induced either by using the cardioactive steroid strophanthidin to inhibit the sarcolemmal Na+-K+ pump or by increasing the frequency of stimulation (0-4 Hz). Both of these manoeuvres led to an increase in aiNa and a decrease in pHi. Following exposure to strophanthidin, amiloride (an inhibitor of sarcolemmal Na+-H+ exchange) produced a decrease in both pHi and aiNa. These effects of amiloride increased with decreasing pHi, indicating that acid extrusion on Na+-H+ exchange is stimulated by the fall in pHi. The changes in intracellular Na+ and H+ caused by amiloride were quantitatively consistent with an electroneutral stoichiometry. The fall in pHi during strophanthidin exposure is therefore not caused by inhibition or reversal of acid extrusion Na+-H+ exchange. It is likely that the fall in pHi during a rate increase is also independent of Na+-H+ exchange. This is because (i) it has been shown previously to occur in the presence of amiloride and (ii) the calcium antagonist D600 completely abolished the stimulation-dependent fall in pHi. It is concluded that the intracellular acidosis following inhibition of the sarcolemmal Na+-K+ pump or following an increase in the rate of stimulation is secondary to a rise in intracellular calcium.     

The Day-Hospital of the University Hospital,Bobo Dioulasso: An Example of Optimized HIV Management in Southern Burkina Faso

ObjectivesTo evaluate the epidemiological evolution of patients with HIV (PtHIV), between 2002 and 2012, in a day-hospital that became an HIV reference centre for south-west Burkina Faso.ResultsA total of 7320 patients have been treated at the centre since 2002; the active file of patients increased from 147 in 2002 to 3684 patients in 2012. Mean age was stable at 38.4 years and the majority were female (71%). The delay to initiation of antiretroviral (ARV) treatment after HIV diagnosis decreased from 12.9 months in 2002 to 7.2 months in 2012. The percentage of PtHIV lost to follow-up, untreated for HIV and deaths all decreased after 2005. Voluntary anonymous screening and/or an evocative clinical picture were the main reasons for HIV diagnosis, usually at a late stage (41.1% at WHO stage 3). Virological success increased due to a decrease in time to initiation of ARV treatment and an increase in percentage of patients treated (90.5% in 2012, mainly with 1^st line drugs). However, there was also a slight increase in the rate of therapeutic failures and the percentage of patients who progressed to 2^nd or 3^rd line-ARVs.ConclusionOur day-hospital is a good example of the implementation of a specialist centre for the management of PtHIV in a resource-limited country (Burkina Faso).