Uptake of orthophosphate by rabbit vagus nerve fibres.

Abstract

SUMMARY1. The uptake of orthophosphate and its incorporation into ATP, ADP, and creatine phosphate (CrP) were studied in desheathed rabbit vagus nerve.2. Using 32p labelled orthophosphate, the total amount of labelled phosphate taken up by the preparation was continuously recorded in a perfusion apparatus. For measuring the incorporation into phosphorylated compounds, phosphate esters and inorganic phosphate were extracted, separated and their total amount and radioactivity determined.3. The total uptake of phosphate was found to be a biexponential function of time.4. The time constant of the first process was 10-20 min and independent of the extracellular phosphate concentration, the final amount labelled by this process was relatively small and proportional to external phosphate, increasing from 0-026 m-mole/kg wet nerve at 0-04 mm phosphate to 114 m-mole/kg at 5 mm.5. The time constant of the second process depended on the extracellular phosphate concentration varying from 4624 min at 0*04 mm to 210 min at 5 mm. The final amount labelled by this process was 5-6 m-mole/kg wet wt. and independent of the extracellular phosphate.6. The kinetics of the slow uptake were consistent with the presence of a saturable process and a non-saturable one.7. Extraction of ATP, ADP, and the sum of CrP and Pi, showed that the total amount of these compounds remained constant for 2 hr while their radioactivity increased slowly, approximately at same rate as the slow fraction.8. Increasing the external phosphate from 0 04 to 5 mm increased the amount of labelled ATP.

Glycine fluxes in squid giant axons.

“…The pair axon method was used as in a previous study (Caldwell & Lowe, 1970). The results, given in Table 5, show that the orthophosphate uptake is greatly reduced when Na+ is replaced by choline or Li+, and that in this orthophosphate uptake in squid axons is similar to that in rabbit vagus nerve (Anner, Ferrero, Jirounek & Straub, 1975). It can be concluded therefore that the method used to replace Na by choline is satisfactory, and that in fact under normal conditions in artificial sea water there is no Na-sensitive glycine influx.…”

Efflux of inorganic phosphate from mammalian non‐myelinated nerve fibres.

“…Previous experiments have shown that the influx of orthophosphate into mammalian non-myelinated nerve fibres is slow, much slower than its rate of metabolic turnover (Anner, Ferrero, Jirounek & Straub, 1975). Further it was found that the influx can be divided into a linear and a saturable term and that the saturable influx is dependent on the presence of sodium ions (Anner, Ferrero, Jirounek, Jones, Salamin & Straub, 1976).…”

“…The techniques used were similar to those of previous experiments (Anner et al 1975(Anner et al , 1976. In brief, for measuring the influx, or for loading the tissue with radiophosphate, a desheathed cervical vagus nerve of a rabbit was mounted in a narrow polyethylene tube that was perfused with Locke or modified Locke.…”

“…The supernatant was carefully removed, and both supernatant and chloroform fraction were counted. In some experiments the different water soluble compounds of the supernatant were separated by column chromatography, as described elsewhere (Anner et al 1975).…”

Stanniocalcin: A molecular guard of neurons during cerebral ischemia

“…Phosphate ( 32 Pi) uptake was measured as described (19) at 37°C in Locke's buffer (20) Cell Viability Assay and Luciferase Assay for ATP Monitoring. Cell viability was assessed by trypan blue exclusion (BDH).…”