Calcium efflux from amphibian sciatic nerve

Eight Xenopus laevis were injected intraperitoneally with 45CaCl2 and 16-18 h later an unbranched section from each sciatic nerve was removed. Efflux measurements of nerve from which the perineurial sheath had been removed could be described by three compartments of approximately equal size with half-lifes of 2.37 +/- 0.76 (SD), 30.3 +/- 17.3 and 196 +/- 61 min, the shortest lived compartment representing diffusion from the extracellular space with a coefficient of diffusion of 2.1 +/- 0.7 X 10(-6) cm2/s. Efflux from nerve in which the perineurium remained intact was characterized by a half-life of 862 +/- 399 min resulting from the sheath acting as a diffusion barrier of permeability 3.4 +/- 1.6 X 10(-7) cm/s. The perineurium was found to bind or sequester a quantity of calcium 1-2 times that contained in an equal volume of plasma.