AJP - Gastrointestinal and Liver Physiology, Vol 245, Issue 1 133-G142, Copyright © 1983 by American Physiological Society
Basal-lateral and intracellular membrane populations of rat exorbital lacrimal gland
A. K. Mircheff, C. N. Conteas, C. C. Lu, N. A. Santiago, G. M. Gray and L. G. Lipson
With the goal of isolating and identifying plasma membrane vesicle
populations from epithelial cells of the rat exorbital lacrimal gland, we
have designed an analytical fractionation of homogenates of the gland
parenchyma. This fractionation utilizes separation procedures based on
three independent physical properties of subcellular particles:
sedimentation coefficient, density, and density after interaction of
membrane cholesterol with digitonin. A commonly accepted marker for
basal-lateral membranes, Na-K-ATPase, is associated with at least two
physically distinct membrane populations. One population can be identified
as basal-lateral membrane fragments on the basis of its fractional and
specific contents of Na-K-ATPase; it accounts for 50% of the total
Na-K-ATPase activity, enriched 29-fold with respect to the initial
homogenate. With these values we calculate that the sample of basal
membranes has been purified 60-fold with respect to the initial homogenate.
The remaining Na-K-ATPase activity appears to be associated, at three- to
fivefold lower specific activities, with intracellular membrane
populations. We speculate that these populations have been derived from the
Golgi complex.
