AJP - Cell Physiology, Vol 232, Issue 1 37-C44, Copyright © 1977 by American Physiological Society
Stratum corneum of frog skin: inferences for studies of Na entry and transport pool
S. I. Helman and R. S. Fisher
Pieces of isolated stratum corneum from frog skins were studied.
Preliminary data showed that approximately 56% of the total sodium of split
skins was associated with the stratum corneum. In more detailed studies,
the sodium space estimated with 22Na and the volume of tissue water were
identical, averaging 0.95 mul/cm2. Thus, the stratum corneum contained
approximately 0.11 mueq Na+/cm2. Similar determinations of the sucrose,
mannitol, and inulin spaces of the stratum corneum gave mean values of
0.84, 2.21, and 1.84 mul/cm2, respectively. Surprisingly, the mannitol and
inulin spaces were observed to be at least twice as large as the space
occupied by the tissue water, and this can be interpreted to mean that
mannitol and inulin bind in appreciable amounts and thus are unsuitable
markers of the sodium space. Whereas the kinetics of sodium uptake and
washout could be described simply, similar studies for sucrose, mannitol,
and inulin were more complex and consistent with appreciable binding of the
substances to the stratum corneum.
