T. Mauro et al., Acute barrier perturbation abolishes the ca(2+) and k(+) gradients in murine epidermis: Quantitative measurement using PIXE, J INVES DER, 111(6), 1998, pp. 1198-1201
Epidermal permeability barrier homeostasis requires the delivery of lipids
and hydrolytic enzymes by lamellar body exocytosis from the uppermost granu
lar cells, a process that is upregulated following barrier disruption. As l
amellar body secretion is controlled by ionic concentrations, especially Ca
2+ and K+, we used a quantitative technique, microbeam proton-induced X-ray
emission, to measure Ca2+, K+, Cl-, and P concentrations before and after
acute barrier perturbation by acetone applications, We found a steep gradie
nt of Ca2+ in normal tissue, peaking in the outer stratum granulosum, which
disappeared after barrier disruption, and partially reformed as the barrie
r recovered. A similar gradient, peaking somewhat lower in the epidermis (i
.e., at the stratum granulosum-stratum corneum interface), was found for K. Epidermal concentrations of K+ also decreased after barrier abrogation, a
lthough to a lesser extent than Ca2+. In contrast, P and Cl- demonstrated d
istribution gradients at baseline, which remained unchanged after barrier d
isruption. These studies quantitate the levels of Ca2+, K+, Cl-, and P with
in specific epidermal cell layers at baseline, and in relation to changes i
n permeability barrier integrity. Ca2+ and K+, but not Cl- or P, decrease a
fter barrier disruption, consistent with these two ion's role in barrier re
pair.