AJP - Cell Physiology, Vol 254, Issue 2 C310-C317, Copyright © 1988 by American Physiological Society
Relationship between quin2-determined cytosolic [Ca2+] and sweat secretion
K. Sato and F. Sato
Marshall Dermatology Research Laboratories, Department of Dermatology, University of Iowa School of Medicine, Iowa City 52242.
Although both methacholine (MCh)- and A23187-induced sweat secretion are
known to be strictly dependent on extracellular Ca2+, the role of
intracellular calcium concentration ([Ca2+]i) in eccrine sweating has not
been clarified. Partially purified eccrine secretory cells were prepared
from 400 to 600 isolated secretory coils of monkey sweat glands by serial
collagenase digestion and Percoll gradient centrifugation. The quin2 method
was used for semiquantitative determination of [Ca2+]i, MCh increased
[Ca2+]i in a dose-dependent, reversible, and pharmacologically specific
manner (from the resting [Ca2+]i of 80-320 nM) but failed to increase
[Ca2+]i in a Ca2+-free medium. A23187 (10(-7) M) increased [Ca2+]i to
approximately 900 nM. Theophylline (TH), isoproterenol (ISO), and forskolin
(FK) had no effect on the resting [Ca2+]i but, in combination, attenuated
the effect of subsequently added MCh and A23187. A23187 at 10(-7) M failed
to stimulate sweat secretion or CO2 production in vitro from the
quin2-loaded intact isolated sweat glands and dispersed sweat secretory
cells, respectively. The observed dissociation between the increase in
[Ca2+] may suggest either that MCh stimulation induces some unknown
excitatory signal in addition to a rise in [Ca2+] or that A23187-induced
Ca2+ influx into the secretory cells is much lower in undissociated sweat
glands.
