Adaptive differentiation of avian exocrine cells alters their phi-response
to machr-activation.
Bentz, Christine, and Jan-Peter Hildebrandt.
Physiologisches Institut, Medizinische Fakult[umlaut]at,
Universit[umlaut]at des Saarlandes, D - 66421 Homburg/Saar, FRG
APStracts 2:0022C, 1995.
Muscarinic receptor-mediated changes in intracellular proton concentration
(pHi) were measured in isolated BCECF-loaded cells from the exocrine nasal
gland of freshwater-fed ducklings (Anas platyrhynchos) suspended in icarbonate
-containing media. The pHi-recovery from an acid-load was sensitive to
amiloride, required sodium ions in the external medium, and was independent
of added bicarbonate. These findings are consistent with the hypothesis that
the pHi-recovery was mediated by a Na+/H+-exchanger. Muscarinic activation of
cells resulted in a sustained cytosolic alkalinization that was sensitive to
atropine and was blocked by amiloride. Activation of protein kinase C (PKC)
or inhibition of protein phosphatases mimicked the effect of receptor
-activation on pHi, whilst inhibitors of PKC blocked the response indicating
that phosphorylation of a major pHi-control mechanism results in a shift of
pHi to more alkaline values. In contrast, fully differentiated salt gland
cells isolated from nasal glands of salt-stressed ducklings responded to
muscarinic receptor-activation with a transient cytosolic acidification.
These findings raise the question whether the cytosolic alkalinization in
mAChR-activated naive cells may serve as a signal or a permissive factor for
the initiation of adaptive growth and/or differentiation processes observed
in the salt glands of salt-stressed birds.
Received 15 August 1993; accepted in final form 4 October 1994
APS Manuscript Number C547-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1994 The American Physiological Society.
Published in APStracts on 27 February 1995.