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 2:0006C, 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
bicarbonate -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 12 August 1994; accepted in final form 2 November 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.