K depletion and nh4cl acidosis increase apical insertion of studded
membrane in type a-intercalated cells.
Narbaitz, Roberto, Selva Murugesan, and David Z. Levine.
Department of Anatomy and Neurobiology and Division of Nephrology,
University of Ottawa, Ottawa, Canada
APStracts 2:0204F, 1995.
To examine the effects of K-depletion and metabolic acidosis on the
prevalence and distribution of H+-ATPase-related studs at the luminal
plasma membrane of A-type intercalated cells (A-ICs), we conducted a
quantitative electron microscopical study on the cortical collecting
ducts (CCDs) of control, NH4Cl-loaded, and K-depleted rats. The
percentage of A-ICs was slightly increased in the K-depleted but not
in the acidotic rats. A-ICs were considered "active" when
they presented a semi-continuous row of 9-10 nm studs at the
cytoplasmic face of the apical membrane, and "inactive" when
all of the apical membrane was devoid of studs. The percentage of
active A-ICs was greatly increased in acidotic (87.2%) and K-depleted
(79.3%) rats, compared to controls (41.6%). These results give a
quantitative expression to the general view that acidosis elicits
insertion of studded membrane in the apical plasma membrane of A-ICs.
Further, we show for the first time, that an increase in the membrane
insertion of H+-ATPase is also part of the response to K-depletion.
Received 12 July 1995; accepted in final form 15 November 1995.
APS Manuscript Number F225-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95