TY - JOUR

T1 - Tissue kinetics, ion transport, and recruitment of mitochondria-rich cells in the skin of the toad (Bufo bufo) in response to exposure to distilled water

AU - Budtz, Poul Egede

AU - Christoffersen, Betina C.

AU - Johansen, Jesper S.

AU - Spies, Ingrid B.M.

AU - Willumsen, Niels J.

N1 - Key words Epidermis - Mitochondria-rich cells - Tissue kinetics - Ion transport - Proton secretion - Toad, Bufo bufo (Anura)

PY - 1995

Y1 - 1995

N2 - Mitochondria-rich cells (MRC) of the amphibian epidermis are responsible for active chloride uptake at low external salinity, and new MRCs are recruited in response to exposure to distilled (deionized) water. The time-course of this recruitment, the tissue kinetics and ion transport have been studied in toads (Bufo bufo) immediately before, and after 2,7, and 14 days exposure to distilled water. General epidermal structure was not affected. However, the numbers of MRCs per mm2 (DMRC) increased throughout the experiment as revealed by staining of epidermal sheets with AgNO3 (Ag) or methylene blue (MB). Part of the increased DMRC was accounted for by an increase in MRC subpopulation(s) that stained neither with Ag nor MB. The cell birth rate (Kb) decreased and cell loss by moulting (Kd) increased without any significant change in epidermal cell pool size, indicating a reduced apoptotic rate. The increase in DMRC was accompanied by a 3-fold increase in Cl- current (ICl). At day-2 there was a transient reduction in the ICl per MRC. H+ secretion was progressively reduced during prolonged exposure to distilled water. Thus, at day-2 MRCs appeared incompletely differentiated as indicated by decreased ICl and H+ flux per MRC, and by the increased proportion of MRCs unstained by Ag or MB. Full Cl- (but not H+) transport capacity, was restored at day-7. We conclude that increased DMRC following exposure to low external Cl-, rather than being due to an increased Kb, is the combined effect of a decreased apoptotic rate and an increased rate of differentiation, where morphological differentiation precedes functional differentiation.

AB - Mitochondria-rich cells (MRC) of the amphibian epidermis are responsible for active chloride uptake at low external salinity, and new MRCs are recruited in response to exposure to distilled (deionized) water. The time-course of this recruitment, the tissue kinetics and ion transport have been studied in toads (Bufo bufo) immediately before, and after 2,7, and 14 days exposure to distilled water. General epidermal structure was not affected. However, the numbers of MRCs per mm2 (DMRC) increased throughout the experiment as revealed by staining of epidermal sheets with AgNO3 (Ag) or methylene blue (MB). Part of the increased DMRC was accounted for by an increase in MRC subpopulation(s) that stained neither with Ag nor MB. The cell birth rate (Kb) decreased and cell loss by moulting (Kd) increased without any significant change in epidermal cell pool size, indicating a reduced apoptotic rate. The increase in DMRC was accompanied by a 3-fold increase in Cl- current (ICl). At day-2 there was a transient reduction in the ICl per MRC. H+ secretion was progressively reduced during prolonged exposure to distilled water. Thus, at day-2 MRCs appeared incompletely differentiated as indicated by decreased ICl and H+ flux per MRC, and by the increased proportion of MRCs unstained by Ag or MB. Full Cl- (but not H+) transport capacity, was restored at day-7. We conclude that increased DMRC following exposure to low external Cl-, rather than being due to an increased Kb, is the combined effect of a decreased apoptotic rate and an increased rate of differentiation, where morphological differentiation precedes functional differentiation.

U2 - 10.1007/BF00304512

DO - 10.1007/BF00304512

M3 - Journal article

VL - 280

SP - 65

EP - 75

JO - Cell and Tissue Research

JF - Cell and Tissue Research

SN - 0302-766X

IS - 1

ER -