Evidence for a Na+/Ca2+ exchange mechanism in frog skin epithelium
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Evidence for a Na+/Ca2+ exchange mechanism in frog skin epithelium. / Madsen, K H; Brodin, Birger; Nielsen, R.
In: Pflügers Archiv - European Journal of Physiology, Vol. 437, No. 2, 1999, p. 175-81.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Evidence for a Na+/Ca2+ exchange mechanism in frog skin epithelium
AU - Madsen, K H
AU - Brodin, Birger
AU - Nielsen, R
PY - 1999
Y1 - 1999
N2 - In the present study we investigated the possible existence of a Na+/Ca2+ exchange mechanism in the basolateral membrane of the frog skin epithelium and whether such a mechanism plays a role in the regulation of transepithelial Na+ transport. Cytosolic calcium ([Ca2+]i) was measured with the probe fura-2 in a set-up in which pieces of tissue were mounted on the stage of an epifluorescence microscope. Na+ transport was measured as the amiloride-sensitive short-circuit current (Isc) using a conventional voltage clamp. Basal [Ca2+]i was 65+/-6 nM (n=15). Removal of Na+ from the mucosal solution had no effect on [Ca2+]i. When Na+ was removed from the serosal solution, [Ca2+]i increased biphasically to a peak of 220+/-38 nM (n=8, P=0.006). Readdition of Na+ to the serosal solution returned [Ca2+]i to control level. The serosal Na+ gradient and changes in [Ca2+]i were closely correlated; stepwise changes in serosal Na+ were followed by stepwise changes in [Ca2+]i. These observations indicate the existence of a Na+/Ca2+ exchange mechanism in the basolateral membrane of the frog skin epithelium. The transepithelial Na+ transport decreased from 13.2+/-1.8 to 9.2+/-1.5 microA cm-2 (n=8, P=0.049) when Na+ was omitted from the serosal solution. When this protocol was repeated in the absence of serosal Ca2+, Na+ transport decreased similarly from 16.7+/-1.7 to 11.6 +/-1. 8 microA cm-2 (n=6, P=0.004). We conclude that it is unlikely that the observed decrease in Isc after removal of serosal Na+ is due to an increase in [Ca2+]i per se.
AB - In the present study we investigated the possible existence of a Na+/Ca2+ exchange mechanism in the basolateral membrane of the frog skin epithelium and whether such a mechanism plays a role in the regulation of transepithelial Na+ transport. Cytosolic calcium ([Ca2+]i) was measured with the probe fura-2 in a set-up in which pieces of tissue were mounted on the stage of an epifluorescence microscope. Na+ transport was measured as the amiloride-sensitive short-circuit current (Isc) using a conventional voltage clamp. Basal [Ca2+]i was 65+/-6 nM (n=15). Removal of Na+ from the mucosal solution had no effect on [Ca2+]i. When Na+ was removed from the serosal solution, [Ca2+]i increased biphasically to a peak of 220+/-38 nM (n=8, P=0.006). Readdition of Na+ to the serosal solution returned [Ca2+]i to control level. The serosal Na+ gradient and changes in [Ca2+]i were closely correlated; stepwise changes in serosal Na+ were followed by stepwise changes in [Ca2+]i. These observations indicate the existence of a Na+/Ca2+ exchange mechanism in the basolateral membrane of the frog skin epithelium. The transepithelial Na+ transport decreased from 13.2+/-1.8 to 9.2+/-1.5 microA cm-2 (n=8, P=0.049) when Na+ was omitted from the serosal solution. When this protocol was repeated in the absence of serosal Ca2+, Na+ transport decreased similarly from 16.7+/-1.7 to 11.6 +/-1. 8 microA cm-2 (n=6, P=0.004). We conclude that it is unlikely that the observed decrease in Isc after removal of serosal Na+ is due to an increase in [Ca2+]i per se.
KW - Algorithms
KW - Animals
KW - Biological Transport
KW - Calcium
KW - Cytosol
KW - Enzyme Inhibitors
KW - Epithelium
KW - Extracellular Space
KW - Female
KW - Rana temporaria
KW - Skin
KW - Sodium
KW - Thapsigargin
M3 - Journal article
C2 - 9929556
VL - 437
SP - 175
EP - 181
JO - Pflügers Archiv - European Journal of Physiology
JF - Pflügers Archiv - European Journal of Physiology
SN - 0031-6768
IS - 2
ER -
ID: 37899848