AJP - Regulatory, Integrative and Comparative Physiology, Vol 249, Issue 2 172-R178, Copyright © 1985 by American Physiological Society
Calcium exchange in isolated cutaneous epithelium of toad Bufo marinus
B. R. Grubb and P. J. Bentley
The Ca content of isolated cutaneous epithelium of toads (Bufo marinus) was
5 mmol/kg wet wt (compared with approximately 300 mmol/kg wet wt for intact
skin), of which approximately 1.7 mM is not readily exchangeable with
external 45Ca. After incubation in a solution containing 45Ca, loss of the
accumulated isotope in an isotope-free medium is almost complete in 2 h.
This efflux or washout is reduced by the presence of external Ca- and
Na-free media and by La. Loss of Ca from the epithelium may thus reflect
the presence of several mechanisms including a Ca-Ca exchange and a Ca-Na
exchange. The effect of La (2 mM) was greater than that of a Na- and
Ca-free medium, possibly reflecting the presence of an uncoupled Ca
extrusion or extrusion by a Ca-ATPase (pump) mechanism. Drugs (ouabain and
amiloride) that, respectively, increase or decrease levels of internal Na
had no significant effects on efflux or accumulation of Ca. Vasopressin was
also without such effects on Ca.
