Abstract
It has already been reported that 45Ca uptake and total Ca content of guinea pig taenia coli increased when 40 mM K was added hypertonically to the external medium (1, 2). However, the addition of high-K isotonically, that is, an appropriate concentration of external sodium replaced by potassium, to depolarize and/or contract smooth muscle preparations, is the method that is widely employed. We have reported (3) that in isotonic high-K medium, which contained less Na, smooth muscle of taenia coli showed a shape of contracture different to that shown in hypertonic 40 mM K medium, which contained normal concentration of Na. In the present paper, changes in 45Ca uptake and tissue Ca of guinea pig taenia coli in isotonic 152 mM K/Na deficient medium were studied and the results were compared with those in hypertonic 40 mM K medium.
