Active Transport of Calcium by Intestine: Studies with a Calcium Activity Electrode
Previous studies have demonstrated an intestinal mechanism which transfers calcium from the mucosa to the serosa in vitro (Rasmussen, 1959; Harrison & Harrison, 1960; Schachter, Dowdle & Schenker, 1960a,b; Finkelstein & Schachter, 1962; Schachter, Kowarski, Finkelstein & Ma, 1966; Schachter, Kowarski & Reid, 1967) or to the bloodstream in vivo (Wasserman, Kallfelz & Comar, 1961; Krawitt & Schedl, 1968) against concentration and electrical potential gradients. The transport is dependent on oxidative phosphorylation (Schachter & Rosen, 1959), and is rate-limited (Schachter et al, 1960a); it is relatively specific for Ca as compared with other cations (Schachter & Rosen, 1959; Schachter et al., 1960a) and is competitively inhibited by certain cations and actively transported hexoses (Schachter et al., 1960b; Schachter, Kimberg & Schenker, 1961). Moreover, it is dependent on vitamin D (Harrison and Harrison, 1960; Schachter et al., 1961, 1967) and varies in the rat with growth, pregnancy, and the level of dietary Ca (Schachter et al., 1960a; Kimberg, Schachter & Schenker, 1961). These properties suggest that the mechanism might be classified as an active transport. In earlier studies (Schachter et al., 1960a) a murexide technique was used to demonstrate that most of the Ca transferred to the serosal surfaces of everted gut sacs in vitro was ionized, and it was concluded that the mechanism is probably a cation pump.
KeywordsSerosal Surface Activity Gradient Cation Pump Serosal Medium Active Cation Pump
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