Rectal tissue transport kinetics by both everted and non-everted unfed tissues.

A) Mg2+, B) Ca2+, and C) H+ fluxes in the serosal fluid for non-everted (N = 4) and the mucosal fluid for everted (N = 5) rectal tissue of unfed C. auratus. Cortland saline containing 0–32 mM MgSO4 was applied to the mucosal surface. Positive values in non-everted preparations indicate appearance in the serosal fluid (suggesting mucosal-to-serosal movement) and negative values in everted preparations indicate disappearance from the mucosal fluid (suggesting mucosal-to-serosal movement). Data represent the mean flux ± S.E.M. Regression analysis revealed a significant (p 2+ concentration and Mg2+ transport rate fitting a Michaelis-Menten curve with single saturation. No significant relationship between Mg2+ concentration and Ca2+ or H+ transport rates was found. See text for more details.