The proposed work deals with the study of acid production in the intact, isolated amphibian gastric mucosa, and in particular with enzymes, carrier molecules or specific pores which may be located on the opposing surfaces of the mucosal cells. Special attention is directed towards the mode of C1 minus movemovement whether by exchange for C1 minus or for HCO3 minus ion, or by passive diffusion across apical or basal-lateral surfaces. To accomplish this, several different methods are to be used to estimate the physiological tissue C1 compartment, and to study the effects of modifying the respective bathing solutions on this C1 pool. Work is also to be directed towards estimation of changes in cell pH from the tissue levels of adenine nucleotides and creatine compounds, and the effects of these changes on acid secretory rate and C1 exchange. BIBLIOGRAPHIC REFERENCE: Relationship of nutrient surface ATPase to acid secretion in frog gastric mucosa, A.B. Kircher & R.P. Durbin. In "Gastric Hydrogen Ion Secretion," ed. by D.K. Kasbekar, G. Sachs & W.S. Rehm. Marcel Dekker, N.Y. (1976).