Acid secretion by JME epithelial cultures. (A) Rates of acid secretion in the absence (filled symbols) and presence (open symbols) of 10 µM ZnCl₂. Serosal pH 7.4 and mucosal pH was adjusted to 7, 7.4, and 8; n = 5. *, significantly different from control; t test. (B) Zn-sensitive rates of acid secretion (calculated as the difference from data in A) resulted in an average slope of 339 ± 33.6 nmol × h⁻¹ × cm⁻² × pH⁻¹ and a threshold pH of 6.90 (by linear regression).