Circadian rhythms of acid secretion and electric parameters in rat gastric mucosa in vitro.

In male Wistar rats standardized from birth in LD 12:12 conditions (with light from 0700 to 1900 hr), samples of mucosa from the body of the stomach were isolated in vitro and mounted in a Ussing-type chamber. Spontaneous secretion of the hydrogen ion (H+)during 45 min of incubation was measured. Some electric parameters [transmucosal potential difference (PD) and electrical resistance (R)] were detected in the gastric mucosa both during H+ secretion and during inhibition of acid secretion by cimetidine. The variables studied were analyzed with the single cosinor method, and all revealed a circadian rhythm with acrophases during the dark span. The higher values of PD and R found during the dark hours are unrelated to acid secretion and may indicate a greater efficiency of ionic pumps and a limited passive permeability.