QUANTITATIVE HISTOLOGIC DISTRIBUTION OF ADENOSINE-3',5'-MONOPHOSPHATE IN THE RAT STOMACH IMPROVED PROCEDURE FOR THE LUMINESCENCE ASSAY

Abstract

Procedural improvements of the luminescence method for determination of adenosine-3',5'-monophosphate (cAMP) in submilligram samples, e.g., fresh-frozen microtome sections of tissue or l0-µl volumes of homogenate, were developed for technical simplification, time-saving and increased analytical precision and then applied to determination of the quantitative histologic distribution of cAMP in the body of the glandular stomach of the fed and fasted rat. In fasted rats, a sharp peak in cAMP concentration (0.12 pmole/µg protein-nitrogen, approximately ≈ 3.3 pmoles/mg wet weight) was observed in the parietal mucous neck cell zone and the values fell off rapidly to about one-half peak value in the chief cell region and remained in this range into the muscle layer. When fed, additional second and third peaks appeared in the chief cell and muscle zones, each about l0% less than the first peak. The histologic position and the height of the first peak did not change significantly from that in the fasted state. For comparison, homogenates of glandular stomach of fed rats were found to have cAMP values in the range, 1.9-2.4 pmoles/mg wet weight. The findings are discussed in relation to quantitative distribution and function of histamine and histidine decarboxylase and to acid secretion.