Carbon dioxide balance in rat stomach and peripheral tissue: effects of histamine

Total carbon dioxide content of arterial, gastric venous, and peripheral venous blood of the rat has been measured by a gas extraction-gas solid chromatographic technique. In control animals total contents were 24 to 29 mmol/l and the venous/arterial ratio 1.148 +/- 0.020 (xav +/- SEM). Net change of carbon dioxide content (delta CO2) was 1.17 +/- 0.56 and 1.11 +/- 0.45 mmol/l in gastric and peripheral circulations and these were not significantly different from each other or zero. Infusion of histamine at 10 mg/kg/h led to oscillations in delta CO2 with peaks as high as 4.7 mmol/l and a period of 20 min. Similar oscillations occurred in the venous/arterial ratio with values up to 1.35. The results confirm previous reports of oscillations of carbon dioxide venous/arterial ratios induced by histamine as revealed by pulse radiolabeling experiments. The positive, if oscillatory, carbon dioxide balance in the presence of histamine supports the concept of sequestration of carbon dioxide in tissue with subsequent release on histamine stimulation.