[abstract] N2 ELIMINATION IN HUMANS AFTER ACUTE INGESTION OF DIETARY FAT.

Abstract

BACKGROUND: Theory suggests (UHM, 20(suppl.): 96, 1994) that the rate of N2 elimination may be increased during postprandial lipemia due to an increase in N2 solubility in the blood. The purpose of this study was to determine if the rate of N2 elimination could be altered by manipulating blood lipid levels through a fatty meal. METHODS: Twenty N2 elimination experiments were conducted in ten volunteers, once each after a high fat meal (75 g fat/m2 body surface area) and after a low fat, control meal, in random order. Subjects rebreathed a normoxic Ar-O2 mixture on a closed-circuit system for 125 min and the cumulative amount of N2 eliminated was determined every 10 minutes using gas chromatography. Over the course of the experiment measurements of heart rate (HR), stroke volume (SV) (by impedance cardiography), cardiac output (CO), calf blood flow (CBF) (by strain-guage plythesmography), arterial blood pressures, hematocrit (Hct), and plasma triglycerides (TG) were made. RESULTS: TG increased by an average of 83.8percent after the fatty meal compared to the control meal. No significant difference in N2 elimination rate was observed during the postprandial lipemia compared to the control state. Significant increases (P less than 0.001) in HR (10.3percent), SV (6.5percent), and CO (20.3percent) were seen after the high fat meal, while small but significant (P less than 0.02) decreases in diastolic (2.9percent), systolic (1.7percent), and mean (1.1percent) arterial blood pressures were observed. Hct and CBF were not significantly changed. CONCLUSIONS: Elevating blood lipid content through a high fat meal did not measurably increase N2 elimination despite increases in CO and in the capacity of the blood to carry dissolved N2 . We hypothesize that the observed lack of an increase in the rate of elimination may be the result of an increase in blood flow primarily in the splanchnic area accompanied by a decrease in the perfusion of tissues which contain larger stores of N2. (Supported in part by NOAA award #R-DP5 to Research Foundation of the State University of New York for New York State Sea Grant Institute and the Jefferson Davis Memorial Fellowship)