A 1981 study expanded this research by treating various tissue and biological fluid preparations with 14C-labeled CSL, incubated at 37 °C (98.6 °F), and examined for lactylate hydrolysis. Assays used thin layer chromatography (TLC) with radioactivity detection to determine the levels of intact CSL and lactate (lactic acid). 14C-labeled CSL was found to undergo rapid hydrolysis in homogenized rat, mouse, and guinea-pig liver and intestinal mucosa, whereas CSL hydrolyzed much slower in rat and mice whole blood. In human duodenal mucosa, CSL rapidly hydrolyzed, while CSL showed no significant hydrolysis in human whole blood. Two metabolism studies were conducted by Hodge in 1961. The first showed that rats fed either SSL or CSL excreted only traces of lactate in fecal fat. The second study showed that 60% of the total 14C from 14C-labeled CSL was excreted as 14CO2 within 24 hours when fed to rats. The results were found to be virtually identical (58%) to a physical mixture of stearic acid and 14C-labeled lactic acid. A follow up study in mice and guinea-pigs was conducted in 1981 using 14C-labeled CSL and lactic acid. The authors concluded that excretion of both CSL and lactic acid followed a respiration pathway (excretion via CO2) followed by excretion as urine and feces. Most of the excretion occurred within the first 7 hours of the study. Chromatography on the urine showed most of the radioactivity co-eluted with lactic acid, implying that CSL was hydrolyzed during metabolism. A 1952 study by Schuler and Thornton established the oral LD50 of SSL in rats as over 25 g/kg body weight. Several feeding studies were conducted on rats starting in the 1950s. The researchers varied the test duration (27 days to 6 months), type of lactylate (CSL, SSL and SLA ), and dose levels (0.5 to 25%) as well as number of rats and gender. A few of the studies compared lactylates to physical mixtures of lactate salts (sodium or calcium), stearic acid, and lactic acid. In most studies, the lactylate-fed rats were compared to control groups fed normal diets. The primary conclusions established the no-observed-adverse-effect level (NOAEL) for rats at 2%.