Studies on the uptake and fate of hemoglobin pinocytosed by rat embryo fibroblasts cultured in normal or low magnesium media

Rat embryo fibroblasts were used to study the metabolism of FlHb in normal and low Mg²⁺ media. The fibroblasts were cultured in a modified Eagle's basal medium with a 10% calf serum supplement. The test substrate was in a concentration of 200 μg/ml. Accumulation and spike experiments were conducted to measure uptake and digestion. Turnover experiments measured rates of digestion of a pinocytosed substrate.

The accumulation was between 7 and 15 x 10⁻⁸ mmoles/mg cell protein. The half life for ingested FlHb was about 24 hours. There was considerable variation in accumulation per weight of cell protein when compared to the quantity of protein present. The lower the protein, the higher the accumulation. From dose dependent experiments there appeared to be surface binding saturation. The turnover rate was approximately 5% of the FlHb per day. There was no difference between the metabolism of FlHb by fibroblasts in the low Mg²⁺ or normal media.