Hypoxanthine and thymidine are commonly used supplements in cell culture media, particularly for non-dividing cells or cells that have low rates of proliferation.
Hypoxanthine is a purine analog that is used as a precursor for nucleotide synthesis. It is converted to inosine monophosphate (IMP), which can then be converted to adenosine monophosphate (AMP) or guanosine monophosphate (GMP) through various enzymatic reactions. In cell culture, hypoxanthine is often used in combination with aminopterin, a folic acid antagonist, to inhibit de novo purine synthesis and select for cells that can use hypoxanthine as a salvage pathway for nucleotide synthesis.
Thymidine is a nucleoside that is used as a building block for DNA synthesis. It is incorporated into the growing DNA chain during replication, and cells with high rates of proliferation require high levels of thymidine to support DNA synthesis. In cell culture, thymidine is often used to supplement media for cells with low proliferation rates or cells that have been arrested in the cell cycle.
Hypoxanthine and thymidine are often used together as supplements in media for cells that have low rates of proliferation, such as Chinese hamster ovary (CHO) cells. The combination of hypoxanthine and thymidine can improve cell growth and viability, and can also improve the efficiency of transfection for stable cell lines. The optimal concentrations of hypoxanthine and thymidine can vary depending on the cell line and culture conditions, but concentrations ranging from 10-100 µM for each supplement are commonly used.