Effect of Alkaline Media on the Growth of Embryonic Chick Tibiotarsi in Organ Culture

SINCE blood has a p H of about 7.4, media used for organ and tissue culture are usually adjusted to this hydrogen ion concentration. However, when the chemically defined medium BGJ b 1 was first formulated, sodium bicarbonate was added in excess (3.5 g/l.), with the result that the medium had a p H of 7.68 when equilibrated with 5 per cent carbon dioxide in air. Mouse fallopian tubes continued to function 2 and embryonic long bones developed 1 under these alkaline conditions. Paff 3 studied the effect of hydrogen ion concentration on embryonic chick femora cultivated on plasma clots in the presence of both air and 5 per cent carbon dioxide in air. The p H of the media under these conditions was 7.8–8.0 and 7.0–7.3 respectively. After cultivation for 14 days, the femora grown at the lower p H contained more bone and had a higher calcium content. However, the conditions required for mineralization may be quite different from those needed for cell division and cellular hypertrophy in the cartilaginous rudiment. We have, therefore, investigated the influence of hydrogen ion concentration on the growth of cartilaginous tibiotarsi of the embryonic chick. This was done by varying the bicarbonate concentration of the medium while maintaining a constant atmosphere of 5 per cent carbon dioxide in air.