Study on the growth promoting capacity of calf and fetal bovine serum for animal cells «in vitro». II: Electrophoretic study and survey on the antiproteolytic activity of pools of calf and fetal bovine serum

Calf serum and fetal bovine serum present great variability as to its growth promoting efficiency (GPE). As supplement of culture media to cultivate cells of animal origin they stimulate the "in vitro" multiplication and maintain cell viability. When fourteen lots of calf sera of variable GPE had the total protein contents as well as the percentages of serum fractions determined, no significant differences that could possibly explain the variability of the GPE were observed. Evaluation of the antiproteolytic activity of nineteen lots of calf serum and eighteen serum lots of younger calves showed that the former exhibited lower antiproteolytic titers (1:40 to 1:80) than the latter (1:80 to 1:160). Twelve lots of fetal bovine serum studied in parallel, showed the highest concentration of antiproteolytic factors, with titers equal to 1:320. Sera of bovine origin, but not fetal sera, are usually heat-inactivated, what was demonstrated to be responsible for the decrease of the antiproteolytic activity of 75% of the lots tested. This could explain the inability of certain heat-inactivated sera in promoting multiplication of some cells "in vitro", as verified with primary monkey kidney cells. The results obtained in this study indicated the convenience of submiting each lot of serum to be introduced in cell culture to previous determination of its characteristics, such as growth promoting efficiency, antiproteolytic activity and also toxicity, absence of extraneous agents, etc., in order to minimize the possibility of using serum lots of questionable quality, thus preventing not only the loss of cell lines, but also undesirable and sometimes expensive delays. O soro de vitelas e o soro fetal bovino apresentam grande variabilidade no que se refere à sua capacidade promotora de crescimento (CPC) e são empregados no cultivo de células de origem animal, suplementando os meios de cultura, com a finalidade de estimular a multiplicação das células "in vitro", assim como manter a viabilidade das mesmas. Quando 14 lotes de soro de vitelas apresentando diferentes CPC tiveram seu teor total de proteínas, assim como as percentagens séricas presentes determinados, não foram observadas diferenças significativas que justificassem a variação daquela capacidade. Na avaliação da atividade antiproteolítica (AA) de 19 lotes de soros de vitelas e de 18 de soros de bezerros de tenra idade, foi constatado que os primeiros apresentavam títulos antiproteolíticos mais baixos (1:40 a 1:80)