Effect of medium osmolality on the growth of murine continuous marrow cultures.

The effect of medium osmolality was examined in primary, continuous bone-marrow cultures established from TO strain mice. The non-adherent cell population increased exponentially between weeks 2 and 5 and thereafter declined steadily. The number of CFU-GM followed a similar pattern but showed greater variability. The optimum osmolality in 4 week old cultures was found to be about 345 mosmol/kg which was higher than the plasma osmolality (n = 20; mean = 323.3 mosmol/kg; range = 313-331). Maximum non-adherent cell numbers were found at about 345 mosmol/kg (better than half-maximum between 320 and 370 mosmol/kg). CFU-GM numbers in the culture supernatant were maximal at about 355 mosmol/kg (better than half-maximum between 320 and 400 mosmol/kg). An adherent layer developed over a wider range of osmolality than supported granulopoiesis (better than half-maximum between 258 and 402 mosmol/kg). It was necessary to increase the osmolality of Fischer's medium in order to obtain maximum growth.