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Growth stimulation by bombesin does not involve activation of Na+/H+ exchange in chick embryo otic vesicles in vitro
J I Gillespie1, F Giraldez, J R Greenwell
1Department of Physiological Sciences, Medical School, The University, Newcastle upon Tyne, England.
Abstract:
The effect of the mitogen bombesin on pHi in cells of the chick otic vesicle was studied using dual wavelength micro-spectrofluorimetric techniques. The results show that the bombesin did not produce an immediate alkalinization in quiescent otic vesicle cells nor a long-term change in pHi in vesicles reactivated to grow in culture. The recovery of pHi from an acid load, caused by an NH4 pulse, involved both Na+/H+ exchange and Na+:HCO3 influx mechanisms, neither of which was influenced by bombesin. These observations do not fit with a general model whereby pHi is a universal signal for DNA replication and cell proliferation.