We investigated the inhibitory activity of nerve growth factor (NGF) on apoptosis of rat peritoneal mast cells (PMCs) and compared it with that of recombinant stem cell factor (rSCF), which is a mast cell growth factor. When PMCs were incubated up to 72 hours in the presence of control medium, internucleosomal fragmentation of DNA indicating apoptosis was detected by agarose gel electrophoresis and flow cytometry. The aged PMCs showed morphological changes typical for apoptosis, such as chromatin condensation and loss of microvilli of the cell membrane. Addition of NGF or rSCF prevented development of the characteristic DNA fragmentation and decreased the proportion of apoptotic cells with low DNA content values in a dose-dependent manner. Polyclonal antibody to NGF completely abolished the inhibitory activity of NGF but not of rSCF. NGF-induced PMCs were in the G0/G1 phase of the cell cycle, but rSCF transited them from the G0/G1 phase to the S/G2M phase, suggesting that NGF, unlike rSCF, may have no proliferation activity to PMCs. By flow cytometric analysis with antibodies to NGF receptors p75LNGFR and p140trk, we defined that PMCs expressed p140trk but not p75LNGFR. Addition of herbimycin A or K-252a, tyrosine kinase inhibitors, to NGF resulted in blockage of the NGF-induced p140trk phosphorylation and restriction of the inhibitory activity of NGF on apoptosis of PMCs. These results indicated that NGF suppressed apoptosis of rat PMCs through the p140trk tyrosine phosphorylation and possessed no proliferative activity. Thus, NGF may act as a key factor to promote survival of connective tissue-type mast cells.