Cell cycle analysis in the cardiac and neuroepithelial tissues of day 10 rat embryos and the effects of phosphoramide mustard, the major teratogenic metabolite of cyclophosphamide

Abstract

Using the autoradiographic technique of percent labeled mitoses (PLM), total cell cycle length (Tc) and lenght of the cell cycle phases G₁, S, G₂, and M have been estimated for the neuroepithelium and heart of day 10 rat embryos. The Tc for the neuroepithelium was estimated to be 9.45 hr, consisting of G₁ of 1.24 hr, S of 6.15 hr, G₂ of 1.34 hr, and M of 0.72 hr. The Tc for the heart was estimated to be 13.37 hr, consisting of G₁ of 4.30 hr, S of 7.01 hr, G₂ of 1.81 hr, and M of 0.25 hr. Comparison of cell cycle parameters in these two tissues indicates that the longer cell cycle in heart tissue is related primarily to an increase in G₁. If embryos are exposed to the major teratogenic metabolite of cyclophosphamide, phosphoramide mustard, cell cycle analysis reveals that the S phase of the neuroepithelial cell cycle is lengthened and cells are either slowed or arrested in G₂.