Reflective densitometry of Western blots to quantitate the developmentally regulated accumulation of myosin light chain 3.

We have employed a monoclonal antibody to fast myosin alkali light chains to study the accumulation of myosin light chain 3 (MLC3f) in the breast and limb musculature of developing quail embryos using quantitative densitometry of Western blots. Our analyses reveal that MLC3f is first detected in the breast muscle of 11 day embryos and accumulates at a constant rate until hatching at day 16. This data suggests, by extrapolation, that MLC3f accumulation is initiated at day 10 in embryonic breast muscle. MLC3f is also first detected in the limb muscle of 11 day embryos, but does not accumulate rapidly until after day 13. These results demonstrate the effective use of reflective densitometry in the study of developmental problems and in the quantitation of Western blots in general.