Temporal variations in protein tyrosine kinase activity in leukaemic cells: response to all-trans retinoic acid.

Protein tyrosine kinases (PTKs) play a critical role in the modulation of a wide variety of cellular events such as cell division, differentiation and metabolism. Regulation of PTK activity must be tightly controlled as over-stimulation is known to impair normal cell growth, resulting in oncogenic transformation. Since evidence suggests that dynamic oscillatory behaviour occurs in metabolic control processes, we investigated the patterns of oscillatory behaviour in the total protein content and enzyme activity of PTK exhibited by proliferating and differentiating human acute promyelocytic cells. Distinct rhythmic patterns of oscillatory behaviour were observed in both the amount of extractable protein and PTK enzyme activity. Rhythmic characteristics such as period and amplitude were significantly modulated following treatment with all-trans retinoic acid, an inducing agent. These results support the view that dynamic oscillatory control processes may play an important role in regulating cellular behaviour.