Homobrassinolide is a plant hormone implicated in plant growth and development. Its effect on animal metabolism was less known to date. We have investigated its effect on the marker enzymes such as alkaline phosphatase and creatine kinase in selected rat tissues-brain, heart, liver, kidney, skeletal muscle and testis. Homobrassinolide was administered (66 and 330ng/ Kg body weight) intradermally in male albino wistar strain rats and changes in alkaline phosphatase and creatine kinase activities were measured. An overall reduction in both the enzyme activities occurred within 2hr of administration with few exceptions. The reaction rate constants for the enzyme activities were in the order 10-7 mM/min for alkaline phosphatase and 10-3 mM/min for creatine kinase. Time course studies indicated a decrease in enzyme activities as a function of time. Elevated hemoglobin content correlated with rise in erythrocyte number. Blood glucose level decreased by a percentage of 15.7 and 21.7 compared to control with the administration of 10μg and 50μg homobrassinolide respectively. Serum cholesterol content showed 15% decrease and 25% increase compared to control following 10μg and 50μg homobrassinolide administration. We conclude that homobrassinolide inhibited both the enzymes in the tissues and produced erythrocytosis, leukocytosis and hypoglycemia, while cellular phosphorylation status remained principally affected by this oxysterol in rat. Even though the physiological and pathological significance of these observations is not clear, it is suggested that 28-HB enriched diets may not be appropriate for higher energy related work activities.Keywords: Alkaline phosphatase; Creatine kinase; Homobrassinolide; Oxysterol; Phosphorylation; Rate constant
