Milk Factors Controlling the Plasma Calcitonin Level in the Newborn Rat*

Abstract

The elevated plasma calcitonin (CT) levels found during suckling in the newborn rat, in contrast with the low or undetectable values found during fasting, prompted this investigation of the effect of milk constituents on plasma CT. Plasma concentrations of calcium, inorganic phosphorus, glucose, insulin, and CT were determined in 2-h-old newborns which had previously received (120, 90, 60, or 30 min before) by stomach gavage triglycerides, lactose, casein enzymatic hydrolysate, or calcium in physiological amounts. Triglycerides (20 mg in 0.2 ml) induced a rapid and sustained increase in plasma CT levels without change in plasma calcium. Blood glucose levels increased, but plasma insulin changed very little. A transient increase in plasma CT was observed 30 min after lactose administration (20 mg in 0.2 ml). This stimulation (∼2-fold rise) was, however, smaller than that observed after triglycerides (∼6-fold rise). Blood glucose and insulin both were markedly increased throughout the time course of the lac...