The effect of thyroxine and thiouracil on the composition of milk. 1. The partition of phosphorus in cow milk in relation to phosphatase and other constituents

Publisher Website
Google Scholar
Abstract
Thiouracil injn. increased the phosphatase titer. Comparison of the rates of change of phosphatase after thyroxine or thiouracil injns. showed that 20 mg. thiouracil gave an increase of the same magnitude as the decrease caused by 10 mg. thyroxine. Milking at frequent intervals during 24 hrs. showed that 2 hrs. after a normal evening milking there is a pronounced max. in the phosphatase titer of cows treated with thiouracil. Neither thyroxine nor thiouracil affected the partition of N between casein, albumin, globulin, proteose-peptone and non-protein N. Thyroxine increased while thiouracil decreased the content of P of the milk. Thyroxine decreased while thiouracil increased the ratio of total N to total P in the milk. Thyroxine increased ester P markedly and also increased lipid P and caused a transient increase in casein P, partly at the expense of inorganic P. Thiouracil affected the partition of P in the milk in exactly the opposite way to thyroxine. As a result of changes in phosphatase and P partition there were negative correlations between phosphatase on the one hand and ester P and lipid P on the other. Inorganic phosphate was positively correlated with phosphatase; large negative coeffs. of correlation between ester P and phosphatase were found in untreated cows and in the exptl. cows before treatment. These coeffs. became larger under the influence of either drug. It is suggested in the light of this and earlier expts. that the effect of thyroxine in increasing the metabolic rate may be due to an increase of the phosphorylating enzymes in the tissues.