Liver blood flow. metabolic heat production and body temperature before, during and after phenobarbitone administration.

Using an improved apparatus based on Grayson's principle of internal calorimetry, conductivity as a measurement of liver blood flow and metabolic heat production in the liver as a measurement of liver tissue metabolism were recorded in the conscious rat before, during and after phenobarbitone administration. In addition, rectal body temperature was measured under the same experimental conditions using an electronic thermometer. Liver blood flow increased by a mean of about 100% above control values in rats treated with phenobarbitone 30 mg/kg daily for 4 days. In contrast, changes in metabolic heat production showed no clear tendency and remained more or less constant. However, body temperature rose significantly during phenobarbitone administration up to 38.9% C and this temperature changes showed the same time course as liver blood flow and parameters of microsomal enzyme activity. Therefore it is suggested that metabolic heat production is not a very important factor in influencing the increase in liver blood flow following enzyme induction. On the other hand the increase in body temperature observed in the present study might be an important factor in influencing the increase in blood flow to the liver.