Intestinal absorption and turnover of dl-methionine during reproduction in the rat.

Abstract

Absorption of dl-methionine from the rat intestine was studied during different stages of reproduction. Radiomethionine was introduced into the intestinal lumen of anaesthetized animals and, after a thirty minute period when the fluid remained in the intestine, was collected and its activity was detected. Blood samples were taken from the portal vein at 10th, 20th and 30th minutes. Samples were prepared from the liver and the mammary gland parenchyma as well, and their radioactivity was similarly determined. Methionine and cystine content in liver and mammary gland parenchyma tissue was examined by paper-chromatography.The results indicate that there is an increased absorption of the labelled methionine from the small intestine in the second and third week of lactation. At the 21st day post partum, the rate of absorption have returned to almost the normal values of the controls. The increase in utilization of methionine goes parallel with the increase of “tissue demands” for this amino acid. Thus the requirement of the mammary gland parenchyma for methionine be comes more evident in the second and third week post partum than is observed during pregnancy or early in lactation. The accelerated turnover of radiomethionine is supported by the rapid conversion of methionine into cystine in liver as well as mammary gland parenchyma.No significant incorporation of radiosulphur was noted in the liver, however, the biological half life time of methionine in the portal blood proved to be considerable less than that of the control cases. The results may relate to the functional adaptation of the lactating organism to meet the higher demands for methionine supply under the conditions of the increased food intake.