The influence of dietary methionine on the amino acid pool ofHymenolepis diminutain the rat's intestine

Abstract

The amount of [14C]methionine in the stomach, anterior and posterior intestine wall and lumen, blood and caecum of a rat, and in the anterior and posterior parts of the tapeworm Hymenolepis diminuta in the intestine, was measured at intervals from 10 min to 10 h after feeding a meal of 2 g glucose and 37.5 mg methionine by stomach tube.Nearly all the meal left the stomach within 5 h; the amount entering the tapeworm depended on the position of the worm. That part lying in the anterior half of the intestine was subjected to a rapid influx reaching a maximum concentration of at least 8 mM within 1–3 h after the meal was administered. The level in the worm then dropped to about 20 % of the peak level, although the stomach was still emptying and the level of methionine in the intestine wall was still rising. This was a stable state, and equal to the concentration in the posterior part of the worm which was reached 2 h after the rat was fed.The reason why the anterior part of the worm should show a big influx and efflux is discussed and related to changes in concentration of methionine in the lumen. The lack of such a flux into and out of the worm further down the intestine is related to the host's homeostatic control of amino acid balance in the intestine.The results prove that dietary imbalance of amino acids affect the amino acid pool in a tapeworm for about 3 h, if it lies in the anterior of the gut. A dietary regime is suggested which should produce a prolonged effect and thereby retard growth of the worm.The weights of the parts of the worms found in the anterior and posterior half of the small intestine revealed an unexpected phenomenon; the majority of the tapeworm, by weight, lies in the anterior of the intestine for about 4 h following a meal, but in the posterior of the intestine after the stomach has emptied.It is a great pleasure to thank Miss Gillian Moore and Miss Patricia Grant for technical assistance, and Shell International Petroleum Company, London, for financial support.