Comparative Studies on the Adsorption of Vitamin B₁₂ to Intestinal Mucosa Homogenate of Adult and Unweaned Rats

Abstract

Studies on the Adsorption of Vitamin. B12 to Intestinal Mucosa Homogenate of Adult and Unweaned Rats. Tohoku J. exp. Med., 1971, 104 (3), [215][216][217][218][219][220][221][222][223] For the purpose of elucidat ing the physiological significance of intrinsic factor (IF) in vitamin B12 absorption, comparative studies on the adsorption of vitamin B12 to intestinal mucosa homogenate of unweaned (aged 48 hours old) and adult rats were carried out. Any material having IF activity on the intestine of the adult rat and the unweaned rat was not secreted from the stomach of the unweaned rat. This result was confirmed by the histologic findings that the chief cells of the unweaned rat, when examined on the fundus portion of the stomach, were still undeveloped. The adsorption of vitamin 13.2 to the intestinal mucosa homogenate of the unweaned rat seemed to be independent on the IF and the presence of Ca++ ion. The amount of vitamin B12 adsorbed to intestinal mucosa homogenate of the unweaned rat, as expressed by jig vitamin B,,/kg body weight, was from 4 to 10 times larger than that of the adult rat. The high capacity of the intestinal mucosa homogenate of the unweaned rat to adsorb vitamin B12, regarded as the first step of vitamin B,2 absorption, may be related to the fact that unweaned rat can absorb a large amount of vitamin B12. The small intestine of the unweaned rat appears to take indiscriminately fairly large molecules. The results of the experiments which investigated the effects of bivalent cations on the adsorption of vitamin B12 to intestinal mucosa homogenate suggested that the so-called sequential uptake might have occurred.B12 absorption; intrinsic factor; unweaned rat It has been known that the absorption of vitamin B12 requires the aid of intrinsic factor (IF) in adult animals of many species. On the other hand, it was found by the experiments on intestinal segments that the small intestine of the unweaned rat can take vitamin B12 without IF, and that any material having IF activity on the intestine of the adult rat is not secreted front the stomach of the unweaned rat (Boass and Wilson 1963). Recently Williams and Spray (1968) reported similar results from the experiments in vivo. They also found that rat's milk given with vitamin B12 did not affect the absorption.We have attempted to know whether the stomach of the unweaned rat secretes any material which has IF activity specifically on the intestine of the unweaned rat.Comparative studies were also made on the IF dependent vitamin B12 absorption in the adult rat and IF independent vitamin B12 absorption in the unweaned rat in

Change of the System for the Adsorption of Vitamin B₁₂ to Intestinal Mucosa Homogenate in Growing Rats

“…vitamin B1, absorption; intrinsic factor In our preceding papers (Yamada et al 1970(Yamada et al , 1971), we reported the results obtained by comparative studies on the adsorption of vitamin B12 to intestinal mucosa homogenates of adult and unweaned rats (48 hours after birth). The data obtained indicated that 1) stomach of the unweanded rats secreted neither intrinsic factor (IF) nor IF-like materials, 2) the amount of vitamin B12 adsorbed to the intestinal mucosa homogenates of the unweaned rats in the absence of IF was very high compared with that to the intestinal mucosa homogenates of the adult rats, and 3) adsorption of vitamin B12 to the intestinal mucosa homogenates of the unweaned rats was not significantly affected by the omission of bivalent cations from the incubation medium.…”