Absorption and retention of dam's milk calcium in suckling mice

Abstract

Distribution of the radiocalcium was measured in mother mice and suckling young by parenteral administration of 45Ca into the dam. Seventeen lactating mice (9 CFW and 8 C57BL/6) were used in this study. Each litter size was adjusted to 5 on the 5th day of lactation. On the 12th day of lactation, the young were removed from the dam for 3 hours from 9:00 A. M. to noon. The dam was intraperitoneally injected with 45Ca at 11:00 A. M. and one hour later 5 young were allowed to suckle the dam for 1 hour from noon to 1:00 P. M. One young each selected randomly from each one of the dams was killed at 1:00 P. M. 1:30 P. M. 2:00 P. M. 3:00 P. M. and 4:00 P. M. Carcass of the young was divided into three parts, i. e., stomach, intestine and the rest of the body.
(1) Average body weight of 85 young at the end of suckling was about 6.0g. Fresh weight of the young stomach was the highest (181mg) immediately after the suckling and it gradually decreased to 76mg during the 3 hour period, while there was no fluctuation in the weight of the intestine.
(2) Radiocalcium content of the young stomach at the end of suckling was 5.3% of the 45Ca administered and it linearly decreased to 1.5% during the 3 hour period. At the end of the 1 hour-suckling period, the young already retained 1.6% of 45Ca in the body, and the retention linearly increased to 5.4% during the following 3 hours. Radiocalcium content of the intestine was low and kept constant (0.3%) throughout the experimental period. These results indicate that calcium in milk is effectively absorbed and largely retained by the suckling young in the short period.
(3) About 36% of 45Ca injected into the dam was transferred to 5 suckling young through milk during the 1 hour-suckling period, and it was extremely higher than the 45Ca content in the dam's femur.