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Passive uptake in the small intestine and active uptake in the hindgut contribute to the highly efficient mineral metabolism of the common mole-rat, Cryptomys hottentotus

Published online by Cambridge University Press:  09 March 2007

Tammy Pitcher  and
Rochelle Buffenstein
Tammy Pitcher
Affiliation:
Physiology Department, Medical School of the University of the Witwatersrand, 7 York Road Parktown, 2193, South Africa
Rochelle Buffenstein
Affiliation:
Physiology Department, Medical School of the University of the Witwatersrand, 7 York Road Parktown, 2193, South Africa
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Abstract

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Cryptomys hottentotus has no access to dietary or endogenous sources of cholecalciferol (D3). Serum concentrations of calcifediol (25(OH)D3) were undetectable (< 5 ng/ml) and calcitriol (1,25(OH)2D3), although detectable in plasma, was at a low concentration (31.40) (SEM 3.06 pg/ml). Despite their naturally impoverished vitamin D status, these animals exhibited highly efficient mineral absorption processes (Ca apparent fractional absorption efficiency, AFA (%) 95.33 (SEM 1.36); inorganic P (Pi) AFA (%) 93.49 (SEM 0.81)). Furthermore, plasma mineral content was tightly regulated (Ca 2.57 (SEM 0.08) mmol/l; Mg 1.23 (SEM 0.05) mmol/l; Pi 2.12 (SEM 0.15) mmol/1). Mode of uptake in C. hottentotus was unlike that in other D3-replete mammals. First, passive (rather than active) uptake occurred in the traditional site of active Ca absorption (with serosal: mucosal (S:M) ratios in the duodenum of 1.32 (SEM 0.13)), and the only site of active Ca uptake was the hindgut (caecum S:M 3.35 (SEM 0.46); proximal colon S:M 2.13 (SEM 0.30)). Despite the presence of active uptake in these hindgut regions, their overall contribution to the daily rate of mineral absorption was small (9.53 (SEM 1.27)%). These underground inhabitants rely upon highly efficient, passive mineral uptake. This is adequate to meet their mineral requirements and maintain mineral homeostasis in the absence of vitamin D.

Keywords

Mineral metabolismCalciumMole-rat
Type
Absorption of mineral in the hind gut
Information
British Journal of Nutrition , Volume 71 , Issue 4 , April 1994 , pp. 573 - 582
Copyright
Copyright © The Nutrition Society 1994

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