AJP - Endocrinology and Metabolism, Vol 263, Issue 5 E1002-E1009, Copyright © 1992 by American Physiological Society
In vivo estimation of lactose hydrolysis in premature infants using a dual stable tracer technique
C. L. Kien, K. Ault and R. E. McClead
Department of Pediatrics, Ohio State University, Columbus.
To investigate their putative capacity for lactose digestion, primed
continuous orogastric infusions of [1-13C]glucose and D-[1-13C]lactose were
administered on consecutive days to five premature infants (30-31 wk
gestation, 15-32 days of age), who were fed by orogastric infusions of
human milk or formula. By monitoring the plateau isotopic enrichment of
plasma glucose using isotopomers containing the entire derivatized glucose
molecule or C-2 through C-6, we were able to distinguish label appearing in
the peripheral circulation deriving from unmetabolized glucose from that
arising from recycled or fermented glucose (or lactose). Isotopic
enrichment of the C-1 of glucose, corrected for recycling, was then
calculated during each tracer infusion, and the fraction of dietary lactose
subjected to in vivo hydrolysis was estimated from these values and the
respective tracer infusion rates, assuming similar absorptive and metabolic
fates of labeled glucose arising from either tracer. This fraction averaged
1.02 +/- 0.16 (SD), suggesting that lactose digestion is efficient by 34-wk
postconceptional age.
