PMC

Morphological adaptation in the digestive organs during lactation
Wet mass of the small intestine, caecum and large intestine during two reproductive states (virgin and lactating) of Swiss-Webster mice. Here and in subsequent figures error bars denote standard error of the mean. Asterisks here and in denote results differ significantly between the two reproductive states. Note the lactating mice have significantly larger (P < 0.05, n = 8) absorptive organs than virgin mice, using ANCOVA with body mass as the covariate. (The same trend is true for dry organ masses.)

Load and capacity of maltase and SGLT1 at different caloric requirements
Comparisons of maltase capacity, SGLT1 capacity and their respective functional loads of maltose (in the direct form of dietary maltose) and glucose (after hydrolysis of dietary maltose by maltase). Dietary maltose load (mmol day⁻¹) equals the product of dietary intake (g day⁻¹) times dietary maltose concentration (mmol g⁻¹); glucose load upon SGLT1 = 2 times the dietary maltose load; capacity = intestinal mass (mg) times protein activity (mmol day⁻¹ mg⁻¹). Glucose load on SGLT1 (left axis) is double the disaccharide load (right axis) on maltase because each maltose potentially yields two glucose molecules for transport by SGLT1. Note that, in each reproductive state (virgin and lactating) the maltase capacity considerably exceeds the SGLT1 capacity. Note also that maltase capacity increases by a smaller factor from virgin to lactating mice than does maltose load, and that SGLT1 capacity increases by a smaller factor than does glucose load, so that safety factors of both proteins decrease during lactation.

Morphological and functional response to lactation along the small intestine
Gradients of intestinal tissue mass (A) and brush-border maltase and glucose transporter (SGLT1) activities (B) along the small intestine of virgin and lactating mice. Ordinate units in B are nanomoles of glucose taken up by SGLT1 per minute per milligram of intestinal wet mass (left axis) and nanomoles of maltose hydrolysed by maltase per minute per milligram of wet intestinal mass (right axis). Data are means (n = 8 per treatment) ± s.e.m. Note that, in all three sections (proximal, medial and distal) of the small intestine, mass is significantly greater (P < 0.05) in the lactating than the virgin group (A), but that activities of both maltase and SGLT1 do not differ significantly (P < 0.05) between the two treatment groups (B). Because capacity = intestinal mass × protein activity, it is the increase of intestinal mass that accounts entirely for the increase of maltase and SGLT1 capacities during lactation (as seen in ).