Ontogeny of intestinal safety factors: lactase capacities and lactose loads

Area of Science:

• Physiology
• Developmental Biology
• Gastroenterology

Background:

• Lactose digestion relies on intestinal capacities like lactase and Na+-glucose cotransporter (SGLT-1).
• Safety factors quantify the reserve capacity of physiological systems relative to demand.

Purpose of the Study:

• To measure intestinal safety factors for lactose digestion in developing rats.
• To assess the relationship between lactose load and the capacities of lactase and SGLT-1 during development.

Main Methods:

• Quantitative analysis of intestinal safety factors in rat pups at various ages (5, 10, 15, 30, and 100 days).
• Measurement of lactase and SGLT-1 capacities in relation to lactose load.
• Assessment of hindgut fermentation via gut morphology and hydrogen production assays in weanling and adult rats.

Main Results:

• Intestinal capacities for lactase and SGLT-1 increased with age in pups.
• Safety factors were high (8-13) in 5-day-old pups, decreasing to 4-6 by day 10/15.
• Adult rats (day 30 and 100) showed a safety factor of approximately 1.0 for SGLT-1, with evidence of hindgut fermentation as a reserve capacity.

Conclusions:

• Developing rat intestines exhibit high safety factors for lactose digestion, suggesting preparation for future demands.
• Safety factors decrease to adult levels by weaning, with hindgut fermentation compensating for reduced reserve capacity in adult rats.
• Lactase and SGLT-1 capacities develop in coordination throughout ontogeny and in response to varying lactose loads.