Intestinal hydrolytic activity in young mink (Mustela vison) develops slowly postnatally and exhibits late sensitivity to glucocorticoids

Abstract

The development of hydrolase activity in the intestinal brush border membrane is important for the maturation of digestive function in early life. The development and glucocorticoid control of intestinal enzymes were investigated in the mink (Mustela vison), a carnivorous species, in which the intestine matures relatively late in postnatal life. Mink kits (n = 110 from 20 litters) were either not treated or injected intramuscularly for 7 d with saline, adrenocorticotropic hormone [ACTH, 50 μg/(kg · d)] or cortisol 21 - acetate [synthetic glucocorticoid, 50 mg/(kg · d)]. The kits were killed at 2, 4, 6, 8 or 10 wk of age and the proximal, middle and distal intestine removed for analyses. Lactase activity was maximal at 4 wk and decreased to about 5% of this level during the following 2 wk. Cortisol treatment stimulated total lactase activity at 2 wk (170% that of controls, P < 0.05) and reduced this activity at 4 wk (20% that of controls, P < 0.001). Aminopeptidases N and A underwent their major developmental increases in activity at 4-6 wk and again, enzyme development was stimulated by cortisol. Other enzymes showed either a gradual increase (maltase), a slight decrease (dipeptidylpeptidase IV) or no consistent change (sucrase) in activity with advancing age from 2 to 10 wk, but the activities remained highest in cortisol-treated kits. Treatment with ACTH enhanced the activity of all enzymes at 2 wk but had little effect thereafter. Intestinal hydrolases develop later in the mink and are sensitive to glucocorticoid induction for a longer period in postnatal life than in species such as rats, pigs or humans. The mink is a useful model in studies of the regulatory mechanisms which influence the development of intestinal brush border hydrolases.