CHANGES IN JEJUNAL EPITHELIAL MORPHOLOGY & KINETICS DURING SUCKLING & WEANING IN THE CROWING GUINEA PIG

Abstract

Weaning, the nutritional adaptation from milk to solid diet, demands changes in Cl function. We measured jejunal mucosal morphology and kinetics during suckling and weaning to determine if the marked changes seen in the altricial rat also occur in the precocial guinea pig (CP). 79 animals mere studied. Croups of at least 3 CPs aged 1,7,14,21 and 28 d were given IP colchicine at time 0, and killed at 20 to 30 min intervals. Tissue was taken 5 cm from the pylorus, fixed and bulk stained with Schiff reagent. Jejunal morphology was measured by microdissection and crypt cell production rate (CCPR) by a metaphase arrest technique. There was 40% decline in villus ht, from 986 μm to 618 μm (p<0.001), and 25% increase in crypt depth, from 148 μm to 199μm (p<0.01), during the first 2 wks. After an initial decline there was an increase in crypt: villus (C;V) ratio from 6.7 to 8.2, and in CCPR from 3.9 to 5.6 cells/crypt/hr from 14 d onwards (pz0.001). These changes represent a proliferative response of jejunal epithelium during the 3rd & 4th postnatal weeks, accounted for by increase in the depth and number of crypts, and CCPR, leading to increase in net villus influx. In contrast with the rat in which abrupt changes in epithelial morphology, function and kinetics occur around d 21 at the time of cessation of suckling, in the CP they are gradual and follow weaning by some days. The CP, which in many respects more closely resembles man than rat, is a more suitable animal model for our understanding of human Cl maturation and perinatal nutritional adaptation.