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Short Term Neonatal Starvation Altered Cholera Toxin Binding in Rabbits¹

Pediatric Gastroenterology and Nutrition, University of Massachusetts Medical Center, Worcester, MA 01655 ^* Combined Program in Gastroenterology and Nutrition, Children's Hospital and Massachusetts General Hospital, Boston, MA 02115

Acute neonatal malnutrition alters lumenal glycoproteins as demonstrated by altered lectin binding. To determine the effect of a 72-h fast on lumenal glycolipids, specifically the monosialogangloside G_M1, we quantitated cholera toxin (CT) binding and adenylate cyclase activity. The calculated number of specific sites for CT binding to microvillus membrane (MVM) from newborn rabbits fasted for 72 h was decreased in MVM from proximal small bowel (7 ± 0.8 x 10⁸/µg protein) compared to 72-h control neonatal rabbits (18 ± 3.3 x 10⁸/µg protein). In distal small bowel there was no difference in the calculated receptor sites/µg MVM protein between fasted (8 ± 1.7 x 10⁸) and fed (11 ± 4 x 10⁸) groups. MVM prepared from proximal small bowel of fed animals bound significantly more CT than MVM prepared from distal small bowel of fed animals. The affinity for CT was the same in all MVM preparations. Neuraminidase treatment of MVM resulted in increased CT binding in fed and fasted rabbit proximal and distal MVM preparations, but the greatest increase occurred in MVM prepared from proximal small bowel from fasted animals. There was no difference in adenyiate cyclase activity in fed, fasted, and proximal or distal small bowel crude membrane preparations. Refeeding (120 h) resulted in normalization of CT binding in MVM from proximal small bowel of fasted animals. We conclude a 72-h fast in neonatal rabbits resulted in decreased regional CT binding in MVM prepared from proximal small bowel of fasted animals, but no change in adenylate cyclase activity. Refeeding reverses CT binding abnormalities.

KEY WORDS: • neonatal malnutrition • gastrointestinal mucosa • microvillus membrane • cholera toxin binding

¹ Supported by a grant from the Charles H. Hood Foundation and US Department of Agriculture Research Grant #85-00941 to Susan Baker and by National Institutes of Health Research Grants P01-AM33506, P01-HD20810, R01-DK37521, R01-HD12437 to W. Allan Walker.

Manuscript received 15 April 1988. Revision accepted 27 October 1988.