Maturation of early-phase insulin release in the neonatal lamb

Standardized primed continuous glucose infusions were performed in 13 newborn lambs between 4 h and 2 weeks of age to assess the timing of development of glucose-induced early-phase insulin release. Lambs of less than 6 h of age behaved similar to those previously infused in utero, with no early response noted. In contrast, early-phase insulin release was present in lambs of 12 h of age and older. Although basal plasma glucose rose with increasing post-natal age, this rise was not sufficient to account for the appearance of early phase insulin release. Factors other than the basal glucose level or the birth process itself may be operative.