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.