Ontogeny of tissue and serum gastrin concentrations in fetal and neonatal sheep.

We investigated the perinatal ontogenic changes in ovine serum and tissue gastrin concentration. Fetal and maternal serum gastrin levels in serums obtained from indwelling catheters in the fetal and maternal circulations and tissue gastrin levels were assessed by radioimmunoassay and immunohistochemistry. Fetal serum gastrin concentration was undetectable until the 107th day of gestation and significantly increased to levels surpassing maternal values. Neonatal serum hormone concentration continued to rise, reaching a peak during the 4th postnatal wk and decreasing after the 4th wk coincident with weaning. Maternal serum gastrin concentration did not vary during pregnancy and did not correlate with fetal serum gastrin levels. Fetal abomasal and duodenal gastrin concentrations and abomasal G-cell number increased in parallel with the developmental alterations in fetal serum hormone levels during gestation. The developmental increase in abomasal gastrin concentration was not associated with a shift in the molecular form of the hormone. These findings support the hypothesis that circulating gastrin in the fetus is of fetal origin.