Regulation of luteinizing hormone in the fetal and neonatal lamb. I. LH concentrations in blood and pituitary.

Abstract

LH was studied in 504 lambs during the last two-thirds of prenatal development through day 18 of postnatal life using specific and sensitive radioimmunoassays to quantitate LH in small amounts of sera and anterior pituitaries. The increase in both pituitary LH concentration and gonadal weight with fetal age was greater for males than females. Despite the elevated concentrations of LH in the fetal pituitary during the final third of gestation, circulating LH in both sexes decreased to the lowest levels observed during fetal life. However, these changes in pituitary and serum LH concentrations during prenatal development were different for the two sexes but seemed unrelated to the differential growth of the gonads. Although the concentration of LH in fetal serum was not influenced by the presence of a twin, twins of either sex had a lower concentration of pituitary LH than singletons. The sex of the co-twin had no effect on this parameter. A precipitous decrease in pituitary LH occurred in lambs of both sex...