Development of pituitary gonadotropic cells in the pig fetus and the effect of luteinizing hormone-releasing hormone administration.

Pituitary gonadotropic development in fetal pigs has been studied immunocytochemically. From 50 days postcoitum (p.c.) until 90 days p.c. the volume density of luteinizing hormone (LH) immunoreactive cells increased from 0.12% to 0.61% of the glandular mass of the anterior part of the pituitary gland. From 90 to 100 days p.c. a steep increase to 4.5% was found. A single injection of long-acting luteinizing hormone-releasing hormone (LHRH) to the fetus at 75 days p.c. inhibited this developmental pattern. Pulsatile administration of LHRH agonist to fetuses from 70 to 73 days p.c. had no significant effect on the volume density of LH immunoreactive cells, whereas pulsatile administration from 70 to 80 days p.c. and from 95 to 105 days p.c. inhibited the normal increase of this parameter. It is concluded that from 70 days p.c. onwards the development of fetal gonadotropic cells can be manipulated by exogenous LHRH.