Ultrastructural observation of anterior pituitary gonadotrophs following hypophysial portal vessel infusion of luteinizing hormone-releasing hormone.

Luteinizing hormone-releasing hormone (LHRH) (50 ng) was infused with a microcannula into hypothalamo-hypophysial stalk portal vessels of adult male rats. Anterior pituitaries were prepared for electron microscopy at 1, 5, 10, 15, 30 and 60 minutes after infusion. Granule release (exocytosis) from gonadotrophs was stimulated within one minute. Evidence of increased protein synthesis began at 5-10 minutes but was not maximal until 15 minutes. The majority of new granules appeared in the Golgi apparatus at 15 and 30 minutes. This study provides morphological evidence for LHRH-induced hormone and synthesis release under physiological conditions.