title: The development of the pituitary-adrenal axis in the guinea pig.
abstract: The concentration of cortisol and ACTH in the umbilical vein plasma of the foetal guinea pig has been measured over the later half of gestation. Between 55--60 days there is a large increase in the concentration of both. Injection of ACTH1-24 into the foetal guinea pig elicits a relatively small increase in plasma cortisol at 46--55 days, a somewhat greater response at 56--60 days and a large response at 61--66 days. Between 47--55 days and 58--63 days cells prepared from the foetal adrenal show a large increase in their responsiveness to ACTH stimulation as measured by cortisol and androstenedione output. However, there was no clear difference in responsiveness between 58--60 days and 61--63 days. Thus between 56--60 days the foetal adrenal appears less responsive to ACTH stimulation in vivo than in vitro. ACTH in the circulation of the guinea pig is present in high-molecular-weight and low-molecular-weight forms and the ratio of concentration of ACTH1-39 to that of the high-molecular-weight forms rises after 60 days. It is proposed that this is an important factor in inducing an increased steroid response from the foetal adrenal.
mesh_terms: D000311:Adrenal Glands / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000494:pharmacology; D000735:Androstenedione / Q000378:metabolism; D000818:Animals; D004967:Estrogens / Q000096:biosynthesis; D005260:Female; D005312:Fetal Blood / Q000032:analysis; D005865:Gestational Age; D006168:Guinea Pigs; D006854:Hydrocortisone / Q000097:blood / Q000378:metabolism; D066298:In Vitro Techniques; D010913:Pituitary-Adrenal System / Q000196:embryology*; D011247:Pregnancy; D011453:Prostaglandins / Q000096:biosynthesis
chemical_list: D004967:Estrogens; D011453:Prostaglandins; D000735:Androstenedione; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone