title: Anterior pituitary hormone control by interleukin 2.
abstract: Several monokines, proteins secreted by monocytes and macrophages, alter release of hormones from the anterior pituitary. We report here the ability of femtomolar concentrations of interleukin 2 (IL-2), a lymphokine released from T lymphocytes, to alter directly pituitary hormone release. The effects of concentrations of IL-2 ranging from 10(-17) to 10(-9) M on anterior pituitary hormone release were evaluated in vitro. Hemipituitaries were preincubated in 1 ml of Krebs-Ringer bicarbonate buffer (KRB) followed by incubation for 1 or 2 hr with KRB or KRB containing different concentrations of IL-2. This was followed by incubation for 30 min in 56 mM potassium medium to study the effect of pretreatment with IL-2 on subsequent depolarization-induced hormone release. Prolactin (PRL), luteinizing hormone (LH), follicle-stimulating hormone (FSH), corticotropin (ACTH), growth hormone (GH), and thyrotropic hormone (TSH) released into the incubation medium were measured by radioimmunoassay. IL-2 stimulated the basal release of PRL at 1 or 2 hr but suppressed the subsequent depolarization-induced PRL release, perhaps because the readily releasable pool of PRL was exhausted. The minimal effective dose (MED) was 10(-15) M. Conversely, IL-2 significantly suppressed the basal release of LH and FSH at 1 or 2 hr, with a MED of 10(-16) M, thus demonstrating a reciprocal action of the cytokine on lactotrophs and gonadotrophs. The subsequent depolarization-induced release of LH and FSH was suppressed, indicative of a persistent inhibitory action of IL-2. IL-2 stimulated ACTH and TSH release at 1 hr and the MEDs were 10(-12) and 10(-15) M, respectively. Conversely, IL-2 significantly lowered the basal release of GH at 1 hr, with a MED of 10(-15) M. The release of GH was not altered at 2 hr. The high potassium-induced release of ACTH, TSH, and GH was not affected. The results demonstrate that IL-2 at picomolar concentrations affects the release of anterior pituitary hormones. This cytokine may serve as an important messenger from lymphocytes exerting a direct paracrine action on the pituitary by its release from lymphocytes in the gland or concentrations in the blood that reach the gland may be sufficient to activate it.
authors.affiliation: Department of Physiology, University of Texas Southwestern Medical Center, Dallas 75235-9040.
authors.forename: S
authors.initials: S
authors.lastname: Karanth
authors.forename: S M
authors.initials: SM
authors.lastname: McCann
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000818:Animals; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D013006:Growth Hormone / Q000378:metabolism; D066298:In Vitro Techniques; D007376:Interleukin-2 / Q000494:pharmacology*; D007700:Kinetics; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D010908:Pituitary Hormones, Anterior / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011994:Recombinant Proteins / Q000494:pharmacology; D013972:Thyrotropin / Q000378:metabolism
chemical_list: D007376:Interleukin-2; D010908:Pituitary Hormones, Anterior; D011994:Recombinant Proteins; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D013972:Thyrotropin; D013006:Growth Hormone