John W. Holaday

Exposure to bacterial endotoxins has long been known to stimulate the release of anterior pituitary hormones; administration of endotoxin was at one time a common clinical test of anterior pituitary function. Endotoxin is a potent stimulus for production of the endogenous pyrogenic protein, interleukin-1 (IL-1), by macrophages and monocytes. The possibility that IL-1 has a direct effect on the secretion of hormones by rat pituitary cells in a monolayer culture was investigated. Recombinant human IL-1β stimulated the secretion of adrenocorticotropic hormone, luteinizing hormone, growth hormone, and thyroid-stimulating hormone. Increased hormone secretion into culture supernatants was found with IL-1 concentrations ranging from 10 -9 M to 10 -12 M . Prolactin secretion by the monolayers was inhibited by similar doses. These concentrations of IL-1 are within the range reported for IL-1 in serum, suggesting that IL-1 generated peripherally by mononuclear immune cells may act directly on anterior pituitary cells to modulate hormone secretion in vivo. Incubation of IL-1 solutions with antibody to IL-1 neutralized these actions. These pituitary effects of IL-1 suggest that this monokine may be an important regulator of the metabolic adaptations to infectious stressors.

Opiates are among the oldest pharmacological substances known to man; their analgesic, euphoric, and addictive effects have been traditional focal points for opiate research. Without doubt, the cardiovascular effects of opiates have also been apparent to the user or abuser of opiate substances for several centuries. Persons seeking analgesic, euphoric, or antidiarrheal actions from opiate alkaloids have probably noted dizziness upon sudden st,anding due to the orthostatic hypotension these substances produce. His­ torically, however, scientific study on the cardiovascular responses to ad­ ministered opiates has lagged behind other areas of opiate research. This is understandable as, relative to doses required for their analgesic actions in humans, the cardiovascular effects of opiates are less noticeable and, indeed, undesirable. Early studies established that cardiovascular responses to morphine var­ ied among species; both autonomic and histamine-releasing properties con­ tributed to their hypotensive and bradycardic actions (1-5). Generally speaking, morphine was shown to produce prominent effects upon brain­ stem and hypothalamic centers that resulted in increased parasympathetic and decreased sympathetic tone (3-6). These effects upon autonomic out­ flow caused a depression of both heart rate and blood pressure. A resurgence of interest in opiate-cardiovascular interactions followed the discovery of endogenous opiate systems (for review see 7). A family of opioid peptides were found to be located at sites suggesting an autonomic action (8); also, opiate receptors were shown to be densely distributed in the brainstem and hypothalamus in close proximity to cardiovascular centers as well as endogenous opiate pathways (9, to). These anatomical findings

The effects of prolactin on lactation and reproductive organs are well known. However, the other possible target organs and physiological consequences of altered levels of circulating prolactin remain poorly understood. In this study, mice were treated with bromocryptine, a dopamine receptor agonist that inhibits pituitary prolactin secretion. Bromocryptine treatment prevented T-cell-dependent induction of macrophage tumoricidal activity after the intraperitoneal injection of Listeria monocytogenes or Mycobacterium bovis. Coincident treatment with ovine prolactin reversed this effect. Of the multiple events leading to macrophage activation in vivo, the production by T-lymphocytes of gamma-interferon was the most impaired in bromocryptine-treated mice. Lymphocyte proliferation after stimulation with mitogens in vitro was also depressed in spleens of bromocryptine-treated mice, and coadministration of prolactin also reversed this effect. Bromocryptine treatment also reduced the number of deaths resulting from inoculation of mice with Listeria; exogenous prolactin significantly reversed this effect. The critical influence of pituitary prolactin release on maintenance of lymphocyte function and on lymphokine-dependent macrophage activation suggests that, in mice, lymphocytes are an important target tissue for circulating prolactin.