Co-localisation of prostaglandin endoperoxide synthase and immunoreactive adrenocorticotrophic hormone in ovine foetal pituitary

Abstract

Previous studies have shown that both an intact hypothalamic-pituitary-adrenal axis and prostaglandin E 2 (PGE 2 ) are involved in the timing of parturition in sheep. PGE 2 is known to be synthesised by the placenta but has also been found in the foetal brain and pituitary. We propose that the enzymes necessary for production of PGE 2 are found in the ovine foetal pituitary and may be able to exert an autocrine and/or paracrine influence on corticotropes, resulting in an increased secretion of immunoreactive adrenocorticotrophin (irACTH). Pituitary tissues from foetal sheep, of gestational ages 119-126 days, were examined by immunohistochemistry. Primary antibodies for prostaglandin H synthase-1 and -2 (PGHS-1 and PGHS-2), microsomal prostaglandin endoperoxide synthase (mPGES) and irACTH were used to probe expressed proteins and Alexa-Fluor red-and green-fluorescent secondary antibodies were used to visualise the bound primary antibody. Staining for PGHS-1, PGHS-2 and mPGES was found throughout the foetal anterior pituitary. PGHS-1 and mPGES were widely distributed, including but not restricted to corticotropes. PGHS-2 was less widely distributed but occasionally was found in cells adjacent to corticotropes. The results indicate that locally produced prostaglandins may have an influence on the secretion of ACTH, independent of placental PGE 2 .

Mapping Acute Systemic Effects of Inhaled Particulate Matter and Ozone: Multiorgan Gene Expression and Glucocorticoid Activity

“…Moreover, MT-1 and MT-2, which exhibited systemic increases in response to pollutant exposure, are activated by glucocorticoids (Ghoshal et al ., 1998). The increase of PTGS2 mRNA, a critical activator of the HPA axis (Bugajski et al ., 2004; Reimsnider and Wood, 2004), by both particles and ozone, appeared to be additive, consistent with impacts on the HPA axis by both pollutants (Fig. 6A).…”

“…The mechanism by which pollutants activate the HPA axis is unknown. Prostaglandins play a key role in stimulating the HPA axis, and our expression data, showing increased expression of prostaglandin endoperoxide synthase 2 mRNA in the pituitary but not in other organs immediately after exposure, suggest that local production of prostaglandins in the pituitary (Bugajski et al ., 2004; Reimsnider and Wood, 2004) may be involved. Transit of particles or their soluble elements from the lungs to other organs, including the brain, has been described (Oberdörster et al ., 2004); ozone, on the other hand, is entirely consumed in the lungs, suggesting that actions are through intermediary signals rather than direct effects.…”

Blockade of Estrogen Receptors Decreases CNS and Pituitary Prostaglandin Synthase Expression in Fetal Sheep

“…Although we do not fully understand the physiological roles of PGHS-1 and -2 in the pituitary, we do suspect that one or both of these enzymes influences ACTH secretion. PGHS-1 expression is at least partially co-localized in corticotropes, and PGHS-2 expression is often found in cells adjacent to the corticotropes [35]. Brooks and Gibson have previously reported that PGE 2 enhances the ACTH response to AVP [36].…”

Obesity and Asthma

“…63 Some studies have suggested that inhaled pollutants may reach the brain and stimulate local production of prostaglandins in the pituitary. 64,65 Animal studies have shown that prenatal exposure to nicotine causes weight gain by disrupting the cholinergic and catecholaminergic systems. 66 Modulation of the sympathetic nervous system by the EDCs has been proposed to cause weight gain.…”