Colocalization of GH, TSH and prolactin, but not ACTH, with ?LH-immunoreactivity: evidence for pluripotential cells in the ovine pituitary

Abstract

Increasing evidence suggests that multihormonal cells in the pituitary gland may be more commonplace than previously thought. This has forced us to reconsider our classical view of cell populations in the pituitary gland. Studies so far have focused almost exclusively on the rat, and there is a dearth of information on other species. Our first objective was to determine whether a subpopulation of gonadotropes also express somatotropin in the ewe, as reported in the rat. In addition, we sought to determine whether gonadotropes express any of the other known pituitary hormones. Finally, we investigated whether the stage of the estrous cycle influenced the occurrence of these pluripotential gonadotropes. We found that a small population of betaLH-immunoreactive cells also expresses immunoreactive GH, prolactin and TSH. No gonadotropes colocalized with ACTH. Significantly (P<0.001) more gonadotropes expressed GH during the luteal (10.7+/-0.4%) than the late follicular (5.4+/-0.3%) phase but there was no difference between the luteal and follicular phases in the proportion of gonadotropes expressing prolactin (follicular: 5.7+/-0.7%; luteal: 5.5+/-0.6%) or TSH (follicular: 3.1+/-0.7%; luteal: 4.2+/-0.5%). Similarly, there was a significant (P<0.05) difference in the proportion of GH-immunoreactive cells expressing betaLH immunoreactivity in the luteal (5.9+/-0.3%) and follicular (3.4+/-0.5%) phases but no difference in the proportion of prolactin- (follicular: 2.2+/-0.7%; luteal: 2.0+/-0.8%) or TSH-immunoreactive cells (follicular: 9.6+/-3.7%; luteal: 10.8+/-2.9%) expressing betaLH. The specific function of these multihormonal gonadotropes in sheep remains to be determined.

Cells Co-Expressing Luteinising Hormone and Thyroid-Stimulating Hormone Are Present in the Ovine Pituitary Pars Distalis but Not the Pars Tuberalis: Implications for the Control of Endogenous Circannual Rhythms of Prolactin

“…This corroborates previous studies in BS ewes and in mice, and highlights a species difference in the prevalence of co-expression, as in contrast to sheep which showed a 10% co-expression in the PD [34], almost 41% of the mouse thyrotrophs were found to co-express LHB protein and secrete LH [35]. Whilst historically such cells are considered to represent an intermediate step in the trans-differentiation process, they are observed in the normal, resting gland where the rate of trans-differentiation is low.…”

Effect of nutrient restriction on the somatotropes and substance P-immunoreactive cells in the pituitary of the female ovine fetus

“…We have reported the specificity of the GH antibody previously [29]. The substance P antibody was preadsorbed with 10 lg/ml substance P (American Peptide Co, Sunnyvale, CA) and no staining was evident (data not shown).…”

Photoperiod-dependent effect of inflammation on nocturnal gene expression of proinflammatory cytokines and their receptors in <i>pars tuberalis</i> of ewe

“…The PT-specific secretory cells contain a small number of secretory granules and aggregate or scatter glycogen particles (Morgan and Williams, 1996;Yasuo and Korf, 2011). It was established that gonadotrophs from the PT may contain and secrete some amount of the luteinizing hormone (LH) and follicle stimulating hormone (FSH) (Mignot and Skinner, 2005;PerezCastro et al, 2012). Colocalization of LH and other hormones like prolactine, growth hormone (GH) and thyroid-stimulating hormone (TSH) was immunocytochemically demonstrated by Mignot and Skinner (2005).…”

“…It was established that gonadotrophs from the PT may contain and secrete some amount of the luteinizing hormone (LH) and follicle stimulating hormone (FSH) (Mignot and Skinner, 2005;PerezCastro et al, 2012). Colocalization of LH and other hormones like prolactine, growth hormone (GH) and thyroid-stimulating hormone (TSH) was immunocytochemically demonstrated by Mignot and Skinner (2005). Additionally, some studies showed that the PT can release factors which can modulate the activity of the PD lactotrophs (Lafarque et al, 2004).…”