Function of prolactin cells in the individual rat pituitary gland is location dependent

Mukherjee, Pinku; Salada, T.; Hymer, Wesley C.

doi:10.1016/0303-7207(91)90257-s

Cited by 16 publications

(6 citation statements)

References 24 publications

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“…Likewise, lactotropes which altogether lack innervation synthesize PRL at different rates (Walker and Farquhar, 1980), and hormone release is dependent on differential responsiveness to dopamine (Luque et al, 1986) and TRH (Walker and Farquhar, 1980). A predisposing factor for lactotrope heterogeneity may be their region of origin within the anterior lobe, possibly reflecting differing hypophysiotropic input (Boockfor and Frawley, 1987;Mukherjee et al, 1991). Thus, there are several avenues for control of melanotropes: synaptic transmission, classic endocrine regulation, and nonsynaptically released inhibitory transmitters acting by mechanisms similar to ''parasynaptic'' (Schmitt, 1984) or ''volume'' (Agnati et al, 1995) transmission.…”

Section: Discussionmentioning

confidence: 98%

Differential innervation of individual melanotropes suggests a role for nonsynaptic inhibitory regulation of the developing and adult rat pituitary intermediate lobe

Chronwall

Sands

Cummings

et al. 1998

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Dopamine and GABA were detected in intermediate lobe axons around birth, and early axons were closely apposed to glial cells and processes, possibly using them for guidance. In the adult, axons containing colocalized dopamine and GABA were distributed in a distinct pattern within the lobe, with plexuses located dorsally and ventrally. Axons preferentially followed glial processes in interlobular septa, yet were also interspersed between melanotropes. Individual melanotropes were contacted by varying numbers of axon terminals, with some devoid of contacts. Boutons contained both small clear vesicles and large dense-cored vesicles; membrane specializations were not well-developed. From these findings we concluded that in addition to direct synaptic inhibition, dopamine and GABA could stimulate their receptors by mechanisms similar to "parasynaptic" [Schmitt (1984) Neuroscience, 13:991-1001] or "volume" [Agnati et al. (1995) Neuroscience, 69:711-726] transmission as proposed for the CNS. Humoral agents passing into the intermediate lobe from portal vessels, thus acting as classical hormones, further regulate the melanotropes. Moreover, approximately 50% of the axonal elements were closely apposed to glia, suggesting that glia could have regulatory roles. Previous studies from our laboratory [Chronwall et al. (1987) Endocrinology, 120:1201-1211; Chronwall et al. (1988) Endocrinology, 123:1992:1202] demonstrated heterogeneity in proopiomelanocortin (POMC) biosynthesis among individual melanotropes, prompting the hypothesis that the degree of innervation could govern the expression of certain molecules. We combined immunohistochemistry and in situ hybridization histochemistry to evaluate whether melanotrope molecular heterogenity is spatially correlated with axons and terminals. Tentatively, melanotropes expressing low levels of POMC and alpha1A subunit P/Q type Ca2+ channel mRNAs often were apposed to axons, whereas those with low levels of D2L receptor mRNA rarely were contacted by axons, suggesting that innervation could be one of the factors inducing and maintaining heterogeneity.

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Section: Discussionmentioning

confidence: 98%

Differential innervation of individual melanotropes suggests a role for nonsynaptic inhibitory regulation of the developing and adult rat pituitary intermediate lobe

Chronwall

Sands

Cummings

et al. 1998

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“…Some studies in several species have related cell distribution in the PD parenchyma with blood irrigation and factors or hormones that control the activity of the adenohypophyseal cells under different physiological conditions (Sasaki and Iwama, 1988; Sato et al, 1999; Lee et al, 2004). Mukherjee et al (1991) have reported in rat that the functional heterogeneity among lactotrophs with regard to their regional distribution within the anterior lobe and their responsiveness to different secretagogues. In addition, Vitale et al (2001) have reported that in mink the synchronization of the cellular activity inside the follicles contributed to the control of the PRL secretion during the reproductive period.…”

Section: Discussionmentioning

confidence: 99%

Morphological and Morphometric Changes of Pituitary Lactotrophs of Viscacha (Lagostomus maximus maximus) in Relation to Reproductive Cycle, Age, and Sex

Filippa

Mohamed

2009

The Anatomical Record

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Lactotrophs in pituitary pars distalis (PD) of viscacha were studied by immunohistochemistry and morphometric analysis in the following groups: 1) adult males throughout the reproductive cycle (reproductive, gonadal regression, and recovery periods), 2) melatonin-treated adults, 3) castrated adults, 4) prepubertal, 5) non-pregnant females, and 6) pregnant females (early, mid, and late pregnancy). Immunopositive percentage area (%IA), cell percentage in PD (% PDC), number of cells per reference area (no.cell/ RA), major cellular and nuclear diameters were analyzed. Lactotrophs were mainly localized in the ventro-medial region and the caudal extreme of PD. In the male viscachas, they were isolated in small and big groups, close to blood vessels and near follicles. These cells were pleomorphic and with a heterogeneous cytoplasmic immunolabeling pattern. In the adult males of the gonadal regression period the morphometric parameters were the lowest. Most parameters of lactotrophs in the prepubertal were significantly lower than in the adult males in the reproductive period. In the melatonintreated animals and in castrated animals there was a decrease in %IA, %PDC, and no.cell/RA. In the females, the morphometric parameters increased at the end of pregnancy. Non-pregnant females exhibited a higher immunopositive area and number, but a smaller size of cells than males. Our results showed that in the adult male viscacha, lactotrophs vary seasonally, probably due to the photoperiod effect through melatonin. Besides the changes observed after castration, in prepubertal animals, in adults of different sex, and during pregnancy suggest that the gonadal steroid hormones might modify the lactotrophs activity. Anat Rec, 293:150-161, 2010. V V C 2010 Wiley-Liss, Inc.

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“…Two regions have been delineated, viz. an "inner" zone in the vicinity of the neurointermediate lobe and an "outer" zone en-compassing the periphery of the gland (Boockfor and Frawley 1987;Sasaki and Iwama 1988;Mukherjee et al 1991;Nagy et al 1991;Porter and Frawley 1992;Hu and Lawson 1994). Such regional differences in the responsiveness to thyrotropin-releasing hormone (TRH) and dopamine have been observed in the lactating female rat (Boockfor and Frawley 1987;Nagy et al 1991).…”

Section: Introductionmentioning

confidence: 99%

Structural and functional differences between prolactin cells from the inner and outer zones of the male rat anterior pituitary

Vila-Porcile

Barret

1996

Cell and Tissue Research

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The aim of this study was to compare the ultrastructure of prolactin cells in the inner and outer zones of the male rat anterior pituitary, and to relate their morphological features to their secretory activity, by means of standard and ultrastructural reverse hemolytic plaque assays (RHPA). The immuno-ultrastructural study showed that in the inner pituitary small-granulated cells represented 52% of the prolactin cells, there being only 5% with large granules, whereas the prolactin cells with large granules accounted for 52% in the outer zone, with only 7% being small-granulated. Percentages of cells with intermediate-sized granules were 43% and 41%, respectively. Analysis of RHPA data revealed that, under basal conditions, prolactin cells secreted more actively in the inner zone than in the outer zone. Stimulation with thyrotropin-releasing hormone or KCl treatment increased the percentage of secretors and the sizes of hemolytic plaques in both zones. However, in response to thyrotropin-releasing hormone, the increase in number of secretors was always higher in the outer zone, whereas the enlargement of plaque sizes was greater for the "inner" cells. These findings are in favor of the small-granulated cells, which predominate in the inner zone, being in a stage of active secretion and responsiveness.

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Function of prolactin cells in the individual rat pituitary gland is location dependent

Cited by 16 publications

References 24 publications

Differential innervation of individual melanotropes suggests a role for nonsynaptic inhibitory regulation of the developing and adult rat pituitary intermediate lobe

Differential innervation of individual melanotropes suggests a role for nonsynaptic inhibitory regulation of the developing and adult rat pituitary intermediate lobe

Morphological and Morphometric Changes of Pituitary Lactotrophs of Viscacha (Lagostomus maximus maximus) in Relation to Reproductive Cycle, Age, and Sex

Structural and functional differences between prolactin cells from the inner and outer zones of the male rat anterior pituitary

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