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Anatomical and functional gonadotrope networks in the teleost pituitary.

Golan M, Martin AO, Mollard P, Levavi-Sivan B - Sci Rep (2016)

Bottom Line: We found that in two fish species, namely tilapia and zebrafish, LH cells exhibit close cell-cell contacts and form a continuous network throughout the gland.These anatomical differences also manifest themselves at the functional level as evidenced by the effect of gap-junction uncouplers on gonadotropin release.The two gonadotropins were also found to be differently packaged within their corresponding cell types.

View Article: PubMed Central - PubMed

Affiliation: Department of Animal Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.

ABSTRACT
Mammalian pituitaries exhibit a high degree of intercellular coordination; this enables them to mount large-scale coordinated responses to various physiological stimuli. This type of communication has not been adequately demonstrated in teleost pituitaries, which exhibit direct hypothalamic innervation and expression of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in distinct cell types. We found that in two fish species, namely tilapia and zebrafish, LH cells exhibit close cell-cell contacts and form a continuous network throughout the gland. FSH cells were more loosely distributed but maintained some degree of cell-cell contact by virtue of cytoplasmic processes. These anatomical differences also manifest themselves at the functional level as evidenced by the effect of gap-junction uncouplers on gonadotropin release. These substances abolished the LH response to gonadotropin-releasing hormone stimulation but did not affect the FSH response to the same stimuli. Dye transfer between neighboring LH cells provides further evidence for functional coupling. The two gonadotropins were also found to be differently packaged within their corresponding cell types. Our findings highlight the evolutionary origin of pituitary cell networks and demonstrate how the different levels of cell-cell coordination within the LH and FSH cell populations are reflected in their distinct secretion patterns.

No MeSH data available.


Related in: MedlinePlus

Gonadotrope release is differentially mediated by gap-junctions.Perfused tilapia pituitary fragments were stimulated with sGnRHa (arrows) with or without the presence of the gap junction uncoupler meclofenamic acid (MCF, 100 μm, shaded area). LH secretion (a) was significantly affected by MCF whereas FSH cell output (b) was not reduced by gap junction blocker application. Asterisks label the time-points that differ significantly between the two treatments (˙P < 0.05, *p < 0.01, **p < 0.001, ***p < 0.0001). Stars label the time-points that are statistically different from the basal secretion level within the same treatment.
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f3: Gonadotrope release is differentially mediated by gap-junctions.Perfused tilapia pituitary fragments were stimulated with sGnRHa (arrows) with or without the presence of the gap junction uncoupler meclofenamic acid (MCF, 100 μm, shaded area). LH secretion (a) was significantly affected by MCF whereas FSH cell output (b) was not reduced by gap junction blocker application. Asterisks label the time-points that differ significantly between the two treatments (˙P < 0.05, *p < 0.01, **p < 0.001, ***p < 0.0001). Stars label the time-points that are statistically different from the basal secretion level within the same treatment.

Mentions: To find out whether the anatomical contacts are also manifested at the functional level we measured gonadotropin release from tilapia pituitary fragments in the presence of gap-junction blockers. Two gap-junction uncouplers, carbenoxolone and meclofenamic acid (MCF), were used. Stimulation of pituitary fragments by 100 nM sGnRHa induced an approximately sevenfold increase in LH secretion and a twofold increase in FSH secretion by the tissue. Applying gap-junction blockers to perfused pituitary fragments almost completely abolished the response of LH cells to GnRH stimulation (Fig. 3a), whereas the FSH response remained largely unchanged (Fig. 3b). No difference was observed between the effect of MCF or that of carbenoxolone (Supplemental Figure). In control channels, LH generated a statistically significant response 15 minutes after stimulation (Fig. 3a) whereas the increase in FSH levels was significant 45 minutes after stimulation (Fig. 3b).


Anatomical and functional gonadotrope networks in the teleost pituitary.

Golan M, Martin AO, Mollard P, Levavi-Sivan B - Sci Rep (2016)

Gonadotrope release is differentially mediated by gap-junctions.Perfused tilapia pituitary fragments were stimulated with sGnRHa (arrows) with or without the presence of the gap junction uncoupler meclofenamic acid (MCF, 100 μm, shaded area). LH secretion (a) was significantly affected by MCF whereas FSH cell output (b) was not reduced by gap junction blocker application. Asterisks label the time-points that differ significantly between the two treatments (˙P < 0.05, *p < 0.01, **p < 0.001, ***p < 0.0001). Stars label the time-points that are statistically different from the basal secretion level within the same treatment.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4815020&req=5

f3: Gonadotrope release is differentially mediated by gap-junctions.Perfused tilapia pituitary fragments were stimulated with sGnRHa (arrows) with or without the presence of the gap junction uncoupler meclofenamic acid (MCF, 100 μm, shaded area). LH secretion (a) was significantly affected by MCF whereas FSH cell output (b) was not reduced by gap junction blocker application. Asterisks label the time-points that differ significantly between the two treatments (˙P < 0.05, *p < 0.01, **p < 0.001, ***p < 0.0001). Stars label the time-points that are statistically different from the basal secretion level within the same treatment.
Mentions: To find out whether the anatomical contacts are also manifested at the functional level we measured gonadotropin release from tilapia pituitary fragments in the presence of gap-junction blockers. Two gap-junction uncouplers, carbenoxolone and meclofenamic acid (MCF), were used. Stimulation of pituitary fragments by 100 nM sGnRHa induced an approximately sevenfold increase in LH secretion and a twofold increase in FSH secretion by the tissue. Applying gap-junction blockers to perfused pituitary fragments almost completely abolished the response of LH cells to GnRH stimulation (Fig. 3a), whereas the FSH response remained largely unchanged (Fig. 3b). No difference was observed between the effect of MCF or that of carbenoxolone (Supplemental Figure). In control channels, LH generated a statistically significant response 15 minutes after stimulation (Fig. 3a) whereas the increase in FSH levels was significant 45 minutes after stimulation (Fig. 3b).

Bottom Line: We found that in two fish species, namely tilapia and zebrafish, LH cells exhibit close cell-cell contacts and form a continuous network throughout the gland.These anatomical differences also manifest themselves at the functional level as evidenced by the effect of gap-junction uncouplers on gonadotropin release.The two gonadotropins were also found to be differently packaged within their corresponding cell types.

View Article: PubMed Central - PubMed

Affiliation: Department of Animal Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.

ABSTRACT
Mammalian pituitaries exhibit a high degree of intercellular coordination; this enables them to mount large-scale coordinated responses to various physiological stimuli. This type of communication has not been adequately demonstrated in teleost pituitaries, which exhibit direct hypothalamic innervation and expression of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in distinct cell types. We found that in two fish species, namely tilapia and zebrafish, LH cells exhibit close cell-cell contacts and form a continuous network throughout the gland. FSH cells were more loosely distributed but maintained some degree of cell-cell contact by virtue of cytoplasmic processes. These anatomical differences also manifest themselves at the functional level as evidenced by the effect of gap-junction uncouplers on gonadotropin release. These substances abolished the LH response to gonadotropin-releasing hormone stimulation but did not affect the FSH response to the same stimuli. Dye transfer between neighboring LH cells provides further evidence for functional coupling. The two gonadotropins were also found to be differently packaged within their corresponding cell types. Our findings highlight the evolutionary origin of pituitary cell networks and demonstrate how the different levels of cell-cell coordination within the LH and FSH cell populations are reflected in their distinct secretion patterns.

No MeSH data available.


Related in: MedlinePlus