Functional Lactotroph Heterogeneity in Lactating Rats and in vitro Modification by 17Beta-Estradiol

Area of Science:

• Endocrinology
• Cell Biology
• Reproductive Biology

Background:

• Lactotrophs, the cells responsible for prolactin secretion, exist in heterogeneous populations.
• Understanding the differential regulation of prolactin release by hormones like 17beta-estradiol, thyrotropin-releasing hormone (TRH), and dopamine is crucial for reproductive physiology.

Purpose of the Study:

• To investigate the heterogeneity of lactotrophs in lactating rats.
• To examine the effects of 17beta-estradiol pretreatment on the responsiveness of different lactotroph subpopulations to TRH and dopamine.

Main Methods:

• Separation of lactotrophs from lactating rat pituitaries using unit gravity sedimentation.
• In vitro culture and assessment of prolactin release using continuous perifusion and reverse hemolytic plaque assay.
• Evaluation of dose-dependent effects of TRH and dopamine on prolactin secretion before and after 17beta-estradiol pretreatment.

Main Results:

• Two lactotroph subpopulations were identified: light fraction cells with high basal prolactin release and heavy fraction cells with low basal release.
• 17beta-estradiol pretreatment significantly increased basal prolactin release and TRH stimulation in light fraction cells, while reducing dopamine inhibition.
• Heavy fraction lactotrophs showed high sensitivity to TRH and lower sensitivity to dopamine; 17beta-estradiol pretreatment enhanced TRH effects and diminished dopamine inhibition in these cells as well.

Conclusions:

• Lactotrophs in lactating rats comprise at least two distinct subpopulations with differing prolactin production and regulatory responses.
• 17beta-estradiol plays a significant role in modulating the sensitivity of lactotrophs to TRH and dopamine, impacting prolactin secretion dynamics.