Dopamine requires ascorbic acid to be the prolactin release-inhibiting factor

Area of Science:

• Endocrinology
• Cell Biology

Background:

• Dopamine is a key regulator of prolactin secretion from the pituitary gland.
• Prolactin plays a crucial role in lactation and other physiological processes.
• The precise mechanisms underlying dopamine's inhibitory action and its limitations are not fully understood.

Purpose of the Study:

• To investigate the sustained inhibitory effect of dopamine on prolactin release.
• To explore the role of ascorbic acid in modulating dopamine's action on prolactin secretion.
• To examine the impact of dopamine and ascorbic acid on dopamine D2 receptor density in pituitary cells.

Main Methods:

• Primary cultured pituitary cells and GH4ZR7 cell lines were used.
• Perifusion experiments were conducted to assess prolactin release.
• Dopamine and ascorbic acid concentrations were varied to observe their effects.
• Dopamine D2 receptor density was measured.

Main Results:

• High concentrations of dopamine inhibited prolactin release for less than 60 minutes.
• Alternating dopamine and control medium suggested decreased lactotroph sensitivity to dopamine over time.
• Ascorbic acid significantly prolonged dopamine's prolactin-inhibiting effect.
• Dopamine decreased dopamine D2 receptor density, while ascorbic acid inhibited this downregulation.

Conclusions:

• Dopamine alone has limited sustained efficacy in inhibiting prolactin release.
• Ascorbic acid acts as a crucial supplementary agent, enhancing dopamine's prolactin-inhibiting function.
• Ascorbic acid's mechanism involves preventing the downregulation of dopamine D2 receptors, thereby maintaining lactotroph sensitivity.