Pyridoxal phosphate inhibits pituitary cell proliferation and hormone secretion.
Level 5 - mechanism / opinion, no new human data
Bench research (in vitro rodent cell culture) with no human clinical data.
PubMed 16690808 · doi:10.1210/en.2005-1219
What was done
Investigated the effects of pyridoxal phosphate (PLP, 10–1000 µM) on rodent pituitary tumor cell lines (rat MMQ and GH3, mouse AtT-20) and primary rat pituitary cells. Measured cell proliferation, reversibility upon drug withdrawal, [3H]thymidine incorporation, hormone secretion (growth hormone, prolactin, and ACTH adjusted for cell count), cell-cycle phase distribution, apoptosis rates, and Bcl-2 expression.
What was found
After 4 days, PLP dose-dependently reduced cell numbers by up to 81% in MMQ, 64% in GH3 (P < 0.05), and 90% in AtT-20 cells, with proliferation recovering after PLP withdrawal. High-dose PLP (400–1000 µM) decreased [3H]thymidine incorporation by up to 71% (P < 0.05) and reduced GH, prolactin, and ACTH secretion by approximately 70% at 2 days. In primary rat pituitary cells, 100 µM PLP reduced prolactin secretion by 65% (P < 0.05). PLP increased the proportion of cells in G0-G1 phase, decreased S phase, elevated apoptosis in AtT-20 (28% vs. 6%, P < 0.05) and GH3 cells (26% vs. 3%, P < 0.05), and decreased antiapoptotic Bcl-2 expression.
Why it matters
Shows that the active form of vitamin B6 can directly inhibit pituitary tumor cell growth and hormone production in vitro, providing mechanistic rationale for further preclinical evaluation in pituitary adenomas.
Limits
All findings are limited to in vitro rodent cell lines and primary rat cultures; no in vivo or human data were evaluated. The concentrations tested (100–1000 µM) are supraphysiological, and achievable in vivo tissue concentrations or systemic toxicity were not assessed.
Cited by
- supports Taking P5P (a form of vitamin B6) blunts prolactin and can shorten the sexual refractory period.