Are portal vessels present in the pituitary gland 'veins'? A histological study

Morihiro Yoshida, Richard J. Coombs, Masahiro Kuno, Ikuo Wada, Osamu Horiuchi, Damon C. Herbert, Tsuyoshi Soji, Yoshio Mabuchi

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Male Wistar-Imamichi rats were used for light and electron microscopic study. Prior to the appearance of the pars tuberalis (PT), a small cluster of arteries was found in the area where the gland would appear, while an array of capillaries was noted at the bottom of the median eminence (ME). The epithelial structure comprising the PT was first observed along with slender arteries approximately 1mm behind the optic chiasm on both sides of the ME. Although numerous thin capillaries were present in the hypothalamus, thick capillaries (thought to be portal vessels) showed unusually large luminal diameters and were noted attached to the ME, slightly posterior to the PT. In all specimens serially sectioned in the frontal plane, veins were not detected on either the ME or the pituitary stalk, nor was smooth muscle present in the wall of the thick capillaries. Where the pars tuberalis and the anterior lobe adjoined, clusters of agranular and a few granular cells were noted along with several thick capillaries located on the ventral side of the pituitary. Ultrastructurally, numerous capillaries, which were categorized into two groups, were observed between the agranular cells in the PT. One was thin-walled and randomly arranged while the other was thick-walled and contained fenestrations. At the inter-capillary space, connective tissue and interstitial cells were observed. In the PT, bundles of the neuroendocrine fibers, which contained many electron dense granules and mitochondria, were frequent around the capillaries. The cytoarchitecture of the portal vessels and their functional role are discussed in relation to that previously reported.

Original languageEnglish (US)
Pages (from-to)160-168
Number of pages9
JournalBiomedical Research
Issue number2
StatePublished - Oct 2004


  • Anterior pituitary
  • Neuroendocrine
  • Pars tuberalis
  • Portal vessel
  • Rat

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)


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