Endocrine Pathology

, 4:131 | Cite as

Effect of intravenous infusion of growth hormone-releasing hormone on the morphology of rat pituitary somatotrophs

  • Lucia Stefaneanu
  • Kalman Kovacs
  • Eva Horvath
  • Ross G. Clark 
  • Michael J. Cronin 
Original article

Abstract

The effect of GRH infusion on rat adenohypophysial morphology was studied by light microscopy, immunocytochemistry, in situ hybridization, and electron microscopy. Synthetic rat GRH was intravenously administered by osmotic minipumps at 14.4, 72, 360 and 720 μg/ day/rat for 1 week. In one group treated for 1 week with a daily dose of 720 μg GRH, the rats were killed 7 days after withdrawal of GRH. Control rats in which GRH was replaced by excipient, or those that received no treatment, were included as well. GRH infusion with daily doses of 360 and 720 μg resulted in a significant increase in pituitary weight and weaker GH immunoreactivity compared with other groups. Ultrastructurally, the somatotrophs were increased in size and became sparsely granulated, and the organelles involved in hormone sythesis were very prominent. The intensity of the GH mRNA signal did not differ from control animals, suggesting the desensitization of somatotrophs to GRH. The highest GRH dose induced an increased number of nuclei immunoreactive for proliferation cell nuclear antigen (PCNA). One week after GRH withdrawal, shrinkage of cytoplasm, involution of RER and Golgi complex, and a decrease of cell attachment sites indicated the reversibility of changes induced by GRH. In conclusion, GRH infusion induced, within days, hypertrophy and proliferation of somatotrophs with ultrastructural features of highly stimulated, sparsely granulated cells. Morphological changes were reversible.Endocr Pathol 4:131–139, 1993.

Keywords

Growth Hormone Pituitary Adenoma Proliferation Cell Nuclear Antigen Secretory Granule Original Magnification 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Blackwell Scientific Publications, Inc 1993

Authors and Affiliations

  • Lucia Stefaneanu
    • 1
  • Kalman Kovacs
    • 1
  • Eva Horvath
    • 1
  • Ross G. Clark 
    • 2
  • Michael J. Cronin 
    • 2
  1. 1.Department of Pathology, St. Michael’s HospitalUniversity of TorontoTorontoCanada
  2. 2.Department of Endocrine ResearchGenentech Inc.South San FranciscoCalifornia

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