Alterations in Mast Cell Degranulation and Ovarian Histamine in the Proestrous Hamster 1

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Abstract
Mast cells in the ovary of cyclic hamsters were observed exclusively in the hilum and in the vicinity of blood vessels that enter and exit the ovary. Ovaries were collected on proestrus from hamsters at 0900 h preluteinizing hormone (LH) surge, 1500 h (peak LH surge) and 2100 h (post-LH surge) and processed for routine histologic staining with toluidine blue. A significant increase in the percentage of extensively degranulating mast cells was observed coincident with the gonadotropin surge (0900 h: 5.39 .+-. 0.97%; 1500 h: 20.39 .+-. 2.76%). At the peak of LH surge the ovarian histamine concentration was also significantly higher than those before and after the surge (1500 h: 5.13 .+-. 0.94 ng/mg ovary; 0900 h and 2100 h: 2.84 .+-. 0.35 and 3.02 .+-. 0.48 ng/mg, respectively). A major source of ovarian histamine evidently is mast cells residing in the ovarian hilum and surrounding the ovarian blood vessels that enter and exit the ovary. The gonadotropin surge on the day of proestrus evidently is a trigger for release of mast cell histamine.