Relative Importance of Histamine and Estrogen on Implantation in Rats

Abstract

Exposure of lumina of rat uteri to temperatures of –15 C for 5 min does not obviously alter the histological appearance of the endometrium or the other anatomical components of the uterine wall. In such rats, estrus and mating continue to occur at normal intervals but they do not conceive. In this study the upper or lower half of one horn or one whole horn was frozen, the contralateral horn was left as a control, and the rats were allowed to recover for 15 days. When either the upper or lower half of one horn was frozen and the rats were mated, implantation occurred in the unfrozen portion and in the control horn. The previously frozen portion did not respond to trauma applied to it exclusively, by deciduomata formation, but when the trauma was initiated in the unfrozen portion both the frozen and unfrozen parts showed the decidual reaction. In appropriately prepared, progesterone-treated castrated rats, or postparturient mated rats, implantation could no be induced by local estrogen injection into the previously frozen portion of the horn but did occur in the unfrozen portion and the control horn. In contrast, local infusion of histamine into the lumina of frozen horns permitted implantation, and in other animals deciduoma formation. Both frozen and unfrozen control horns responded to the systemic injection of estrogen by increased weight in the same magnitude. Finally, previously frozen horns were found to contain significantly less histamine than control horns and the former contained an average of 0.5 mast cell, while the unfrozen halves contained 4 and the control horns 3 mast cells per section. These data suggest that the primary factor responsible for the decidual response and for implantation is histamine. It remains unknown whether estrogen causes histamine release (and synthesis?) and whether failure of implantation in frozen horns following estrogen injection and other treatments is due to a deficiency of histamine-forming mast cells. (Endocrinology83: 933, 1968)