Microvascular changes in cheek-pouch wounds of oophorectomized hamsters following intramuscular injections of female sex hormones

The increased degree of gingivitis during pregnancy may be ascribed to both the influence of bacterial plaque and the action of sex hormones on the microvascular system. The present investigation was undertaken to elucidate the mechanism behind the changes in vascular structure and function in healthy and in slightly inflamed tissues following an increased blood concentration of estrogens, progesterone and chorionic gonadotropin. The cheek-pouch of oophorectomized female hamsters constituted the experimental model. The animals were oophorectomized 7 days prior to the start of the hormone experiments. A micro-wound was produced surgically in the cheek-pouch to leave a defect area with a slightly damaged vascular bed and a surrounding tissue with unaffected circulation as observed by vital microscopy. Irrigation with Tyrode's solution for 10–15 minutes reversed the inflammatory changes in the defect area. A hormone solution (0.2 ml of 5 mg /ml Stilbol^R or progesterone^R or 0.2 ml of 1,500 I.U./ml Gonadex^R) was injected intramuscularly in the hamster's hind leg either once (short term experiments) or daily during a five day period (long term experiments). Estrogen and chorionic gonadotropin caused only minor vascular changes. When progesterone was added to the circulating blood via the hind leg muscle, the resistance of the wound tissue seemed to be lowered and acute inflammation developed in the defect area. The surrounding tissue was unaffected. The symptoms of Inflammation in the wound were more severe than immediately after the surgical procedure as judged by the degree of swelling of the endothelium lining the veins, the number of leucocytes adhering to the vessel walls and the number of micro-thrombi. The findings are discussed in the light of present knowledge of the effects of female sex hormones on intra vascular and perivascular cell structure and function.