How different procedures of blood removal affect blood progesterone concentration in the cyclic female rat

The effects of different procedures of blood removal on blood progesterone level were studied in female rats throughout the diestrous period of estrous cycle. Unoperated, sham operated, adrenalectomized and ovariectomized females were used. The complete manipulation comprising ether anaesthesia and blood collection lasted 3-4 min. Blood removal in itself did not exceed one minute. Blood progesterone levels appeared to be higher in unoperated, sham operated and ovariectomized females bled by heart puncture or from the abdominal vena cava under ether anaesthesia than in their decapitated counterparts bled without ether anaesthesia. Adrenalectomy prevented this effect from occurring. No difference in blood progesterone concentration was noted between anaesthetized and unanesthetized decapitated unoperated females. It was concluded that some procedures of blood removal under ether anaesthesia might cause a stress-related rise in blood progesterone concentration and that ether anaesthesia was not involved.