Effect of “Stress” on Serum Prolactin and Luteinizing Hormone Levels During the Estrous Cycle of the Rat¹

Abstract

The effect of method of blood col-lection on serum prolactin and LH levels was determined throughout the estrous cycle of the rat. Five animals were decapitated and 5 were bled from the abdominal aorta following lap-arotomy under ether anesthesia at each of the following times during the estrous cycle: 3 PM on diestrus days 1, 2 and 3 and 10 AM and 3 PM on the days of proestrus and estrus. Compared to decapitation, laparotomy and bleeding under ether anesthesia induced 3- to 8-fold increases in serum prolactin values at all times studied dur-ing the estrous cycle except on the afternoon of proestrus, when no further increase in already elevated levels was observed. Ether-laparotomy also elevated prolactin titers in ovariectomized females but not in males. Prolactin levels on the morning of proestrus in animals anesthetized with ether and then decapitated were higher than in decapitated animals but less than in ether-laparotomized animals. Serum concentrations of LH were not affected by any of the procedures employed. Since the response of the prolactin release apparatus to a given noxious stimulus is not constant but, instead, varies according to stage of the estrous cycle or sex of the animal, it is concluded that considerable caution must be exercised in selection of a method of withdrawal of blood for prolactin analysis and in experi-mental manipulation of the animal prior to obtaining blood. (Endocrinology87: 1192, 1970)