A comparison of certain responses of the vascular system of rats after the administration of progesterone and oestrogen

The effects of progesterone and oestrogens on vascular responses to oxytocin were studied in female rats. Like oestrogens, progesterone caused the appearance of a pressor response to oxytocin, and throughout pseudopregnancy oxytocin acted as a pressor substance. The pressor response to oxytocin was the same, whether progesterone and oestrogen were given singly or together. Eserine abolished the pressor response to oxytocin of rats in natural oestrus or animals treated with an oestrogen, but did not eliminate the pressor response after progesterone.

Heat reactions of male and female Caucasians

Thirty male and twenty-six female Caucasians were tested at work levels of 1.0 liters O2 consumption in 90 F wet-bulb temperature, 93 F dry-bulb temperature, and 80 ft/min air velocity for comparative heat reactions in the unacclimatized state. The females had more severe physiological and psychological reactions. Rectal temperatures of 104 F and heart rates of 180 beat/min were reached more rapidly than in the male. The females sweated less and their oxygen consumptions were lower than those of the males. Ten males and four females were then acclimatized to the same extent at the same work rate in 93 F wet-bulb temperature. At the end of the period their reactions were closely similar, although the females responded slower to the acclimatization procedure. Both groups ended with heart rates of 140 beat/min and rectal temperatures of 102 F. The females, however, continued to sweat less. In a retest at 90 F wet-bulb temperature, both groups had heart rates of 130–140 beat/min and rectal temperatures of 101 F. Females still sweated less. The results demonstrate the fact that females react more severely on exposure to severe heat and work conditions. Once acclimatized, however, the temperature and circulatory reactions of both sexes are closely similar, but the females sweat less than males.

acclimatization of Caucasians to heat; Caucasians—acclimatization to heat; sex differences—heat reactions; physiological reactions to heat

Submitted on September 14, 1964